HV833
High Voltage EL Lamp Driver
Features
►
1.8V to 6.5V operating supply voltage
►
DC to AC conversion
►
Separately adjustable lamp and converter
frequency
►
Output voltage regulation
►
Enable/disable function
►
Patented output timing for high efficiency
►
<100nA shutdown current
►
Split supply capability
►
LCD backlighting
General Description
The Supertex HV833 is a high voltage driver designed for driving EL
lamps of up to 35nF (10-12in
2
). The input supply voltage range is
from 1.8V to 6.5V. The device uses a single inductor and a minimum
number of passive components. The nominal regulated output voltage
that is applied to the EL lamp is ±90V. The chip can be enabled/
disabled by connecting a resistor between the R
SW-Osc
pin and the
V
DD
/GND pins.
The HV833 has two internal oscillators, a switching MOSFET, and a
high voltage EL lamp driver. The frequency for the switching MOSFET
is set by an external resistor connected between the R
SW-Osc
pin and
the V
DD
supply pin. The EL lamp driver frequency is set by an external
resistor connected between the R
EL-Osc
pin and the V
DD
pin. An external
inductor is connected between the L
X
pin and V
DD
or V
IN
pin. A 0.003-
0.1µF capacitor is connected between the C
S
pin and the GND pin.
The EL lamp is connected between the V
A
pin and the V
B
pin.
The switching MOSFET charges the external inductor and discharges
it into the capacitor at C
S
. The voltage at C
S
will start to increase.
Once the voltage at C
S
reaches a nominal value of 90V, the switching
MOSFET is turned OFF to conserve power. The outputs V
A
and V
B
are configured as an H bridge and are switching in opposite states to
achieve 180V peak-to-peak across the EL lamp.
Applications
►
►
►
►
►
Portable Transceivers
Remote Control Units
Calculators
PDAs
Global Positioning Systems (GPS)
Typical Application Circuit
ON = V
DD
OFF = 0
V
DD
Enable Signal
1
2
3
4
V
DD
V
A
V
B
8
EL Lamp
7
6
R
SW-Osc
R
EL-Osc
GND
C
S
L
X
1N914
5
V
IN
+
_
HV833MG
L
X
C
S
100V
SUPERTEX [ Supertex, Inc ]
