HV823LG Ver la hoja de datos (PDF) - Supertex Inc

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componentes Descripción

Fabricante

HV823LG

High Voltage EL Lamp Driver IC

Supertex Inc 

HV823

External Component Description

External Component

Diode

CS Capacitor

REL-Osc

Selection Guide Line

Fast reverse recovery diode, 1N4148 or equivalent.

0.01µF to 0.1µF, 100V capacitor to GND is used to store the energy transferred from the induc-

tor.

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

and VDD pins 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.

RSW-Osc

CSW Capacitor

LX Inductor

A 2.0MΩ resistor would provide lamp frequency of 330 to 450Hz. Decreasing the REL-Osc by a fac-

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

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

RSW-Osc and VDD pins 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.

A 1.0nF capacitor is recommended on RSW-Osc to GND when a 0.01μF CS capacitor is used.

This capacitor is used to shunt any switching noise that may couple into the RSW-OSC pin.

The CSW capacitor may also be needed when driving large EL lamp due to increase in switching

noise. A CSW larger than 1.0nF is not recommended.

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 capaci-

tor 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

560µH Murata inductors with 14.5Ω series DC resistance is typically recommended. For induc-

tors with the same inductance value but with lower series DC resistance, lower RSW 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 (400mW), 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: 408-222-8888 ● www.supertex.com

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