MIC4832 datasheet(10/22 Pages) MICROCHIP

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MIC4832

DS20006163B-page 10

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2019 - 2022 Microchip Technology Inc.

5.0

APPLICATION INFORMATION

5.1

Inductor

A 220 µH Murata (LQH4C221K04) inductor is

recommended for most applications. Generally,

inductors with smaller values can handle more current.

Lowering the inductance allows the boost regulator to

draw more input current to deliver more energy every

cycle. As a result, a lower value inductor may be used

to drive larger panels or make the current panel

brighter.

However, caution is required as using a low-value

inductor with a low switching frequency may result in

voltages exceeding the absolute maximum rating of

the switch node and/or the CS pin.

If the application uses a low-input voltage (1.8V to 3V),

a lower value inductor, such as 100 µH, may be used in

order to drive the EL lamp at max brightness without

issue.

5.2

Diode

The diode must have a high-reverse voltage (150V),

because the output voltage at the CS pin can reach up

to 130V. A fast-switching diode with lower forward

voltage and higher reverse voltage (150V), such as

BAV20WS/BAS20W, can be used to enhance

efficiency.

5.3

Output Capacitor

Low-ESR capacitors should be used at the regulated

boost output (CS pin) of the MIC4832 to minimize the

switching output ripple voltage. The larger the output

capacitance, the lower the output ripple at the CS pin.

The reduced output ripple at the CS pin, along with a

low-ESR capacitor, improves the efficiency of the

MIC4832 circuit.

Selection of the capacitor value will depend upon the

peak inductor current, inductor size, and the load. The

MIC4832 is designed for use with an output

capacitance as low as 2.2 nF. For minimum audible

noise, the use of a C0G/NPO dielectric output capacitor

is recommended.

TDK and AVX offer C0G/NPO dielectric capacitors in

capacitances up to 2.7 nF at 200V to 250V rating in

0805 size. If output ripple is a concern, a 0.01 µF/200V

X7R output capacitor is recommended.

5.4

EL Lamp Terminals (VA, VB)

An EL lamp is connected from VA to VB as the load.

The high voltage alternated across VA and VB by the

H-bridge cycles generate luminance.

The voltage at VA and VB should not exceed the

voltage at VCS by more than 3V. This situation may

become present when noisy enable signals such as

those often generated by mechanical switches are

applied to the driver’s inputs.

To prevent overvoltage at VA and VB, 10 kΩ resistors

may be placed in series from VA to the EL panel and

from VB to the EL panel. An alternative to the use of

10 kΩ resistors is to apply a diode from the CS pin to

VA and VB, where the cathode of the diode is on the CS

side and the anode is on the VA and VB side,

respectively.

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