HV859 データシートの表示（PDF） - Supertex Inc

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HV859

High Voltage EL Lamp Driver for Low Noise Applications

Supertex Inc 

HV859

External Component Description

External Component Selection Guide Line

Diode

Fast reverse recovery diode, BAS21 diode or equivalent.

CS Capacitor

0.003µF to 0.1µF, 200V capacitor to GND is used to store the energy transferred from the

inductor.

REL Resistor

The EL lamp frequency is controlled via an external REL resistor connected between REL-Osc and

VDD of the device. The lamp frequency increases as REL decreases. As the EL lamp frequency

increases, the amount of current drawn from the battery will increase and the output voltage VCS

will decrease. The color of the EL lamp is dependent upon its frequency.

A 2MΩ resistor would provide lamp frequency of 175 to 235Hz. Decreasing the REL resistor by a

factor of 2 will increase the lamp frequency by a factor of 2.

RSW Resistor

LX Inductor

The switching frequency of the converter is controlled via an external resistor, RSW between

RSW-Osc and VDD of the device. The switching frequency increases as RSW decreases. With

a given inductor, as the switching frequency increases, the amount of current drawn from the

battery will decrease and the output voltage, VCS, will also decrease.

The inductor LX is used to boost the low input voltage by inductive flyback. When the internal

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 CS. The energy stored in the

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

the inductor value decreases, the switching frequency of the inductor (controlled by RSW) should

be increased to avoid saturation.

Lamp

A220µH 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 RSW

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, (VIN x IIN), will also increase. If the input power is

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.

Doc.# DSFP-HV859

C073013

Supertex inc.

6

www.supertex.com

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