7 Detailed Description

7.1 Overview

The TPSM8291x low-noise, low-ripple synchronous buck converter module is a fixed frequency current mode

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

to low-noise LDOs. The converter module achieves lower output voltage ripple by using a switching frequency

of either 2.2 MHz or 1 MHz and an integrated 2.2-μH inductor. 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 TPSM8291x family supports an optional spread spectrum modulation. For example, when powering ADCs,

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

VOUT

MOSFET Driver

Anti Shoot Through

Converter Control Logic

High Side

Current Sense

Comparator

VIN

PGND

EN/SYNC

FB

2nd stage filter

compensation

NR/SS

Iss

Output voltage

discharge

logic

VPG

PG

VFB

Undervoltage

lockout

Thermal shutdown

Slope

Compensation

VREF

0.8V

Rf

PSNS

1.0V

Low Side

Current Sense

S-CONF

GGG

+

t

+

t

+

t

+

t

+

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

VIN

VIN

RDIS

2.2 µH

220 nF

www.ti.com

TPSM82913

SLVSGJ4A – OCTOBER 2022 – REVISED DECEMBER 2022

Copyright © 2022 Texas Instruments Incorporated

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Product Folder Links: TPSM82913