HV859MG-G Supertex, HV859MG-G Datasheet - Page 6

• Manufacturer Part Number: HV859MG-G
• Description: Display Drivers High Voltage Low Noise EL Lamp
• Manufacturer: Supertex

Specifications of HV859MG-G

• Mounting Style: SMD/SMT
• Package / Case: MSOP-8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

HV859
External Component Description
External Component
Selection Guide Line
Diode
Fast reverse recovery diode, BAS21 diode or equivalent.
0.003µF to 0.1µF, 200V capacitor to GND is used to store the energy transferred from the
C
Capacitor
inductor.
S
The EL lamp frequency is controlled via an external R
resistor connected between REL-Osc and
EL
VDD of the device. The lamp frequency increases as R
decreases. As the EL lamp frequency
EL
increases, the amount of current drawn from the battery will increase and the output voltage V
CS
R
Resistor
will decrease. The color of the EL lamp is dependent upon its frequency.
EL
A 2MΩ resistor would provide lamp frequency of 175 to 235Hz. Decreasing the R
resistor by a
EL
factor of 2 will increase the lamp frequency by a factor of 2.
The switching frequency of the converter is controlled via an external resistor, R
between
SW
RSW-Osc and VDD of the device. The switching frequency increases as R
decreases. With
R
Resistor
SW
a given inductor, as the switching frequency increases, the amount of current drawn from the
SW
battery will decrease and the output voltage, V
, will also decrease.
CS
The inductor L
is used to boost the low input voltage by inductive flyback. When the internal
X
switch is on, the inductor is being charged. When the internal switch is off, the charge stored
in the inductor will be transferred to the high voltage capacitor C
. The energy stored in the
S
capacitor is connected to the internal H-bridge, and therefore to the EL lamp. In general, smaller
value inductors, which can handle more current, are more suitable to drive larger size lamps. As
L
Inductor
the inductor value decreases, the switching frequency of the inductor (controlled by R
) should
X
SW
be increased to avoid saturation.
A 220µH Murata (LQH32CN221) inductor with 8.4Ω series DC resistance is typically recommended.
For inductors with the same inductance value, but with lower series DC resistance, lower R
SW
resistor value is needed to prevent high current draw and inductor saturation.
As the EL lamp size increases, more current will be drawn from the battery to maintain high
voltage across the EL lamp. The input power, (V
x I
), will also increase. If the input power is
Lamp
IN
IN
greater than the power dissipation of the package, an external resistor in series with one side of
the lamp is recommended to help reduce the package power dissipation.
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
Tel: [phone]
www.supertex.com
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