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HV857MG

High Voltage EL Lamp Driver for Low Noise Applications

Supertex Inc 

LX Inductor Selection:

Different inductor values and/or from different manufacturers

can be used in place of what is shown. However, the circuit will

need to be reoptimized by changing the RSW-OSC value. Smaller

RSW-OSC value needs to be used for inductors with lower series

resistance. Lower amount of current will be drawn when using

larger value inductors. But, for the same RSW-OSC value, a lower

amount of energy will be transferred due to the higher series

resistance of a larger value inductor. Hence, when larger value

inductors with higher series resistance are used, the RSW-OSC

value needs to be increased. It is very important to make a note

of the saturation current of the inductor. If the saturation current

of the inductor is lower than what the circuit/application requires,

the inductor and/or IC will be damaged.

HV857 Application Note

CS Capacitor Selection:

Different CS Capacitor types and value can be used in place of

what is shown in circuits 1 to 9. However, the use of a different

CS Capacitor type will generate audible noise due to the piezo

electric effect of materials used for their structure (such as X7R

and 5YU capacitors).

A different value capacitor can be used. A larger value CS

Capacitor (10nF) is recommended to be used for larger EL lamps

and/or larger input voltage range. A smaller value CS Capacitor

can be used as long as the over all efficiency of the circuit is not

decreased. When using a smaller value CS Capacitor, the circuit

will need to be reoptimized by using a smaller RSW-OSC value.

©2001 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.

14

11/27/01AppNote.rev.3

1235 Bordeaux Drive, Sunnyvale, CA 94089

TEL: (408) 744-0100 • FAX: (408) 222-4895

www.supertex.com

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