Supertex inc.
Tri-EL Lamp Driver IC
Features
Tri-EL lamp driver with common terminal
Independent brightness control for all 3 lamps
1.8V to 6.5V Operating Supply Voltage
Output voltage regulation
Two-pin serial data communication for control
Linear brightness control with seven steps at constant
efficiency
128kHz Fixed Switching Frequency
Split supply capability
Patented high efficiency EL lamp driver
Single miniature inductor drives all 3 lamps
Only 4 external components
Burst mode power converter for best efficiency
CMOS compatible serial interface with noise rejection
150nA max. leakage current when disabled
Power-on reset causes all outputs to be off when first
powered up
Small 10-pin MSOP package
10-pin DFN/MLP package (0.8mm thickness)
HV858
General Description
The Supertex HV858 is a high voltage triple EL lamp driver
designed for driving combined EL lamps of up to 3.0 in
2
(1.0 in
2
each). The input supply voltage range is from 1.8V
to 6.5V. The device is designed such that the input voltage
to the inductor can be different from the input voltage to the
device (split supply). 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
±95V. The HV858 has two internal oscillators, one for the
internal switching MOSFET, and the other for the high voltage
EL lamp driver. The EL lamp frequency is fixed internally at
500Hz. The power converter oscillator runs 256 times faster
than the EL lamp driver at 128kHz.
An external inductor is connected between the L
X
and V
DD
pins (or between the L
X
pin and separate voltage source in
the case of a split supply application). A 0.002-0.01µF, 100V
capacitor is connected between the C
s
pin and ground.
The switching MOSFET charges the external inductor and
discharges it into the capacitor at the C
s
pin. The voltage at
C
s
will start to increase. Once the voltage at C
s
reaches a
nominal value of 95V, the switching MOSFET is turned OFF
to conserve power.
One side of the 3 EL lamps is connected to the Com pin of
HV858 and the other side to the EL1, EL2, and EL3 pins of the
HV858. Each EL lamp output may be independently controlled
to have one of the 7 brightness levels or can be completely
turned OFF by a 10-bit serial data input register. The 10-bit
control code has 3 bits to control the brightness level of each
EL Lamp and one bit to optionally control the power converter.
The 3-bit binary brightness control code controls the number
of 500Hz cycles (from 0 to 7) in a group of 7 cycles.
L
X
Applications
Mulit-segment, variable displays
Cell phone keypads and displays
MP3 players
Watches
Typical Application Circuit
D
V
IN
+
C
IN
-
C
S
1 L
X
2 GND
C
S
10
Com 9
EL3 8
EL2 7
EL1 6
EL Lamp 3
EL Lamp 2
EL Lamp 1
V
DD
+
C
DD
3 V
DD
4 SDI
5 SCK
-
Serial Data in
Clock
HV858
A011706
Supertex inc.
A011706
·
1235 Bordeaux Drive, Sunnyvale, CA 94089
·
Tel: (408) 222-8888
·
FAX: (408) 222-4895
·
www.supertex.com
1
SUPERTEX [ Supertex, Inc ]
