HV831
High Voltage Dual EL Lamp Driver
Features
Independent input control for lamp selection
Split supply capability
Patented output timing
One miniature inductor to power both lamps
Low shutdown current
Wide input voltage range 2.0V to 5.0V
Output voltage regulation
No SCR output
Available in 10 - pin MSOP package
General Description
The Supertex HV831 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 5.0V. The device is designed to
reduce the amount of audible noise emitted by the lamp. This device
uses a single inductor and minimum number 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 HV831 has an internal oscillator, a switching MOSFET, and two
high voltage EL lamp drivers. An external resistor connected between
the R
SW-OSC
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 128. 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 two EL lamps are connected between EL
1
to Com
and EL
2
to Com.
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. The outputs EL
1
to Com and EL
2
to
Com are configured as H bridges and switch in opposite states to
achieve 160V across the EL lamp.
Applications
Mobile cellular phones, dual display
Keypad and LCD backlighting
Portable instrumentation
Dual segment lamps
Hand held wireless communication devices
Typical Application Circuit
V
DD
= ON
0 = OFF
V
DD
= ON
0 = OFF
1
EL Lamp 1
1
C
1
V
DD
EL
1
EL
2
10
9
8
7
6
+
V
DD
-
C
DD
R
SW-OSC
2
3
4
5
R
SW-OSC
Com
C2
GND
C
S
L
X
EL Lamp 2
1
D
HV831MG
V
IN
+
C
IN
-
~
L
X
C
S
1 The bigger sized lamp should be tied to EL1 and the smaller
sized lamp to EL2 terminals (pins 10 and 9 respectively)
A081005
1
SUPERTEX [ Supertex, Inc ]
