HV841 Datasheet, PDF (1/7 Pages) Supertex, Inc – High Voltage Dual EL Lamp Driver

Supertex inc.
HV841
Initial Release
High Voltage Dual EL Lamp Driver
Features
Independent input control for lamp selection
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 small packages (10-lead MSOP and
10-lead DFN/MLP)
Applications
Mobile cellular phones, dual display
Keypad and LCD backlighting
Portable instrumentation
Dual segment lamps
Hand held wireless communication devices
General Description
The Supertex HV841 is a 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
±100V is applied to the EL lamps. The chip can be enabled/ disabled
by connecting C₁ and C₂ (pins 1 and 4) to V_EN/ Ground.
The HV841 has an internal oscillator, a switching MOSFET, and two
high voltage EL lamp drivers. An external resistor connected between
the R_SW-OSC and the voltage supply pin V_DD sets the frequency for the
switching MOSFET. The EL lamp driver frequency is set by dividing
the MOSFET switching frequency by 128. An external inductor is
connected between the L_X and the V_DD pins. Depending on the EL
lamp size, a 1.0 to 10.0nF, 200V capacitor is connected between C_S
and Ground. The two EL lamps are connected between EL₁ to Com
and EL₂ to Com.
The switching MOSFET charges the external inductor and discharges
it into the capacitor at C_S. The voltage at C_S increases. Once the
voltage at C_S reaches a nominal value of 100V, the switching
MOSFET is turned off to conserve power. The outputs EL to Com
1
and EL₂ to Com are configured as H bridges and switch in opposite
states to achieve 200V across the EL lamp.
Typical Application Circuit
V_EN = ON
V_EN = ON ^{0 = OFF}
0 = OFF
1 _C1
EL₁ ¹⁰
+
V_DD
-
C_DD
2
R_SW-OSC
3
V_DD
R_SW-OSC
EL₂ ⁹
Com 8
4 C2
5 _GND
C_S 7
L_X 6
+
V_IN
HV841MG-G/
HV841K6-G
C_IN
-
EL Lamp 1¹
D
~ ^LX
EL Lamp 2¹
C_S
1 The bigger sized lamp should be tied to EL1 and the smaller
sized lamp to EL2 terminals (pins 10 and 9 respectively)
NR033106
· · · · ^{Supertex inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: [phone] FAX: [phone] www.supertex.com}
1