8 Detailed Description

8.1 Overview

The TPSM8281x synchronous switch mode DC/DC converter power modules are based on a fixed-frequency

peak current-mode control topology. The control loop is internally compensated. To optimize the bandwidth of

the control loop to the wide range of output capacitance that can be used with the TPSM8281x, one of three

internal compensation settings can be selected. See Section 8.3.3. The compensation setting is selected either

by a resistor from COMP/FSET to GND, or by the logic state of this pin. The regulation network achieves fast

and stable operation with small external components and low-ESR ceramic output capacitors.

The devices support fixed-frequency forced PWM operation with the MODE/SYNC pin tied to a logic high level.

When the MODE/SYNC pin is set to a logic low level, the device operates in power save mode (PFM) at

low-output currents and automatically transitions to fixed-frequency PWM mode at higher output currents. In

PFM mode, the switching frequency decreases linearly based on the load to sustain high efficiency down to very

low output currents. The device can be synchronized to an external clock signal in a range from 1.8MHz to 4MHz

applied to the MODE/SYNC pin.

8.2 Functional Block Diagram

+

-

GND

FB

VOUT

VIN

EN

Oscillator

Gate Drive and Control

Device

Control

PG

Thermal

Shutdown

Bias

Regulator

gm

Ipeak

VFB

SS/TR

COMP/FSET

MODE

Izero

470nH

SW

Output

Discharge

Rdis

8.3 Feature Description

8.3.1 Precise Enable (EN)

The TPSM8281x starts operation when the rising EN threshold is exceeded. For proper operation, the EN pin

must be terminated and must not be left floating. Pulling the EN pin low forces the device into shutdown. In

this mode, the internal high-side and low-side MOSFETs are turned off and the entire internal control circuitry is

switched off. The voltage applied at the EN pin of the TPSM8281x is compared to a fixed threshold of 1.1V for a

rising voltage.

The enable input threshold for a falling edge is typically 100mV lower than the rising edge threshold. The Precise

Enable input provides a user-programmable undervoltage lockout by adding a resistor divider to the input of the

EN pin. The Precise Enable input also allows you to drive the pin by a slowly changing voltage and enables

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TPSM82810, TPSM82813

SLUSDN6B – SEPTEMBER 2019 – REVISED JULY 2024

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Product Folder Links: TPSM82810 TPSM82813