CALIFORNIA MICRO DEVICES

©2000 California 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

CMPWR300

6

The transient characterization test setup shown below includes

the effective source impedance of the V

was measured to be approximately 0.2Ω. It is recommended

that this effective source impedance be no greater than 0.25Ω

to ensure precise switching is maintained during V

and deselection.

Both the rise and fall times during V

sequencing were controlled to be around 10 millisecond

duration. This is considered to represent worst case conditions

for most application circuits.

A maximum rated load current of 500mA was used during

characterization, unless specified otherwise.

During a selection or deselection transition the DC load current

is switching from V

V

be an in-rush current for charging/discharging the load

capacitor. The total current pulse being applied to either

V

corresponding in-rush current. Transient currents in excess

of one amp can readily occur for brief intervals when either

supply commences to power the load.

The oscilloscope traces of V

bandwidth response at the V

(500mA) conditions.

See Application note AP-211 for more details.

Cold Start and Full Power Down (Fig 2.1 to 2.6)

Cold start power up and power down from V

V

with no disturbance. As soon as the V

reaches about 2V, V

V

drops below 3.8V.

V

Power transitions between the main V

the auxiliary sources under 375mA load. The transition

between V

on V

Transitions between V

about 120mV on V

experiences 100mV disturbance.

This is due to the in-rush current during the power switching.

The built-in hysteresis of 300mV ensures the regulator

remains turned on throughout the transient.

Load and Line Transient Response (Fig 2.13 to 2.16)

The load transient response shows a 5mA to 500mA step

load with minimal disturbance on V

transient overshoot of 80mV occurs and the output settles

to its final voltage within a few microseconds. The dc voltage

disturbance on the output is approximately 25mV, which

demonstrates the regulator output impedance of 50mW.

The line step response shows a small disturbance of 25mV

on the output when V

falling from 5.5V to 4.5V, the output is almost unchanged

Typical Transient Characteristics