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SSL3250A
Photo flash dual LED driver
Rev. 03 -- 30 June 2009 Product data sheet
1. General description
The SSL3250A is a photo flash LED driver designed for battery operated mobile devices such as mobile phones and PDAs. The boost converter delivers high performance and drives a single or dual, high brightness LED at up to 500 mA with over 85 % efficiency. The driver can be programmed to operate in Flash, Torch or Indicator / Video-on mode. The small silicon size and the high internal switching frequency of 1.2 MHz minimize the SSL3250A footprint making it very suitable for mobile phones where space is limited, and only requiring four external components. Driving a high power flash LED within its safe operating limits was a concern when the SSL3250A was designed, so a time-out function can be programmed via the I2C interface, which will prevent overstressing the LED. Due to the specific requirements of a mobile phone, the flash current can be rapidly lowered during RF transmit by using optional external setting resistors.
2. Features
I I I I I I I I I I I I I I I High power single, or dual, LED output driving up to 500 mA flash current Separate indicator LED output of 2.5 mA to 20 mA Output voltage of up to 9.5 V Wide input voltage range of 2.7 V to 5.5 V High efficiency, over 85 % at optimum output current Switching frequency of 1.2 MHz Flash, Torch, and Indicator mode supported Internally timed flash operation up to 820 ms I2C-bus, programmable up to 400 kHz Strobe signal to avoid I2C latency for flash Discrete enable signals for stand-alone operation Optional resistor configurable output currents Fast response to accommodate external TxMasking functionality Soft start in Torch and Flash modes to avoid battery overloading Integrated protection circuits for enhanced system reliability N Internal time-out function N OverTemperature Protection (OTP) N UnderVoltage LockOut (UVLO) N OverVoltage Protection (OVP) N Output current protection N Interrupt signaling to system controller I Low device shut-down current, less than 1 A I SOT758-3, thermally enhanced 16 terminal HVQFN package
NXP Semiconductors
SSL3250A
Photo flash dual LED driver
3. Applications
I White LED driver for battery powered portable devices I Photo flash LED driver for mobile phones and digital cameras
4. Ordering information
Table 1. Ordering information Package Name SSL3250AHN/C1 HVQFN16 Description plastic thermal enhanced very thin quad flat package; no leads; 16 terminals; body 3 x 3 x 0.85 mm Version SOT758-3 Type number
4.1 Ordering options
Table 2. Ordering options Orderable part number SSL3250AHN/C1,528 Pin 1 indicator location for tape and reel Pin 1 in quadrant 2. See Figure 1. Type number SSL3250AHN/C1
5. Marking
pin 1 indicator
direction of unreeling
002aae613
Fig 1.
SSL3250AHN/C1,528 with package rotated 90 clockwise with pin 1 in quadrant 2
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SSL3250A
Photo flash dual LED driver
6. Block diagram
VBAT
4.7 F Ceramic
2.2 H
PGND
VIN INTERNAL SUPPLY
I_IND
LX
SSL3250A
VO
IF_SEL SDA/EN1 SCL/EN2 STRB INT ACT PGND R_IND R_FL R_TR I2C INTERFACE AND CONTROL LINEAR CURRENT SINK CURRENT FEEDBACK UP CONVERTER
4.7 F Ceramic
PGND One or two LEDs
LED
Isink
R1
R2
R3
GND
PGND
GND
014aaa286
Fig 2.
Block diagram
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SSL3250A
Photo flash dual LED driver
7. Pinning information
7.1 Pinning
15 ACT terminal 1 index area 16 STRB
14 VIN
13 LX 12 PGND 11 INT 10 IF_SEL 9 LED GND
014aaa363
R_TR R_FL SCL/EN2 SDA/EN1
1 2
SSL3250A
3 4 5 6 7 VO 8
Transparent top view
Fig 3.
Pin configuration (terminal 1 index area is die pad GND)
7.2 Pin description
Table 3. Symbol R_TR R_FL SCL / EN2 SDA / EN1 R_IND I_IND VO GND LED IF_SEL INT PGND LX VIN ACT STRB Die pad Pin description Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Type Analog IO Analog IO I I/O Analog IO Analog I Analog O Ground Analog I I O Ground Analog I Input I I analog Description Setting resistor for torch current Setting resistor for flash current Serial Clock Line (SCL) in I2C mode / Enable 2 in Direct enable mode Serial Data Line (SDL) in I2C mode / Enable 1 in Direct enable mode Setting resistor for indicator current Indicator LED current sink Output voltage Ground Feedback of the main LED current Interface select; choose between direct enable control or I2C Interrupt output (open collector) Power ground Inductor connection Input voltage Activate Strobe signal to enable flash in I2C mode Exposed die pad; connect to GND
SSL3250A_3
R_IND
I_IND
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SSL3250A
Photo flash dual LED driver
8. Functional description
8.1 Introduction
The SSL3250A is an asynchronous boost converter intended to drive either a single high power flash LED or two high power flash LEDs in series. The main LED current is controlled by the output voltage of the boost converter and the integrated linear current sink. The SSL3250A has two interface modes and five operational modes. The control interface is selected by the interface select pin IF_SEL. Depending on the interface mode selected, the device can either be controlled by an I2C interface or by external enable lines. Both interface modes control the five operational modes. These operational modes are:
* * * * *
Shut-down mode Standby mode Indicator mode Torch mode Flash mode
The first mode is entered by putting a LOW level on the activate pin (ACT). This pin is common for both interface modes. The operational modes Torch and Flash apply to the same main LED current source, and the Indicator mode applies to a separate indicator LED current source. Only when the I2C interface mode is enabled, the operational modes Indicator, Flash and/or Torch can be used in parallel. In normal operation, the regulated converter uses Pulse Width Modulation (PWM), so the switching frequency is constant in all modes. In applications where the required main LED voltage is lower than the applied input voltage, the converter switches to linear mode. The excess voltage difference between the required LED voltage and the input voltage is now compensated by increasing the voltage over the current sink and therefore on the LED pin. Apart from the main LED(s), a separate indicator LED can be driven from the SSL3250A. This indicator LED is driven by a linear current sink circuit that operates independently from the switch mode converter for the main LED(s).
8.2 Interface modes
The device is equipped I2C mode and Direct enable mode interfaces. Which interface mode is used, is defined by the level of the IF_SEL pin at the start-up of the device (VACT LOW to HIGH). The state of the IF_SEL pin should be kept static after powering up the device. Table 4 shows the interface possibilities.
Table 4. IF_SEL 0 1 Interface modes Interface mode I2C mode Direct enable mode Relevant controls SDA, SCL, STRB, ACT, R_FL, INT. EN1, EN2, ACT, INT, R_TR, R_FL, R_IND, INT.
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NXP Semiconductors
SSL3250A
Photo flash dual LED driver
8.2.1 Using the direct enable control
When the Direct enable mode is used, the device can be switched to the various operational modes using the ACT, EN1 and EN2 control signals. The definition of these control signals is given in Table 5. The current in the main LED, in Torch mode and Flash mode and the LED current in the indicator LED can be independently controlled by the external current setting resistors R_IND, R_TR and R_FL. When no external current setting resistors are used, the pins should preferably be connected to VIN and the default current levels for each LED.
Table 5. ACT 0 1 1 1 1 Enable definition EN2 X 0 0 1 1 EN1 X 0 1 0 1 Operational mode Shut-down mode Standby mode Indicator mode Torch mode Flash mode LED active Indicator LED Main LED Main LED
The relation between the ACT and EN1, EN2 signals is given in Figure 4. All modes can be entered from the Standby mode. Entering Torch mode or Indicator mode before entering Flash mode is not required.
tstart(soft)
Main LED current Indicator LED current EN1 EN2 ACT Shut-down Standby Indicator Torch Flash Torch Indicator
014aaa294
Fig 4.
Functional description of the SSL3250A
8.2.2 Using the I2C control
Using the I2C mode enables additional features and settings as described in the I2C register set (see Table 6). The I2C mode has the same operational modes as described in Section 8.2.1, Figure 4. The Flash mode is entered in two steps: 1. Set the correct current and timing values in the current control and timing registers. This arms the device for the required flash operation.
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SSL3250A
Photo flash dual LED driver
2. Trigger the Flash mode either by the hardware STRB pin or by the FLASH_STRB bit in the Flash strobe register 02h. When the external strobe pin is not used it should be connected to GND to prevent false strobing of the main LED. The external current setting resistor R_FL can still be used in Flash mode but is not required. When the external current setting resistor R_FL is not used, the pin should preferably be connected to VIN, this way a default resistor value of approximately 50 k is assumed. The current setting resistors for the indicator LED, R_IND and for the Torch mode, R_TR have no function in I2C mode and the pins should preferably be connected to VIN.
8.3 Operational modes
8.3.1 Shut-down mode
The device is in Shut-down mode when the activate pin (ACT) is LOW. In Shut-down mode the internal circuitry of the device is turned off to guarantee a low shut-down current. The N-channel MOSFET (NMOS) is set to high-impedance. To limit the LED current to a minimum leakage, the current sink circuitry for both the main LED and the indicator LED are switched to high-impedance. After making the pin ACT HIGH, the device will start up and is ready to receive commands through the selected interface.
8.3.2 Standby mode
In Standby mode the internal circuitry of the device remains on, but the converter is not switching. The NMOS is set to high-impedance. To limit the LED current to a minimum leakage, the current sink circuitry for both the main LED and the indicator LED are switched to high-impedance. In this mode the device is able to respond to I2C communication.
8.3.3 Torch mode
The Torch mode allows the main LED to be switched on, without timing limitations, at a lower LED current setting. The Torch mode current in the main LED can be set between 50 mA and 200 mA in both the I2C and Direct enable control mode. In I2C mode, the LED current is defined by entering a value between a minimum of 1 and a maximum of 11 in the current control register. In I2C mode the external R_TR resistor is ignored. If an external R_FL resistor is connected, this resistor will also scale down the set torch current. See Section 8.3.6. The current in the main LED using I2C mode is defined using Equation 1. When not using the resistor R_FL, assume a value of 50 k in the equation. Entering Torch mode is done by writing the required current setting in the current control register. The LED will light to the set torch current. Switching off the Torch mode can be done by writing 0h into the current control register, or by entering Flash mode, see Section 8.3.4. 50 k I LED = --------------- + 35 mA + 15 mA x Register R R_FL (1)
When using the Direct enable mode, the torch current is defined by an external resistor connected to the R_TR pin. The LED current is defined using Equation 2. When not using the current set resistor, the torch current will be set to a default level of 125 mA. The
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SSL3250A
Photo flash dual LED driver
default current is equal to connecting an external current set resistor of 50 k. Entering Torch mode in Direct enable mode can be done using the EN1 and EN2 pins. The LED will stay on in Torch mode for as long as the enable pins are set to Torch mode. 50 k I LED = --------------- x 125 mA R R_TR When not using an external resistor, the R_TR pin can be left unconnected, but it is preferably connected to VIN. Never connect the R_TR pin to GND since it will cause unnecessary reference currents to flow to GND. Figure 5 illustrates the Torch mode current setting equation for I2C, while Figure 6 illustrates the Torch mode current setting equation for the Direct enable mode. (2)
200 ILED (mA) 150
100
50
0 0 1 3 5 7 9 11 Torch current using I2C mode Register value
014aaa364
Fig 5.
Torch mode LED current in I2C mode
250 200 ILED (mA) 150 125 100
50
0 125 50 Torch current using direct control mode 31.3 Register value (k)
014aaa365
Fig 6.
Torch mode LED current in Direct enable mode
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NXP Semiconductors
SSL3250A
Photo flash dual LED driver
8.3.4 Flash mode
The Flash mode allows the main LED to be used at high LED current setting. The Flash mode current can be set up to 500 mA in both the I2C and Direct enable mode. In I2C mode, the current is defined by entering a value between a minimum of 12 and a maximum of 31 in the current control register. The external resistor R_FL can be used to scale down the set current. This can be used in the application to enable TxMasking as described in Section 8.3.6. The current in the main LED is defined using Equation 3. When not using the R_FL resistor, assume a resistor value of 50 k in the equation. Entering Flash mode can be done either by using the STRB pin or the FLASH_STRB bit in Flash Strobe register 02h. The duration of the flash can be determined by a timer, STRB triggering or by a time-out. The flash timing is given by Equation 3 and in Section 8.4.2. 50 k I LED = --------------- x ( 35 mA + 15 mA x Register ) R R_FL (3)
When using the Direct enable mode, the flash current can be defined by an external resistor connected to the R_FL pin. The current in the main LED is defined using Equation 4. When not using the current set resistor, the flash current will be set to a default level of 500 mA. The default current is equal to connecting an external current set resistor of 50 k. Entering Flash mode in Direct enable mode can be done using the EN1 and EN2 pins. The LED will stay on in Flash mode for as long as the enable pins are set to Flash mode, but is limited to 820 ms maximum by the time-out timer. 50 k I LED = --------------- x 500 mA R R_FL (4)
When no external current set resistor is used, the R_FL pin can be left unconnected but is preferably connected to VIN. Never connect the R_FL pin to GND as this will cause unnecessary reference currents to flow to GND. Figure 7 illustrates the Flash mode current setting equation for I2C, while Figure 8 illustrates the Flash mode current setting equation for the Direct enable mode.
600 ILED (mA) 500
No Resistor 66.7 100
375
250 215 161 125 110 55 0 0 12 16 20 24 Flash current using I2C mode 28 32
200
Register Value (k)
014aaa366
Fig 7.
SSL3250A_3
Flash mode LED current in I2C mode
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NXP Semiconductors
SSL3250A
Photo flash dual LED driver
600 ILED (mA) 500 400 300 200 100 70 0 357 125 Flash current using direct control mode 50 Resistor Value (k)
014aaa367
Fig 8.
Flash mode LED current in Direct enable mode
8.3.5 Timed Flash mode
The timed operation of the Flash mode can only be used in the I2C interface mode. When the flash is used in Timed mode (bit 4, TO_DEF = 1 in Timer control register 01h), the internal timer will switch off the main LED after the preprogrammed maximum time in the timer control register has expired. The timer starts when the Flash mode is activated either by the software strobe (FLASH_STRB bit in register 02h) or by a LOW to HIGH transition of the hardware strobe (STRB pin) signal. In timed mode strobing of the flash is edge sensitive, therefore the flash time is independent of the level of the software or hardware strobe signal. The flash time is set according to Equation 5: t flash = 820 ms - Register x 54.6 ms (5)
Once the Flash time has expired no interrupt will be generated nor will it be flagged in the status register. A new flash period can be started immediately after the previous timed flash period has expired.
8.3.6 Flash mode during RF transmit
Although the driver is not equipped with a separate TXMASK pin, the device can operate like that to lower the current in the main LED in Flash mode during an RF transmission in a mobile phone application. An external switch can be connected to the resistor controlling the nominal current value for the Flash mode. By lowering the current in the main LED, the inductor current and therefore the current drawn from the battery will be lowered. Reducing the inductor current has to be fast because the inductor current is reduced within 50 s after changing the nominal current level to a lower setting. At the end of the transmission period, the main LED current can be increased again to the nominal current level. A soft start circuit will increase the inductor current with a limited slope as defined by the soft start settings. See Section 8.5.
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SSL3250A
Photo flash dual LED driver
Average inductor current t < 50 s
TxMask Flash
014aaa296
Fig 9.
The inductor current during TxMask
8.3.7 Indicator LED
The indicator LED is connected between the VBAT and the dedicated indicator LED current input pin. Internally a linear current sink controls the indicator LED current to reach the required current level. In I2C mode, the indicator LED current can be set between 2.5 mA and 17.5 mA. The internal 3-bit register sets the actual indicator LED according to the formula in Equation 6. The external resistor R_IND is ignored. I I _IND = Register x 2.5 mA (6)
When using the Direct enable mode, the indicator current can be determined by an external resistor R_IND. The indicator current is defined using Equation 7. It can be set between 2.5 mA and 20 mA. When not using the resistor, the indicator current will be set to a default level of 10 mA. This current is similar to connecting an external resistor of 50 k. Entering Flash mode in Direct enable mode can be done using the EN1 and EN2 pins. The LED will stay on in Flash mode for as long as the enable pins are set. 50 k I I _IND = ----------------- x 10 mA R R_IND (7)
If there is no resistor connected to the R_IND pin, it can either be left unconnected or connected to VIN. Never connect the R_IND pin to GND since it will cause unnecessary reference currents to flow to GND. Figure 10 illustrates the Indicator mode current setting equation for I2C, while Figure 11 illustrates the Indicator mode current setting equation for the Direct enable mode.
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SSL3250A
Photo flash dual LED driver
II_IND (mA) 17.5
12.5
7.5
2.5 0 0 1 3 5 7 Indicator current using I2C mode Register value
014aaa368
Fig 10. Indicator LED currents in I2C mode
22.5 20.0 17.5 II_IND (mA) 12.5 10.0 7.5
3.0 2.5 0 165 50 Indicator current using direct control mode 25 Register value (k)
014aaa369
Fig 11. Indicator LED currents in Direct enable mode
8.4 Protection circuits
There are several protection circuits integrated in the device. These protection circuits protect the device and the application against defects. The SSL3250A has four protection circuits that will inhibit switching of the converter, programming the status register 03h and pulling LOW the interrupt line. The interrupt line, which can be connected to external logic, signaling an error condition. The external logic can read the status register to determine which fault caused the interrupt and decide on the proper action to take. When not using the I2C mode, the status register cannot be read out but the interrupt line still is functional to signal a fault condition.
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SSL3250A
Photo flash dual LED driver
The four protection circuits and their bits in the status register are as follows:
* * * *
Overvoltage protection Time-out protection Overtemperature protection Output short protection
When a protection is triggered, switching of the IC is inhibited without a soft ramp-down of the current in the main LED and also the indicator LED will be switched off. To recover from this fault condition in I2C mode, write 00h to the current control register (00h) to clear the status register release the INT line. After clearing the status register, the current control register can be reloaded and the flash can be retriggered. Reloading the other registers is not necessary as they will not lose their value when an interrupt is generated. In Direct enable mode the status register is cleared and the INT line is released, by making both the EN1 and EN2 pins lO.
8.4.1 Overvoltage protection
If the output voltage (VO) exceeds its limit (Vovp, see Table 9), switching of the converter is inhibited. The output voltage will exceed Vovp limit when no LEDs are connected between pins VO and LED. In some cases an overvoltage protection may occur when the LED pin is shorted to GND during the period a Flash is generated. The converter is trying to compensate for the loss of feedback current by increasing VO. When an overvoltage is encountered, the OVPtrig flag (bit 0) is set in the status register.
8.4.2 Untimed Flash mode
To avoid overloading of the main LED during a flash in Direct enable mode or I2C control mode in untimed Flash mode (bit 4, TO_DEF = 0 in Timer control register 01h). A time-out timer limits the maximum ON time of the flash. In both control modes the flash time-out time is set to a fixed level of 820 ms. When the flash strobe signal is set to LOW in I2C control mode, bit 0 in register 02h is set to 0. When the EN1 signal is set to LOW before the time-out timer has expired in Direct enable mode, the time-out timer is reset. When a time-out situation is encountered, the TOtrig flag (bit 1) is set in the status register. See also Section 8.3.5.
8.4.3 Overtemperature protection
If the chip temperature exceeds its limit (Totp, see Table 9), switching of the converter is inhibited until the temperature drops below its limit minus a small hysteresis. When an overtemperature situation is encountered, the OTtrig flag (bit 2) is set in the status register.
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SSL3250A
Photo flash dual LED driver
8.4.4 Short circuit protection
To prevent device and battery overloading, the converter is short circuit protected. In case the LED pin is shorted to GND due to an application failure, the switching of the converter is inhibited. Typical response times between detection of the LED pin shorted to GND and inhibit switching of the converter is less than 1 ms. The short circuit protection is functional at any time during Torch mode and also during the soft start phase of the flash period. The short circuit protection may also be triggered when either the inductor or the diode is not connected. Also, a shorted diode may trigger the output short protection, if two LEDs are connected in series between VO and LED pins. Therefore little or no current will flow through the LEDs or into the LED pin and VLED will stay almost at GND level. When an overvoltage is encountered, the OS_PROT flag (bit 3) is set in the status register. Remark: If VBAT is HIGH and only one White LED is connected between VO and LED pins, the Schottky diode may be irreversibly damaged when the LED pin is shorted. This is inherent to the asynchronous boost converter topology.
8.4.5 Interrupt line
The interrupt pin INT is an active LOW open-drain output allowing for multiple devices to be connected as a wired OR, using the same interrupt line to the external control logic. On the interrupt line, only one pull-up resistor is needed in the complete system.
8.4.6 Undervoltage lockout
As a result of a low battery voltage, the input voltage can drop too low to guarantee normal operation. When the input voltage has dropped below the undervoltage lockout level, the device switches to an undervoltage lockout state stopping all operations of the device. Start-up is only possible by crossing the start-up level again. Recovering from this error results in the loss of all register settings. This protection does not generate an interrupt on the INT line nor is it flagged in the status register 03h.
8.5 Soft start
To avoid battery overloading when entering the Torch mode or the Flash mode, the device is equipped with a soft start circuit. This circuit limits the rate of rise of the LED current to 4.5 mA/s until the required LED current has been reached. When the device ends Flash mode or Torch mode, the LED current decreases with a controlled slope of 9 mA/s. Whenever a protection is activated, the LED current decreases without the controlled slope and drops immediately to zero.
8.6 Peak current limit
To avoid saturation of the inductor, the device is equipped with a peak current limit function. This circuit limits the peak inductor currents to 2.2 A. No protection is activated.
8.7 I2C-bus protocol
The I2C interface is a 2-wire serial interface developed by NXP Semiconductors to communicate between different ICs or modules. The two wires are an SDA wire and an SCL wire. Both lines must be connected to a positive supply via a pull-up resistor when
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Product data sheet
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SSL3250A
Photo flash dual LED driver
connected to the output stages of a device. Data transfer may only be initiated when the bus is not busy. The SSL3250A I2C bus characteristic is according to the 400 kbit/s Fast-mode I2C from the I2C-bus specification. Remark: For more details on the I2C standard, refer to the document UM10204, "I2C-bus specification and user manual", version 0.3, June 2007, which can be downloaded from the NXP web site (www.nxp.com). The following describes the protocols used by the SSL3250A for the read and write sequences. The read sequence may use a repeated start condition during the sequence to avoid that the bus is released during the communication. The sequences can be used to read or write only one data byte or to read or write a sequence of data bytes. Figure 12 shows a write sequence for a single byte write. Figure 13 show the read sequence for a single byte.
S
Slave address
W
A
Sub address n
A
nth Register
A
P
From master to slave S = START condition P = STOP condition A = Acknowledge N = Not Acknowledged
014aaa292
From slave to master
Fig 12. Single byte I2C write sequence
S
Slave address
W
A
Sub address n
A
Sr
Slave address
R
A
nth Register
N
P
From master to slave
From slave to master
S = START condition P = STOP condition A = Acknowledge N = Not Acknowledged Sr = Start repeat
014aaa290
Fig 13. Single byte I2C read sequence
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SSL3250A
Photo flash dual LED driver
8.7.1 Addressing
Each SSL3250A in an I2C-bus system is activated by sending a valid address to the device. The address always has to be sent as the first byte after the start condition in the I2C-bus protocol Figure 14.
MSB 0 1 1 0 0 0
LSB 0 R W
014aaa288
Fig 14. I2C slave address
There is one address byte required since 7-bit addresses are used. The last bit of the address byte is the read/write-bit and should always be set according to the required operation. This 7-bit I2C address is 0110000b (30h). The 7-bit address plus the R/W bit create an 8-bit write address of 60h and a read address of 61h. The second byte sent to the SSL3250A is the subaddress of a specific register.
8.7.2 Data
After the subduers have been sent the data byte(s) are sent. The definition of the data byte(s) is given in Figure 12. After each data byte an acknowledge is given and the subduers is automatically incremented to the next subduers. A description of the data that can be programmed in the registers is given in the register map in Section 8.7.3.
8.7.3 Register map
Table 6. Description of registers Legend: * default register value Address 00h Register Current control Bit 7 to 3 Symbol MAIN_LEVEL Access R/W Value 00000* 00001 00010 ..... 01010 01011 01100 01101 ..... 11110 11111 2 to 0 IND_LEVEL R/W 000* 001 011 ..... 111
SSL3250A_3
Description Off (default) Torch mode, see Section 8.3.3 Torch mode, see Section 8.3.3 ..... Torch mode, see Section 8.3.3 Torch mode, see Section 8.3.3 Flash mode (armed), see Section 8.3.4 Flash mode (armed), see Section 8.3.4 ..... Flash mode (armed), see Section 8.3.4 Flash mode (armed), see Section 8.3.4 Off (default) Indicator on, 2.5 mA Indicator on, 5 mA Indicator on, 17.5 mA
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SSL3250A
Photo flash dual LED driver
Table 6. Description of registers ...continued Legend: * default register value Address 01h Register Timer control Bit 7 to 5 4 3 to 0 Symbol Reserved TO_DEF TO Access R/W R/W Value 0* 1 0000* 0001 ..... 1110 1111 02h Flash strobe 7 to 1 0 03h Status 7 to 4 3 2 Reserved 0* 1 Reserved OStrig OTPtrig R R 0* 1 0* 1 1 0 TOtrig OVPtrig R R 0* 1 0* 1 LED not shorted to GND LED shorted to GND Temperature < maximum temperature Temperature > maximum temperature; Protection triggered Flash time < Time-out Flash time > Time-out, Protection triggered VO < Vovp VO > Vovp, protection triggered FLASH_STRB R/W Select time-out limit (default) Select timed operation 820 ms (default) 765 ms ..... 56 ms 1 ms Enable flash Description
9. Application design-in information
9.1 Input capacitor
For good input voltage decoupling a low ESR ceramic capacitor is highly recommended. A 4.7 F (X5R/X7R) 6.3 V is the minimum recommended value. Since the input capacitor is supplying the input ripple current, a larger capacitor will improve transient behavior of the regulator and EMI behavior of the power supply. Taking the capacitor DC bias and the temperature derating specifications into account, a 10 F (X5R/X7R) is preferred. Although it is increasing the component count, a smaller capacitor of 100 nF (X5R/X7R) placed in parallel to the input capacitor will also improve EMI behavior. When the circuit is used in other than battery powered applications and the input capacitor is located relatively far from the DC buffer capacitors, it is recommended to add a 150 F tantalum or a 470 F electrolytic capacitor in parallel near the input capacitor.
9.2 Output capacitor
The output capacitor supplies the current to the main LED, while the inductor is being charged, and it also ensures loop stability. The minimum capacitance for stable loop operation would be 2.2 F, but taking the capacitor DC bias and the temperature derating specifications into account, a low ESR ceramic capacitor of 4.7 F (X5R/X7R) is highly recommended. A higher value of capacitance will improve output current ripple, while
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SSL3250A
Photo flash dual LED driver
maintaining loop stability. The SSL3250A overvoltage limit on VO is 10.3 V (typ). The rated voltage of the output capacitor should be at least 16 V. For solution size reasons lower value ceramic capacitors could be placed in parallel.
9.3 Inductor
The device has been designed to operate well with inductance values between 1.5 H and 3.3 H, in order to optimize for solution size. In a typical high current dual flash LED application a 2.2 H inductance is recommended. The inductors saturation current should be greater than or equal to the inductor peak current limiter current, which is typical 2.2 A. During normal operation, it is recommended to keep the inductor peak current below this value. The copper losses and magnetic hysteresis losses in the inductor also contribute to the total system losses.
9.4 Rectifier diode
Selecting a Schottky diode with low forward voltage drop improves efficiency. Although the average current through the diode is equal to the load current and independent on duty cycle for a boost converter topology, it is recommended to select a diode with an average current rating that is significantly higher. The peak current rating of the diode should be greater than the peak current through the inductor.
9.5 PCB layout
It is essential to have a good circuit layout to maximize efficiency and minimize EMI disturbance. Because the circuit topology uses an inductor, it is often appointed as a main source for EMI disturbance. But any loop of wire carrying a current is essentially an electromagnet with a field strength that is proportional to the current. Therefore careful circuit layout is important, keeping loop areas small and minimizing magnetic flux. Due to the way an asynchronous boost converter operates, there are two power states. One state is when the internal NMOS switch is on and one when the NMOS switch is off. During each state there will be a current loop made by the power components that are conducting. Arrange the input capacitor, rectifier diode and output capacitor in such a way around the SSL3250A that during each of the two states the current loop is conducting in the same direction. This prevents phase reversal of the magnetic field and reduces radiated EMI. The current loop area should be kept small by placing the power components as close as possible to the SSL3250A. Use ground planes to keep loop areas to a minimum. Priority should be given to positioning the output capacitor and the rectifier diode as close as possible to the LX and PGND nodes of the SSL3250A. Since large currents will flow from the input capacitor to the inductor and not into the VIN pin of the SSL3250A, it is wise to locate the input capacitor near the inductor. The VIN pin should be star connected to the positive pad of the input capacitor. It is recommended to place an extra 100 nF capacitor from VIN to GND directly next to the SSL3250A. PGND and GND of the SSL3250A should be directly connected to each other preferably by using the die pad area under the SSL3250A. Place the ground connection of the output capacitor as close as possible to the PGND pin of the SSL3250A.
SSL3250A_3
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Product data sheet
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SSL3250A
Photo flash dual LED driver
If the SSL3250A is used in Direct enable mode and external resistors are used, place the external resistors near the SSL3250A, to minimize disturbance on the output current. Connect the other end of the resistors to a `clean' ground, that is ground that is not carrying any large currents. It is preferable to connect all resistor grounds to one trace and connect that trace to the GND pin of the SSL3250A. The preferred minimum trace width for the high current width is 15 mil per Ampere.
10. Limiting values
Table 7. Limiting values In accordance with the Absolute Maximum Rating System (IEC 60134).Voltages referenced to GND. Symbol VI VACT VSDA VEN1 VSCL VEN2 VSTRB VIF_SEL VINT VI_IND VLED VO VLX VR_IND VR_TR VR_FL VPGND Ptot Tj Tamb Tstg VESD Parameter input voltage voltage on pin ACT voltage on pin SDA voltage on pin EN1 voltage on pin SCL voltage on pin EN2 voltage on pin STRB voltage on pin IF_SEL voltage on pin INT voltage on pin I_IND voltage on pin LED output voltage voltage on pin LX voltage on pin R_IND voltage on pin R_TR voltage on pin R_FL voltage on pin PGND total power dissipation junction temperature ambient temperature storage temperature electrostatic discharge voltage class 2 human body model; all pins machine model; all pins charged-device model; all pins
[1] [2] [3]
[2]
Conditions
Min -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5
Max +5.5 VI VI VI VI VI VI VI VI VI VO[1] +20[1] +20[1] VI VI VI +0.5 1.0 +150 +85 +150 2000 150 500
Unit V V V V V V V V V V V V V V V V V W C C C V V V
Tamb = 85 C
-40 -40 -40 -
[2]
[3]
Tolerant to the specified maximum voltage while operating. Do not apply voltages externally; this may cause permanent damage to the device. Equivalent to discharging a 200 pF capacitor through a 0.75 H coil and a 10 resistor. Equivalent to discharging the device (charged with > 10 M resistor) through a 1 measurement resistor.
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Product data sheet
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Photo flash dual LED driver
11. Thermal characteristics
Table 8. Symbol Rth(j-a) Thermal characteristics Parameter thermal resistance from junction to ambient Conditions Based on modeling on a four layer board in free air and five thermal vias under the IC.[1] Typ 63 Unit K/W
[1]
The junction to ambient thermal resistance is dependent on the board layout, PCB material application, and environmental conditions.
12. Characteristics
Table 9. Characteristics VI = 3.0 V to 5.5 V; Tamb = -40 C to +85 C, unless otherwise specified. Symbol VI VI(extnd)(VIN) VI(UVLO) Vhys(UVLO) Parameter input voltage extended input voltage on pin VIN undervoltage lockout input voltage undervoltage lockout hysteresis voltage shutdown current leakage current on pin LX peak current limiter current on pin LX voltage on pin R_IND voltage on pin R_TR voltage on pin R_FL voltage on pin R_IND voltage on pin R_TR voltage on pin R_FL external resistance on pin R_IND external resistance on pin R_TR external resistance on pin R_FL IF_SEL = 1; Resistors used IF_SEL = 1; Resistors used IF_SEL = 1 or 0; Resistors used VI falling VI rising Conditions on pin VIN
[2]
Min 3.0 2.75 2.55 50
Typ[1] 2.65 100
Max 5.5 5.5 2.8 150
Unit V V V mV
General voltage levels
General current levels Isd Ileak(LX) Ilmtr(IM)(LX) Shut-down mode; ACT = 0 ACT = 0 Inductor peak current limiter 2.2 1 0.5 2.4 A A A
Output voltages on external resistor pins VR_IND VR_TR VR_FL VR_IND VR_TR VR_FL Rext(R_IND) Rext(R_TR) Rext(R_FL) Independent of load Independent of load Independent of load
[3] [3] [3]
1.17 1.17 1.17 1.4 1.4 1.4 25 25 50
1.22 1.22 1.22 -
1.27 1.27 1.27 VI VI VI 165 200 357
V V V V V V k k k
Allowed input voltages on external resistor pins
[3] [3] [3]
External resistors
[3][4] [5] [3][4] [5] [3][4] [5]
SSL3250A_3
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Product data sheet
Rev. 03 -- 30 June 2009
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SSL3250A
Photo flash dual LED driver
Table 9. Characteristics ...continued VI = 3.0 V to 5.5 V; Tamb = -40 C to +85 C, unless otherwise specified. Symbol VO ILED Parameter output voltage LED current Conditions on pin VO IF_SEL = 0; current control register = 08h; STRB = 0 IF_SEL = 0; current control register = 30h; STRB = 0 IF_SEL = 0; current control register = C0h; STRB = 1 IF_SEL = 0; current control register = F8h; STRB = 1 default flash current; IF_SEL = 1; EN1 = 1; EN2 = 1; R_FL = High default torch current; IF_SEL = 1; EN1 = 0; EN2 = 1; R_TR = High Ileak(LED) VLED Vovp II_IND leakage current on pin LED voltage on pin LED overvoltage protection voltage current on pin I_IND IF_SEL = 0 (I2C) IF_SEL = 1 (direct enable) default indicator current; IF_SEL = 1; EN1 = 1; EN2 = 0; R_IND = High II_IND Ileak(I_IND) RDSon Timing fsw max tstart(soft) tto(acc) switching frequency maximum duty cycle soft start time accuracy of time-out time ACT = 0 to ACT = 1 response time the absolute value can be set with I2C 1.08 10 1.2 160 1.32 82 400 10 MHz % s % current variation on pin I_IND leakage current on pin I_IND drain-source on-state resistance ACT = 0; Shut-down mode NFET ACT = 0; Shut-down mode boost mode; ILED = 0.5 A follower mode Indicator LED parameters 2.5 2.5 10 17.5 20 mA mA mA
[7] [7] [3] [6]
Min 40
Typ[1] 50
Max 9.5 60
Unit V mA
High power LED parameters
106
125
144
mA
356
395
435
mA
450
500
550
mA
450
500
550
mA
[3]
106
125
144
mA
350 9.8
300 10.5
0.5 11.0
A mV mV V
-
200
15 1 425
% A mW
Power MOSFET
SSL3250A_3
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Product data sheet
Rev. 03 -- 30 June 2009
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NXP Semiconductors
SSL3250A
Photo flash dual LED driver
Table 9. Characteristics ...continued VI = 3.0 V to 5.5 V; Tamb = -40 C to +85 C, unless otherwise specified. Symbol I2C VIL VIH VOL fSCL VIL VIH VIL VIH VOL IIH Temperature Tamb Totp Totp(hys) ambient temperature overtemperature protection trip overtemperature protection trip hysteresis temperature rising temperature falling -40 +25 150 20 +85 C C C interface LOW-level input voltage HIGH-level input voltage LOW-level output voltage SCL clock frequency LOW-level input voltage HIGH-level input voltage LOW-level input voltage HIGH-level input voltage LOW-level output voltage HIGH-level input current digital digital IF_SEL pin IF_SEL pin Isink = 3 mA Isink = 3 mA 1.2 0 0 0 1.2 0 0.5VI 0 0 0.5 VIN 0.4 400 0.5 0.5VI VI 0.4 0.5 V V V kHz V V V V V A Parameter Conditions Min Typ[1] Max Unit
Digital levels: EN1, EN2, STRB, ACT
Digital levels: IF_SEL pin
Digital levels: INT
[1] [2]
All typical values are measured at Tamb = 25 C and VI = 3.6 V. When operating in an extended input voltage range, the device will be fully functional but has a reduced performance specification on certain parameters. An extended input voltage range is entered when the input voltage is dropping below 3.0 V, assuming the device is not in undervoltage lockout mode. When no external resistor is connected, the device will apply a default current setting. See Section 8.3 for details. Corresponding pins should then be connected to high (> 1.4 V) Higher resistor values than the maximum are considered as no resistor is connected and therefore result in the default current setting. Lower resistor values than the minimum will result in large currents being drawn from the device resulting in bad operation. To accommodate two LEDs with a spread in VF between 2.7 V and 4.3 V each. Only valid in Boost mode: typically in a dual LED configuration. When in linear mode, used in specific cases of single LED applications, excess voltage will fall over the LED pin.
[3] [4] [5] [6] [7]
SSL3250A_3
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Product data sheet
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SSL3250A
Photo flash dual LED driver
13. Package outline
HVQFN16: plastic thermal enhanced very thin quad flat package; no leads; 16 terminals; body 3 x 3 x 0.85 mm
SOT758-3
D D1
B A
terminal 1 index area E1 E A
A4
c A1 detail X
e1 e 1/2 e b
5 8
v w
M M
CAB C
C y1 C y
L
4 9
e Eh 1/2 e
1 12
e2
terminal 1 index area
16 13
Dh
X
0
2.5 scale
5 mm
DIMENSIONS (mm are the original dimensions) UNIT mm A max 0.9 A1 0.05 0.00 A4 0.7 0.6 b 0.30 0.18 c 0.2 D 3.1 2.9 D1 2.85 2.65 Dh 1.6 1.4 E 3.1 2.9 E1 2.85 2.65 Eh 1.6 1.4 e 0.5 e1 1.5 e2 1.5 L 0.5 0.3 v 0.1 w 0.05 y 0.05 y1 0.1
OUTLINE VERSION SOT758-3
REFERENCES IEC JEDEC MO-220 JEITA
EUROPEAN PROJECTION
ISSUE DATE 07-10-11 08-02-08
Fig 15. Package outline SOT758-3 (HVQFN16)
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Product data sheet
Rev. 03 -- 30 June 2009
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NXP Semiconductors
SSL3250A
Photo flash dual LED driver
14. Abbreviations
Table 10. EMI ESR IC IO LED MOSFET NMOS PDA PWM RF Abbreviations Description ElectroMagnetic Interference Equivalent Series Resistance Integrated Circuit Input/Output Light Emitting Diode Metal-Oxide Semiconductor Field-Effect Transistor N-type Metal-Oxide Semiconductor Personal Digital Assistants Pulse Width Modulation Radio Frequency Abbreviation
15. Revision history
Table 11. Revision history Release date 20090630 Data sheet status Product data sheet Change notice Supersedes SSL3250A_2 Document ID SSL3250A_3 Modifications:
* *
Section 4.1 "Ordering options": removed orderable part number SSL3250AHN/C1,518 Section 5 "Marking": removed (old) Figure 1 "SSL3250AHN/C1,518 with pin 1 according to EIA-481-C in quadrant 1" Product data sheet Product data sheet SSL3250A_1 -
SSL3250A_2 SSL3250A_1
20090421 20090205
SSL3250A_3
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Product data sheet
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NXP Semiconductors
SSL3250A
Photo flash dual LED driver
16. Legal information
16.1 Data sheet status
Document status[1][2] Objective [short] data sheet Preliminary [short] data sheet Product [short] data sheet
[1] [2] [3]
Product status[3] Development Qualification Production
Definition This document contains data from the objective specification for product development. This document contains data from the preliminary specification. This document contains the product specification.
Please consult the most recently issued document before initiating or completing a design. The term `short data sheet' is explained in section "Definitions". The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status information is available on the Internet at URL http://www.nxp.com.
16.2 Definitions
Draft -- The document is a draft version only. The content is still under internal review and subject to formal approval, which may result in modifications or additions. NXP Semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall have no liability for the consequences of use of such information. Short data sheet -- A short data sheet is an extract from a full data sheet with the same product type number(s) and title. A short data sheet is intended for quick reference only and should not be relied upon to contain detailed and full information. For detailed and full information see the relevant full data sheet, which is available on request via the local NXP Semiconductors sales office. In case of any inconsistency or conflict with the short data sheet, the full data sheet shall prevail.
damage. NXP Semiconductors accepts no liability for inclusion and/or use of NXP Semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customer's own risk. Applications -- Applications that are described herein for any of these products are for illustrative purposes only. NXP Semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. Limiting values -- Stress above one or more limiting values (as defined in the Absolute Maximum Ratings System of IEC 60134) may cause permanent damage to the device. Limiting values are stress ratings only and operation of the device at these or any other conditions above those given in the Characteristics sections of this document is not implied. Exposure to limiting values for extended periods may affect device reliability. Terms and conditions of sale -- NXP Semiconductors products are sold subject to the general terms and conditions of commercial sale, as published at http://www.nxp.com/profile/terms, including those pertaining to warranty, intellectual property rights infringement and limitation of liability, unless explicitly otherwise agreed to in writing by NXP Semiconductors. In case of any inconsistency or conflict between information in this document and such terms and conditions, the latter will prevail. No offer to sell or license -- Nothing in this document may be interpreted or construed as an offer to sell products that is open for acceptance or the grant, conveyance or implication of any license under any copyrights, patents or other industrial or intellectual property rights. Export control -- This document as well as the item(s) described herein may be subject to export control regulations. Export might require a prior authorization from national authorities.
16.3 Disclaimers
General -- Information in this document is believed to be accurate and reliable. However, NXP Semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. Right to make changes -- NXP Semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. This document supersedes and replaces all information supplied prior to the publication hereof. Suitability for use -- NXP Semiconductors products are not designed, authorized or warranted to be suitable for use in medical, military, aircraft, space or life support equipment, nor in applications where failure or malfunction of an NXP Semiconductors product can reasonably be expected to result in personal injury, death or severe property or environmental
16.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners. I2C-bus -- logo is a trademark of NXP B.V.
17. Contact information
For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com
SSL3250A_3
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Product data sheet
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SSL3250A
Photo flash dual LED driver
18. Contents
1 2 3 4 4.1 5 6 7 7.1 7.2 8 8.1 8.2 8.2.1 8.2.2 8.3 8.3.1 8.3.2 8.3.3 8.3.4 8.3.5 8.3.6 8.3.7 8.4 8.4.1 8.4.2 8.4.3 8.4.4 8.4.5 8.4.6 8.5 8.6 8.7 8.7.1 8.7.2 8.7.3 9 9.1 9.2 9.3 9.4 9.5 10 11 12 General description . . . . . . . . . . . . . . . . . . . . . . 1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Ordering information . . . . . . . . . . . . . . . . . . . . . 2 Ordering options . . . . . . . . . . . . . . . . . . . . . . . . 2 Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pinning information . . . . . . . . . . . . . . . . . . . . . . 4 Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 4 Functional description . . . . . . . . . . . . . . . . . . . 5 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Interface modes . . . . . . . . . . . . . . . . . . . . . . . . 5 Using the direct enable control . . . . . . . . . . . . . 6 Using the I2C control. . . . . . . . . . . . . . . . . . . . . 6 Operational modes . . . . . . . . . . . . . . . . . . . . . . 7 Shut-down mode. . . . . . . . . . . . . . . . . . . . . . . . 7 Standby mode. . . . . . . . . . . . . . . . . . . . . . . . . . 7 Torch mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Flash mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Timed Flash mode . . . . . . . . . . . . . . . . . . . . . 10 Flash mode during RF transmit . . . . . . . . . . . 10 Indicator LED . . . . . . . . . . . . . . . . . . . . . . . . . 11 Protection circuits . . . . . . . . . . . . . . . . . . . . . . 12 Overvoltage protection . . . . . . . . . . . . . . . . . . 13 Untimed Flash mode. . . . . . . . . . . . . . . . . . . . 13 Overtemperature protection . . . . . . . . . . . . . . 13 Short circuit protection . . . . . . . . . . . . . . . . . . 14 Interrupt line . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Undervoltage lockout . . . . . . . . . . . . . . . . . . . 14 Soft start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Peak current limit . . . . . . . . . . . . . . . . . . . . . . 14 I2C-bus protocol . . . . . . . . . . . . . . . . . . . . . . . 14 Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Register map . . . . . . . . . . . . . . . . . . . . . . . . . 16 Application design-in information . . . . . . . . . 17 Input capacitor . . . . . . . . . . . . . . . . . . . . . . . . 17 Output capacitor . . . . . . . . . . . . . . . . . . . . . . . 17 Inductor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Rectifier diode. . . . . . . . . . . . . . . . . . . . . . . . . 18 PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Limiting values. . . . . . . . . . . . . . . . . . . . . . . . . 19 Thermal characteristics. . . . . . . . . . . . . . . . . . 20 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 20 13 14 15 16 16.1 16.2 16.3 16.4 17 18 Package outline . . . . . . . . . . . . . . . . . . . . . . . . Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . Revision history . . . . . . . . . . . . . . . . . . . . . . . Legal information . . . . . . . . . . . . . . . . . . . . . . Data sheet status . . . . . . . . . . . . . . . . . . . . . . Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . Disclaimers. . . . . . . . . . . . . . . . . . . . . . . . . . . Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . Contact information . . . . . . . . . . . . . . . . . . . . Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 24 24 25 25 25 25 25 25 26
Please be aware that important notices concerning this document and the product(s) described herein, have been included in section `Legal information'.
(c) NXP B.V. 2009.
All rights reserved.
For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com Date of release: 30 June 2009 Document identifier: SSL3250A_3

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