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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).
Board Layout and Connections
V
DD
Rsw
Rel
EN
GND
+
Cdd
Cin
Specifications
Input Voltage 1.8V to 5.0V
Supply Current 25mA
Lamp Size Range up to 2.6in
Lamp Frequency 250Hz
Converter Frequency 80KHz
V
HV857
B
Cs
V
A
2
L
V
IN
X
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
20KΩ.
V
IC Supply
DD
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.
* Note: Make sure all the above connections are made before powering up the supply voltages.
D
V
Inductor Supply
IN
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.
VA and V
Connect to an EL lamp. Polarity is irrelevant.
Lamp Connections
B
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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ON=V
OFF=0V
HV857DB1
HV857DB1 Schematic
Enable
DD
+
V
DD
-
0.1µF
C
560KΩ
2.0M
Ω
dd
+
V
IN
-
* Note: Tie VDD and VIN together if split supplies are not used.
C
4.7µF
in
1
2
3
4
V
R
R
GND
DD
SW-osc
EL-osc
HV857MG
8
V
A
V
7
B
C
6
S
L
5
X
SB01-15=150V Sanyo Diode
Inductor: Murata LQH32CN221K21
SB01-15
LX=
220µH
CS=
3.3nF
100V
EL Lam
p
Typical Performance
The specific external components used in the above circuit are LX=220µH Murata (LQH32CN221K21), Cs= 3.3nF 100V NPO.
The following was observed when driving a 2.6in2 Green lamp.
VDD=
V
NI
)V(
)Am(V
I
NI
)V(fLE)zH(
SC
ml-tfm/dc
8.13.426.9605262.46.41
0.29.423.2705270.53.71
0.36.420.5805290.87.72
0.43.020.0905246.86.92
0.57.717.2905218.82.03
ssenthgirB
2
2
The following was observed when driving a 1.7in
VDD=
V
NI
)V(
I
NI
Green lamp.
)Am(V
)V(fLE)zH(
SC
ml-tfm/dc
8.11.223.6705219.48.61
0.25.028.9705267.57.91
0.33.710.9805252.78.42
0.47.310.2905294.76.52
0.57.115.3905245.78.52
The above circuit may need to be optimized further based on specification of the lamp used.
1235 Bordeaux Drive, Sunnyvale, CA 94089
©2001 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.
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TEL: (408) 744-0100 • FAX: (408) 222-4895
ssenthgirB
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11/27/01rev.4
www.supertex.com
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