SABRE-LL-I datasheet(42/141 Pages) STMICROELECTRONICS

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Switching regulator controller

SABRE-LL-I

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Switching regulator controller

13.1

Overview

This circuit controls an external FET to implement a switching buck regulator using a non

linear pulse skipping control with internally generated PWM signal.

The output voltage will be externally set by a divider network connected on feedback pin. To

reduce as much as possible the regulation voltage error S.A.B.Re has the possibility to

switch between four regulator feedback voltage references (and, as a consequence, four

under-voltage thresholds) using serial interface. The feedback reference voltage is selected

by writing the SelFBRef bits in the SwCtrCfg register according to the following table.

Adjustable feedback voltages can be changed using a metal layer change in order to adapt

it to customer system.

This regulator is switched off when S.A.B.Re is powered up for the first time and can be

enabled using S.A.B.Re’s SPI interface.

Here after are summarized the main features of the regulator:

–

Soft start circuitry to limit inrush current flow from primary supply.

–

Changeable feedback reference voltage

–

Internally generated PWM (250kHz switching frequency).

–

Nonlinear pulse skipping control.

–

Protected against load short circuit.

–

Cycle by cycle current limiting using internal current sensor.

–

Under voltage signal (both continuous and latched) accessible through SPI.

Table 22.

Switching regulator controller PWM specification

SwCtrCfg register

Reference voltage (VFBREF)

Unit

Comments

SelFBref[1]

SelFBref[0]

Min

Typ

Max

0.776

0.8

0.824

Default state

0.970

1.030

2.425

2.5

2.575

2.910

3.09

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