HV862 Datasheet, PDF (1/7 Pages) Supertex, Inc – Dimmable, Low Noise, Dual EL Lamp Driver

HV862
Dimmable, Low Noise, Dual EL Lamp Driver
Features
► Adjustable output regulation for dimming
► Lamp fade-in/fade-out capability
► Low audible noise
► 180V_PP output voltage for higher brightness
► 1.5V enable input logic high
► Single cell lithium ion compatible
► One miniature inductor to power both lamps
► Separately adjustable lamp and converter frequencies
► Split supply capability
► 16-Lead QFN package
Applications
► Dual display cellular phones
► Keypad and LCD backlighting
► PDAs
► Handheld wireless communication products
► Global Positioning Systems (GPS)
The device uses a single inductor and a minimum number of
passive components. Using the internal reference voltage,
the regulated output voltage is at a nominal value of 90V.
The EL Lamps will therefore see ±90V. The two EL Lamps
can be turned ON and OFF using two CMOS logic inputs,
EN1 and EN2. The driver is disabled when both EN1 and
EN2 are at logic low.
The HV862 has two internal oscillators, a switching MOSFET,
and two high voltage EL Lamp driver H-bridges. Each driver
has its own half bridge common output, COM1 and COM2,
which significantly minimizes the DC offset seen by the EL
Lamp. 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 the R_EL-osc pin and the
V_DD pin. An external inductor is connected between the L_X
and V pins or V for split supply applications. Depending
DD
IN
upon the EL Lamp sizes, a 1.0nF to 10.0nF capacitor is
connected between the C_S and ground.
General Description
The Supertex HV862 is a low noise, dimmable, high
voltage, dual EL Lamp driver designed for driving two
electroluminescent (EL) Lamps with a combined area of 5.0
square inches. The input supply voltage range is from 2.5V
to 4.5V. Enable input logic high can go as low as 1.5V, which
allows logic interface operating from typical 1.8V supplies.
The device is designed to minimize audible noise emitted by
the EL Lamps.
As the switching MOSFET charges the external inductor
and discharges it into the capacitor at C_S, the voltage at
C will start to increase. Once the voltage at C reaches a
S
S
nominal value of 90V, the switching MOSFET is turned OFF
to conserve power.
EL Lamp dimming can be accomplished by applying a PWM
logic signal to the PWM pin. The EL Lamp brightness will be
proportional to the PWM duty cycle. The HV862 can also
slowly turn the EL Lamp ON/OFF giving a fade ON/OFF
appearance.
Typical Application Circuit
V_IN = 3.2V to 4.2V
4.7µF
100µH Coilcraft
LPS4012
1N4148
3.3MΩ
V_DD = 3.0V
0.1µF
Input Logic Control:
ON = 1.5V to V_DD
OFF = 0V to 0.2V
15 14 7
8
V_REG V_OUT L_X
3
2.0MΩ ₁
V_DD
R_EL-osc
2 R_SW-osc
825kΩ
4
EN1
5 _EN2
V_REF PWM
16
13
2.2µF
C_S
12
EL1
11
COM1
EL2 ⁹
COM2 ¹⁰
GND
6
HV862K7-G
3.3nF
100V NPO
EL1
EL2