Supertex inc.
Low Noise Dual EL Lamp Driver
Features
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Low audible noise
Independent input control for lamp selection
160V
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 MLP/DFN-10 package
HV835
Initial Release
General Description
The Supertex HV835 is a 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 num-
ber of passive components to drive two EL lamps. The nominal
regulated output voltage of ±80V 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 HV835 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 80V, 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
Handheld wireless communication devices
Typical Application Circuit
3.3MΩ
1.0µF
EL Lamp 1
1
2
10
9
8
7
6
1.5V
1.5V
0
845kΩ
0
C
1
V
DD
R
SW-OSC
C
2
GND
EL
1
EL
2
Com
C
S
L
X
1.0µF
3.3MΩ
+
V
DD
C
DD
0.1µF
3
4
EL Lamp 2
-
5
D
HV835K7-G
+
V
IN
C
IN
4.7µF
L
X
330µH
C
S
3.3nF, 100V
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Supertex inc.
·
1235 Bordeaux Drive, Sunnyvale, CA 94089
·
Tel: (408) 222-8888
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FAX: (408) 222-4895
·
www.supertex.com
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