© 2000 Calirornia Micro Devices Corp. All rights reserved.

12/5/2000

215 Topaz Street, Milpitas, California 95035

Tel: (408) 263-3214

Fax: (408) 263-7846

www.calmicro.com

CALIFORNIA MICRO DEVICES

CMPWR300

3

Interface Signals

V

present. If this connection is made within a few inches of

the main input filter, a bypass capacitor may not be necessary.

Otherwise a bypass filter capacitor in the range of 1µF to

10µF will ensure adequate filtering.

The voltage level on V

voltage to determine which power source is to be selected.

In order to prevent regulator dropout from occurring, the

threshold has been programmed to ensure V

prior to dropout, which prevents loss of output regulation

when switching between V

is set to 4.2V. Once V

voltage is immediately derived from the auxiliary power

source. To prevent chatter during this transition, the threshold

has a built-in hysteresis of 300mV which results in only V

CC

being selected once the voltage level exceeds 4.50V

(typically).

V

priority when V

remain enabled until such time that V

disable threshold level (4.2V typically). If the V

is made within a few inches of the main input filter, a bypass

capacitor may not be necessary. Otherwise a bypass filter

capacitor in the range of 1µF to 10µF will ensure adequate

filtering.

V

is only used when neither the V

these conditions an internal switch is enabled and provides

a very low impedance connection directly between V

OUT

and V

V

regulator or via the low impedance auxiliary switch. This

output requires a capacitance of 10µF to ensure regulator

stability and minimize the peak output disturbance during

power supply changeover.

GND provides the reference for all voltages.

S

L

A

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I

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C

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