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HV845 Datasheet, PDF (1/6 Pages) Supertex, Inc – Low Noise Dual EL Lamp Driver
HV845
Initial Release
Low Noise Dual EL Lamp Driver
Features
► Low audible noise
► Independent input control for lamp selection
► 180VPP output voltage
► Split supply capability
► Patented output timing
► One miniature inductor to power both lamps
► Low shutdown current
► Wide input voltage range 2.0V to 5.8V
► Output voltage regulation
► No SCR output
► Available in 12-Lead QFN/MLP package
Applications
► Dual display cellular phones
► Keypad and LCD backlighting
► Portable instrumentation
► Dual segment lamps
► Hand held wireless communication devices
General Description
The Supertex HV845 is a low noise, high voltage driver
designed for driving two EL lamps with a combined area of 3.5
square inches. The input supply voltage range is from 2.0V to
5.8V. The device is designed to reduce the amount of audible
noise emitted by the lamp. This device uses a single inductor
and minimum number of passive components to drive two EL
lamps. The nominal regulated output voltage of ±90V is applied
to the EL lamps. The two EL lamps can be turned ON and OFF
by the two logic input control pins, C1 and C2. The device is
disabled when both C1 and C2 (pins 12 and 3) are at logic low.
The HV845 has an internal oscillator, a switching MOSFET, and
two high voltage EL lamp drivers. Each driver has its own half
bridge common output COM1 and COM2, which significantly
minimizes the DC offset seen by the EL lamp. An external
resistor connected between the RSW-OSC pin and the voltage
supply pin, VDD, sets the frequency for the switching MOSFET.
The EL lamp driver frequency is set by dividing the MOSFET
switching frequency by 512. An external inductor is connected
between the LX and the VDD pins. Depending on the EL lamp size,
a 1.0 to 10.0nF, 100V capacitor is connected between CS and
Ground. The switching MOSFET charges the external inductor
and discharges it into the capacitor at CS. The voltage at CS
increases. Once the voltage at CS reaches a nominal value of
90V, the switching MOSFET is turned OFF to conserve power.
Typical Application Circuit
330µH
+
VIN -
LX
CIN
4.7µF
+
VDD
-
CDD
0.1µF
1.5V
0
1.5V
0
845kΩ
5
1 VDD LX
6
10
CS EL1
2
RSW-OSC
12
C1
COM1 8
EL2 9
3 C2
7
GND COM2
4
HV845K7-G
D
1.0µF
1.0µF
3.3MΩ
CS
3.3nF, 100V
EL Lamp 1
3.3MΩ
EL Lamp 2
1
 ▷