HV857L_13 Datasheet, PDF (1/8 Pages) Supertex, Inc – Low Noise, High Voltage EL Lamp Driver IC

Supertex inc.
HV857L
Low Noise, High Voltage
EL Lamp Driver IC
Features
►►Audible noise reduction
►►190 V_PP output voltage for higher brightness
►►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 and 8-Lead MSOP-
packages
Applications
►► Mobile cellular phones
►► Keypad backlighting
►► LCD backlighting
►► PDAs
►► Handheld wireless communication products
►► Global Positioning Systems (GPS)
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.
Typical Application Circuit
ON = V_DD
OFF = 0
+
_^VDD
+
_^VIN
Enable Signal
1 _VDD
8
VA
C_DD
R_SW
HV857L
2 _RSW-Osc
7
VB
3 _REL-Osc
C_IN
R_EL
4 _GND
6
CS
5
LX
EL Lamp
D
L_X
C_S
Doc.# DSFP-HV857L
A062013
Supertex inc.
www.supertex.com