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FM811/812
Microprocessor Reset Circuits
Features
* Feature * Precision Voltage Monitor for 3V, 3.3V or 5V Power Supplies * 6A Supply Current * 140ms Minimum Reset Pulse Width * RESET Remains Valid with VCC as Low as 1.4V * Active Low Manual Reset Input * No External Components * 4-Pin SOT-143 Package
Description
The FM811/FM812 is a low cost microprocessor supervisory circuit that asserts a reset if the power supply drops below a designated threshold or the manual reset pin is forced low. Several different reset thresholds are available to accommodate systems operating at 3V, 3.3V or 5V. The FM811 has an active low RESET output, while the FM812 offers an active high RESET output. The reset output is guaranteed to remain asserted for a minimum of 140ms after VCC has risen above the designated reset threshold. The FM811/FM812 is available in a 4-pin SOT-143.
Preliminary Information
Applications
* * * * * Critical Microprocessor Power Monitoring Portable Equipment Intelligent Instruments Computers & Printers Controllers
Typical Applications
VCC
VCC FM811 FM812 MR RESET (RESET)
VCC
P RESET INPUT
( ) = FM812
Rev. 1.4
PRELIMINARY INFORMATION describes products that are in the design stage. Specifications may change in any manner whatever without notice. Contact Fairchild Semiconductor for current information.
(c)2001 Fairchild Semiconductor Corporation
FM811/812
Pin Assignments
Top View
GND
1
4
VCC
GND
1
4
VCC
FM811
FM812
RESET
2
3
MR
RESET
2
3
MR
Pin Definitions
Pin Number Pin Name FM811 1 2 FM812 1 N/A Ground Pin RESET goes low if VCC falls below the reset threshold and remains asserted for one reset time-out period (140ms min.) after VCC exceeds the reset threshold. RESET goes high if VCC falls below the reset threshold and remains asserted for one reset time-out period (140ms min.) after VCC exceeds the reset threshold. Manual reset input. A logic low on MR forces a reset. The reset will remain asserted as long as MR is held low and for one reset time-out period (140ms min.) after MR goes high. This input can be shorted to ground via a switch or driven from CMOS or TTL logic. Float if unused. Power supply input, 3V, 3.3V, or 5V Description
Preliminary Information
GND RESET
RESET
N/A
2
MR
3
3
VCC
4
4
Internal Block Diagram
VCC
4
Reset Threshold (V)
+ Reset Generator
2
RESET (FM811) RESET (FM812)
MR
3
1
GND
(c)2001 Fairchild Semiconductor Corporation
2
FM811/812
Absolute Maximum Ratings
Parameter Terminal Voltage Input Current Output Current Rate of Rise Operating Temperature Range Storage Temperature Range Lead Temperature Range Power Dissipation (TA = +70C) Symbol VCC MR VCC, MR RESET, RESET VCC TA Ratings -0.3 to 6.0 -0.3 to (VCC + 0.3) 20 20 100 -40 to +85 -65 to +150 300 320 Units V V mA mA V/s C C C mW
Stresses above those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent device failure. Functionality at or above these limits is not implied. Exposure to absolute maximum ratings for extended periods may affect device reliability. Operating ranges define those limits between which the functionality of the device is guaranteed.
Preliminary Information
Electrical Characteristics
VCC = 5V for FM81_L/M/J, VCC = 3.3V for FM81_S/T, VCC = 3V for FM81_R, TA = Operating Temperature Range, unless otherwise noted. Parameter Operating Voltage Range Supply Current, ICC Reset Voltage Threshold, VTH Conditions TA = 0C to 70C TA = -40C to 85C FM811L/M/J, FM812L/M/J VCC < 3.6V, FM811R/S/T, FM812R/S/T FM811L, FM812L FM811M, FM812M FM811J, FM812J FM811T, FM812T FM811S, FM812S FM811R, FM812R Min. 1.4 1.6 Typ. Max. 5.5 5.5 15 10 4.75 4.50 4.10 3.15 3.00 2.70 560 Units V A V
Reset Time-out Period, tR RESET Output Voltage, VOH RESET Output Voltage, VOL
RESET Output Voltage, VOH RESET Output Voltage, VOL MR Minimum Pulse Width MR to Reset Delay MR Input Threshold, VIH MR Input Threshold, VIL MR Pull-Up Resistance MR Glitch Immunity
ISOURCE = 800A, FM811L/M/J ISOURCE = 500A, FM811R/S/T VCC= VTH Min., ISINK = 3.2mA, FM811L/M/J VCC= VTH Min., ISINK = 1.2mA, FM811R/S/T VCC > 1.4V, ISINK = 50A, TA= 0C to 70C VCC > 1.6V, ISINK = 50A, TA= -40C to 85C 1.8V < VCC < VTH Min., ISOURCE = 150A 0.8 x VCC ISINK = 3.2mA, FM810L/M/J ISINK = 1.2mA, FM810R/S/T 10 0.5 VCC > VTH Max., FM81_L/M/J FM81_R/S/T VCC > VTH Max., FM81_L/M/J FM81_R/S/T 2.3 0.7 x VCC
4.50 4.25 3.89 3.00 2.85 2.55 140 VCC - 1.5 0.8 x VCC
9 6 4.63 4.38 4.00 3.08 2.93 2.63 240
ms V V
0.4 0.3 0.3 0.3 0.4 0.3
V V s s V
10
20 100
0.8 0.25xVCC 30
k ns
(c)2001 Fairchild Semiconductor Corporation
3
FM811/812
Circuit Description
Microprocessor Reset
The RESET pin is asserted whenever VCC falls below the reset threshold voltage or if MR (manual reset) is forced low. The reset pin remains asserted for a period of 240ms after VCC has risen above the reset threshold voltage or MR has returned high. The reset function ensures the microprocessor is properly reset and powers up into a known condition after a power failure. RESET will remain valid with VCC as low as 1.4V.
VCC V TH
Interfacing to Bidirectional Reset Pins
The FM811/ FM812 can interface with Ps with bidirectional reset pins by connecting a 4.7k resistor in series with the FM811/ FM812 output and the P reset pin.
VCC
VCC
VCC
FM811 RESET RESET
100k
P
MR
Preliminary Information
tR
RESET
tR
RESET Valid to 0V VCC Transients
A resistor can be added from the RESET pin to ground to ensure the RESET output remains low with VCC down to 0V. A 100k resistor connected from RESET to ground is recommended. The size of the resistor should be large enough to not load the RESET output and small enough to pull-down any stray leakage currents.
The FM811/ FM812 are relatively immune to negativegoing VCC glitches below the reset threshold. Typically, a negative-going transient 125mV below the reset threshold with a duration of 50ms (25ms for FM81_R/S/T) or less will not cause an unwanted reset.
(c)2001 Fairchild Semiconductor Corporation
4
FM811/812
Packaging Information
4-Pin SOT-143
0.079 0.071
0.055 0.047
0.098 0.083
Dimensions are in inches
0.037 0.030
0.021 0.015
Preliminary Information
0.120 0.105 0.040 0.031 0.080 0.070 0.0059 0.0035
0.004 0.001
0.010 0.005
Tape and Reel Information
4.0 0.1 2.0 0.05 O1.5 0.1 1.75 0.1
3.5 0.05 8.0 0.3
O1.1 0.1 4.0 0.1 2.7 0.1 1.2 0.1 3.1 0.1 Dimensions are in millimeters
(c)2001 Fairchild Semiconductor Corporation
5
FM811/812
Ordering Information
PART NUMBER FM811LUX FM811MUX FM811JUX FM811TUX FM811SUX FM811RUX FM812LUX FM812MUX FM812JUX FM812TUX FM812SUX FM812RUX * YY = Lot Code TOP MARKING* KLYY KMYY KJYY KTYY KSYY KRYY LLYY LMYY LJYY LTYY LSYY LRYY RESET THRESHOLD (V) 4.63 4.38 4.00 3.08 2.93 2.63 4.63 4.38 4.00 3.08 2.93 2.63 OUTPUT TYPE Push-Pull, active LOW Push-Pull, active LOW Push-Pull, active LOW Push-Pull, active LOW Push-Pull, active LOW Push-Pull, active LOW Push-Pull, active HIGH Push-Pull, active HIGH Push-Pull, active HIGH Push-Pull, active HIGH Push-Pull, active HIGH Push-Pull, active HIGH PACKAGE 4-Pin, SOT143 4-Pin, SOT143 4-Pin, SOT143 4-Pin, SOT143 4-Pin, SOT143 4-Pin, SOT143 4-Pin, SOT143 4-Pin, SOT143 4-Pin, SOT143 4-Pin, SOT143 4-Pin, SOT143 4-Pin, SOT143 PACKING METHOD 3000 units in T&R 3000 units in T&R 3000 units in T&R 3000 units in T&R 3000 units in T&R 3000 units in T&R 3000 units in T&R 3000 units in T&R 3000 units in T&R 3000 units in T&R 3000 units in T&R 3000 units in T&R
Preliminary Information
DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user.
www.fairchildsemi.com 1/3/02 0.0m 001 Stock#DSxxxxxxxx 2001 Fairchild Semiconductor Corporation
2. A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.

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