900844 datasheet(66/118 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

900844

FUNCTIONAL DEVICE OPERATION

POWER SUPPLIES

V21 Status/Control Registers and Bits Description

Reference the register map for read/write conditions and default state for each of these registers.

V15

This is a 4.0 MHz fully integrated 2-switch synchronous Buck PWM voltage-mode control DC/DC regulator.

The switcher can operate in different modes depending on the load conditions. These modes can be set through the SPI and

include a PFM mode, an Automatic Pulse Skipping mode, and a PWM mode. The above selection is optimized to maximum

battery life based on load conditions.

V15 will be discharged every time the regulator is shutting down.

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 V15FAULT signal, which will in

turn assert the VRFAULT Interrupt signal.

Figure 32. V15 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. It also supplies power

to rails in the Platform controller hub

• Uses Integrated MOSFETs

Table 28. V21 Status/Control Registers Structure and Bits Description

Name

Bits

Description

V21CNT (ADDR 0x38 - R/W - Default value: 0x07)

CTLV21

2:0

V21 State Control

x0 = Reserved

x1 = Reserved

x2 = Reserved

x3 = Reserved

x4 = OFF

x5 = PFM

x6 = Automatic Pulse Skipping

x7 = PWM

AOACCTLV21 5:3

V21 State Control during AOAC Exit (when EXITSTBY pin is asserted). These bits will be initialized by the system SPI

controller after power up

X0 = Do not copy

x1 = Do not copy

x2 = Do not copy

x3 = Do not copy

x4 = OFF

x5 = PFM

x6 = Automatic Pulse Skipping

x7 = PWM

Reserved

7:6

Reserved

Driver

Controller

VREF

Internal

Compensation

PVIN 15

SW15

FB15

ISENSE5

VPWR

CO15

CIN 15

L15

SPI

Interface

PGND15

V15

CTLV15

AOACCTLV15

V15FAULT

SELV15

900844 Datasheet(PDF) 66 Page - Freescale Semiconductor, Inc

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