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CMPWR150SF

500mA/3.3V SmartOR™ Power Regulator

ON Semiconductor 

CMPWR150

Typical Transient Characteristics

The transient characterization test set-up shown below includes the effective source impedance of the VCC

supply (RS). This 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 VCC selection and

deselection.

Both the rise and fall times during VCC power-up/down sequencing were controlled at a 20 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 VAUX to VCC and vice versa. In

addition to the normal load current, there may also be an in-rush current for charging/discharging the load

capacitor. The total current pulse being applied to either VAUX or VCC is equal to the sum of the DC load and the

corresponding in-rush current. Transient currents in excess of 1.0 amps can readily occur for brief intervals

when either supply commences to power the load.

The oscilloscope traces of VCC power-up/down show the full bandwidth response at the VCC and VOUT pins under

full load (500mA) conditions.

See Application Note AP-211 for more information.

VCC Power-up Cold Start. Figure 5 shows the output response during an initial VCC power-up with VAUX not

present. When VCC reaches the select threshold, the regulator turns on. The uncharged output capacitor

causes maximum in-rush current to flow, resulting in a large voltage disturbance at the VCC pin of about 230mV.

The built-in hysteresis of 250mV ensures the regulator remains enabled throughout the transient.

Prior to VCC reaching an acceptable logic supply level (2V), a disturbance on the Drive pin can be observed.

PowerUpCold.bmp

Figure 5. VCC Power-up Cold Start

Rev. 3 | Page 8 of 15 | www.onsemi.com

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