HV859 Datasheet, PDF (1/6 Pages) Supertex, Inc – High Voltage EL Lamp Driver for Low Noise Applications

Supertex inc.
HV859
Initial Release
High Voltage EL Lamp Driver for Low Noise Applications
Features
Patented audible noise reduction
Patented lamp aging compensation
210 V_PP output voltage for higher brightness
Patented output timing for high efficiency
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
Applications
LCD backlighting
Mobile Cellular Phone keypads
PDAs
Handheld wireless communication products
Global Positioning Systems (GPS)
Typical Application Circuit
ON = V_DD ^Enable
OFF = 0V
+
C_DD
R_SW
V_DD
-
R_EL
+
C_IN
V_IN
-
General Description
The Supertex HV859 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 a single inductor and a minimum number of
passive components. The nominal regulated output voltage
that is applied to the EL lamp is ±105V. The chip can be
enabled/disabled by connecting the resistor on R_SW-OSC to V_DD/
ground.
The HV859 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 R_SW-OSC pin and the supply pin V_DD. The EL lamp
driver frequency is set by an external resistor connected
between R_EL-OSC pin and the V_DD pin. An external inductor is
connected between the L_X and V_DD pins or V_IN for split supply
applications. A 0.003-0.1µF capacitor is connected between
C_S and ground. The EL lamp is connected between V_A and
V_B.
The switching MOSFET charges the external inductor and
discharges it into the capacitor at C_S. The voltage at C_S will start
to increase. Once the voltage at C_S reaches a nominal value
of 105V, the switching MOSFET is turned OFF to conserve
power. The outputs V_A and V_B are configured as an H bridge
and are switching in opposite states to achieve ±105V across
the EL lamp.
1 V_DD
2 R_SW-osc
V_A 8
V_{B 7}
3 R_EL-osc
C_S 6
4 GND
L_X 5
HV859MG/
HV859K7
R_SER
D
L_X
EL Lamp
C_S
NR040306
· · · · ^{Supertex inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: [phone] FAX: [phone] www.supertex.com}
1