HV857
HV857
High Voltage EL Lamp Driver for
Low Noise Applications
Features
General Description
❏ Patent pending audible noise reduction
❏ Patent pending lamp aging compensation
❏ 190VPP output voltage for higher brightness
❏ Patented output timing for high efficiency
❏ Single cell lithium ion compatible
❏ 150nA shutdown current
The Supertex HV857 is a high voltage driver designed for driving
Electroluminescent (EL) lamps of up to 5 square inches. The
input supply voltage range is from 1.8V to 5.0V. The device uses
asingleinductorandaminimumnumberofpassivecomponents.
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 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 be-
tween REL-osc pin and the 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.
❏ Wide input voltage range 1.8V to 5.0V
❏ Separately adjustable lamp and converter frequencies
❏ Output voltage regulation
❏ Split supply capability
Applications
❏ LCD backlighting
❏ Mobile cellular phones
❏ PDAs
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
switchinginoppositestatestoachieve ±95VacrosstheELlamp.
❏ Handheld wireless communication products
❏ Global Positioning Systems (GPS)
Typical Application
Enable Signal
ON=VDD
OFF=0
Regulated Voltage=VDD
VDD
1
VA
8
EL Lamp
RSW-osc
VB
CS
LX
7
6
5
2
3
4
REL-osc
Gnd
V
=VIN
DD
CIN
LX
HV857MG
CS
11/14/01
Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products liability
indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be defective due to
workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the
Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer page on the Supertex website.
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