900844 datasheet(64/118 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

900844

FUNCTIONAL DEVICE OPERATION

POWER SUPPLIES

The output current is measured internally, digitized by the ADC, and stored in a register for the processor to access.

The peak current is sensed internally for over-current protection purposes. If an over-current condition is detected, the

regulator will limit the current through cycle by cycle operation and alert the system through the V21FAULT signal, which will in

turn assert the VRFAULT Interrupt signal.

Figure 30. V21 Detailed Internal Block Diagram

Main Features

• Uses the VPWR rail as its power supply

• It is used as a pre-regulator to many LDO rails, for enhanced efficiency and reduced thermal dissipation.

• Uses Integrated MOSFETs

•4.0 MHz switching frequency

• High efficiency operating modes depending on load conditions

• Output can be discharged through the low side switch.

• Peak current sensing with over-current protection

• Uses internal compensation

• Gate drive circuits are supplied directly from VPWR

Efficiency Curves

Figure 31 efficiency curves are calculated under PWM mode, based on the recommended external component values and

typical output voltage of 2.1 V. 3.0 V

≤ VPW ≤ 4.4 V.

Driver

Controller

VREF

Internal

Compensation

PVIN 21

SW21

FB21

ISENSE5

VPWR

CO21

CIN 21

L21

SPI

Interface

PGND21

V21

CTLV21

AOACCTLV21

V21FAULT

900844 데이터시트(PDF) 64 Page - Freescale Semiconductor, Inc

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