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HV857_13 Datasheet, PDF (1/9 Pages) Supertex, Inc – Low Noise, High Voltage EL Lamp Driver IC | |||
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Supertex inc.
HV857
Low Noise, High Voltage
EL Lamp Driver IC
Features
âºâºPatented audible noise reduction
âºâºPatented lamp aging compensation
âºâº190 VPP output voltage for higher brightness
âºâºPatented output timing for high efficiency
âºâºSingle cell lithium ion compatible
âºâº150nA shutdown current
âºâºWide input voltage range 1.8 to 5.0V
âºâºSeparately adjustable lamp and converter
frequencies
âºâºOutput voltage regulation
âºâºSplit supply capability
âºâºAvailable in 8-Lead MSOP and DFN packages
Applications
âºâº LCD backlighting
âºâº Mobile Cellular Phone
âºâº PDAs
âºâº Handheld wireless communication products
âºâº Global Positioning Systems (GPS)
General Description
The Supertex HV857 is a high voltage driver designed for driving
Electroluminescent (EL) lamps of up to 5.0 square inches. The
input supply voltage range is from 1.8 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/GND.
The HV857 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 REL-
Osc pin and VDD pin. 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 VA and VB.
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 = VDD
Enable Signal
OFF = 0
+
_ VDD
CDD
1 VDD
VA 8
RSW
HV857
2 RSW-Osc
VB 7
EL Lamp
+
_ VIN
3 REL-Osc
CS 6
REL
4 GND
LX 5
D
CIN
LX
CS
Doc.# DSFP-HV857
A062013
Supertex inc.
www.supertex.com
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