HV843
Initial Release
Low Noise Dual EL Lamp Driver
Features
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Low audible noise
Independent input control for lamp selection
180V
pp
output voltage
Split supply capability
Patented output timing
One miniature inductor to power both lamps
Low shutdown current
Wide input voltage range 2.0V to 5.8V
Output voltage regulation
No SCR output
Available in DFN/MLP - 10 package
General Description
The Supertex HV843 is a low noise, high voltage driver designed
for driving two EL lamps with a combined area of 3.5 square
inches. The input supply voltage range is from 2.0V to 5.8V.
The device is designed to reduce the amount of audible noise
emitted by the lamp. This device uses a single inductor and a
minimum number of passive components to drive two EL lamps.
The nominal regulated output voltage of ±90V is applied to the
EL lamps. The two EL lamps can be turned ON and OFF by the
two logic input control pins, C
1
and C
2
. The device is disabled
when both C
1
and C
2
(pins 1 and 4) are at logic low.
The HV843 has an internal oscillator, a switching MOSFET, and
two high voltage EL lamp drivers. Each driver has its own half
bridge common output (COM1 and COM2) connected to a single
pin called COM which minimizes the DC offset seen by the EL
lamp. An external resistor connected between the R
SW-OSC
pin and
the voltage supply pin, V
DD
, sets the frequency for the switching
MOSFET. The EL lamp driver frequency is set by dividing the
MOSFET switching frequency by 512. An external inductor is
connected between the L
X
and the V
DD
pins. Depending on the EL
lamp size, a 1.0 to 10.0nF, 100V capacitor is connected between
C
S
and Ground. The switching MOSFET charges the external
inductor and discharges it into the capacitor at C
S
. The voltage
at C
S
increases. Once the voltage at C
S
reaches a nominal value
of 90V, the switching MOSFET is turned OFF to conserve power.
Applications
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Dual display cellular phones
Keypad and LCD backlighting
Portable instrumentation
Dual segment lamps
Hand held wireless communication devices
Typical Application Circuit
3.3MΩ
1.0µF
EL Lamp 1
1
2
1.5V
1.5V
0
0
C
1
V
DD
R
SW-OSC
EL
1
EL
2
Com
C
S
L
X
10
9
8
7
6
3.3MΩ
1.0µF
EL Lamp 2
+
V
DD
C
DD
0.1µF
845kΩ
3
4
C
2
5
-
C
IN
4.7µF
D
GND
HV843K7-G
+
V
IN
L
X
330µH
C
S
3.3nF, 100V
-
1
SUPERTEX [ Supertex, Inc ]
