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HV857DB1
HV857DB1 EL Lamp Driver
Introduction
The Supertex HV857DB1 demo board contains all necessary circuitry to demonstrate the features of the HV857 EL lamp driver. Simply connect it to a power supply and a lamp. For additional assistance in designing EL driver circuits, please refer to application notes AN-H33 (effect of external components on performance of Supertex EL drivers) and AN-H43 (EL lamp driver circuits to reduce audible lamp noise).
Specifications
Input Voltage Supply Current Lamp Size Range Lamp Frequency Converter Frequency 1.8V to 5.0V 25mA up to 2.6in2 250Hz 80KHz
Board Layout and Connections
VDD Rsw Rel EN GND VIN
+
Cdd
VB
VA
HV857
Cin Cs
LX
D
Demo Board Connections: EN Enable Input
Enables/Disables the lamp driver. A logic high (connect to VDD) enables the driver and a logic low (connect to GND) disables the driver. This input can be connected to a mechanical switch, or to a logic circuit output with a source impedance of less than 20K.
VIN Inductor Supply
Supplies the high voltage power converter. Connect to positive terminal of a power supply.
GND Circuit Ground
Connect to VDD and VIN negative terminals. Supply bypass capacitors for both VDD and VIN are provided on the demo board. External supply bypass capacitors are not required.
VDD IC Supply
Supplies the HV857 EL driver IC. The supplied circuit is optimized for 3.0V operation. The operating range can be from 1.8V to 5.0V. Connect to positive terminal of a power supply.
VA and VB Lamp Connections
Connect to an EL lamp. Polarity is irrelevant.
* Note: Make sure all the above connections are made before powering up the supply voltages.
11/27/01
Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products liability indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be defective due to workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer page on the Supertex website.
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HV857DB1
HV857DB1 Schematic
Enable ON=VDD OFF=0V 1 V DD 2 RSW-osc 3 REL-osc 4 GND HV857MG VA 8 VB 7 EL Lamp CS 6 LX 5 LX= 220H
Cin
+
VDD
560K 2.0M
-
0.1F
Cdd
SB01-15
+
VIN
-
4.7F
CS= 3.3nF 100V
* Note: Tie VDD and VIN together if split supplies are not used.
SB01-15=150V Sanyo Diode Inductor: Murata LQH32CN221K21
Typical Performance
The specific external components used in the above circuit are LX=220H Murata (LQH32CN221K21), Cs= 3.3nF 100V NPO. The following was observed when driving a 2.6in2 Green lamp.
VDD= VIN (V) 1.8 2.0 3.0 4.0 5.0
IIN (mA) 24.3 24.9 24.6 20.3 17.7
VCS (V) 69.6 72.3 85.0 90.0 92.7
fEL (Hz) 250 250 250 250 250
Brightness ft-lm 4.26 5.07 8.09 8.64 8.81 cd/m2 14.6 17.3 27.7 29.6 30.2
The following was observed when driving a 1.7in2 Green lamp.
Brightness ft-lm 4.91 5.76 7.25 7.49 7.54 cd/m2 16.8 19.7 24.8 25.6 25.8
VDD= VIN (V) 1.8 2.0 3.0 4.0 5.0
IIN (mA) 22.1 20.5 17.3 13.7 11.7
VCS (V) 76.3 79.8 89.0 92.0 93.5
fEL (Hz) 250 250 250 250 250
The above circuit may need to be optimized further based on specification of the lamp used.
11/27/01rev.4
(c)2001 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.
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1235 Bordeaux Drive, Sunnyvale, CA 94089 TEL: (408) 744-0100 * FAX: (408) 222-4895 www.supertex.com

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