7 Detailed Description

7.1 Overview

The TPS6291x low-noise, low-ripple synchronous buck converter is a fixed frequency current mode converter.

The converter has a filtered internal reference to achieve a low-noise output similar to low noise LDOs. The

converter achieves lower output voltage ripple by using a switching frequency of either 2.2 MHz or 1 MHz and a

larger inductance. The output voltage ripple can be further reduced by adding a small second stage L-C filter to

the output. This can be a ferrite bead or a small inductor, followed by an output capacitor. Internal compensation

maintains stability with an external filter inductor up to 50 nH. To avoid voltage drops across this second stage

filter, the device regulates the output voltage after the filter. The TPS6291x family supports an optional spread

spectrum modulation. When powering ADCs, for example, spread spectrum modulation reduces the mixing

spurs. Switching frequency, spread spectrum modulation, and output discharge are set using the S-CONF pin.

7.2 Functional Block Diagram

SW

MOSFET Driver

Anti Shoot Through

Converter Control Logic

High Side

Current Sense

Comparator

VIN

PGND

EN/SYNC

VO

FB

2nd stage filter

compensation

NR/SS

Output voltage

discharge

logic

PG

Undervoltage

lockout

Thermal shutdown

Slope

Compensation

0.8V

PSNS

1.0V

Low Side

Current Sense

S-CONF

G

+

t

+

t

ADC

Start-up readout

S-CONF

Register

Selection

MODE

MODE

1MHz/2.2MHz

MODE

MUX

Spread Spectrum

Modulation

MODE

Clock

Detector

Softstart

GM

GM Amplifier

+

t

EN/SYNC

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TPS62912, TPS62913

SLVSFP4 – AUGUST 2020

Copyright © 2020 Texas Instruments Incorporated

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Product Folder Links: TPS62912 TPS62913