HV857LMGG Supertex, HV857LMGG Datasheet
HV857LMGG
Manufacturer Part Number
HV857LMGG
Description
MSOP8
Manufacturer
Supertex
Specifications of HV857LMGG
Date_code
09+
Features
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Applications
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Typical Application Circuit
Audible noise reduction
190 V
Single cell lithium ion compatible
150nA shutdown current
Wide input voltage range 1.8V to 5.0V
Separately adjustable lamp and converter
frequencies
Output voltage regulation
Split supply capability
Available in 8-Lead DFN (K7) and 8-Lead MSOP
(MG) packages
Mobile cellular phones
Keypad backlighting
LCD backlighting
PDAs
Handheld wireless communication products
Global Positioning Systems (GPS)
V
PP
V
DD
IN
output voltage for higher brightness
+
_
+
_
ON = V
OFF =
Low Noise, High Voltage EL Lamp Driver IC
0
DD
C
C
DD
IN
Enable Signal
R
R
SW
EL
1
2
3
4
GND
RSW-Osc
REL-Osc
VDD
HV857L
General Description
The Supertex HV857L is a low noise, high voltage driver
designed for driving Electroluminescent (EL) lamps of up to five
square inches. It is the low noise version of the EL lamp driver
HV857. The input supply voltage range is from 1.8V to 5.0V. 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 chip can be enabled/disabled by
connecting the resistor on RSW-Osc to VDD/ground.
The HV857L 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 RSW-Osc pin and the supply pin, VDD. The EL
lamp driver frequency is set by an external resistor connected
between the REL-Osc and VDD pins. An external inductor is
connected between the LX and VDD pins, or VIN for split supply
applications. A 0.003-0.1µF capacitor is connected between CS
and ground. The EL lamp is connected between the VA and VB
pins.
The switching MOSFET charges the external inductor and
discharges it into the capacitor at CS. The voltage at CS will
start to increase. Once the voltage at CS reaches a nominal
value of 95V, the switching MOSFET is turned OFF to conserve
power. The outputs VA and VB are configured as an H bridge,
and are switching in opposite states to achieve ±95V across the
EL lamp.
VA
VB
CS
LX
8
7
6
5
L
X
D
C
S
EL Lamp
HV857L
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