7 Detailed Description

7.1 Overview

The TPS61322xx is a low quiescent current, high efficiency synchronous boost converter. The TPS61322xx

uses hysteretic current control scheme. The TPS61322xx is designed for systems powered by alkaline battery,

NiMH rechargeable battery, Li-ion battery or Li-polymer battery. The input voltage range is from 0.9 V to

5.5 V. After start-up is completed, the TPS61322xx can work with the input voltage down to 0.4 V. The

TPS61322xx consumes only 6.5-µA quiescent current and achieves high efficiency under light load conditions.

The TPS61322xx is designed as an always-on power. Higher than 90% efficiency is achieved under 10-mA

load from 1.5-V input voltage to 2.2-V output voltage conversion to extend battery lifetime. The TPS613222A

can support as high as 500-mA output current from 3-V input voltage to 5-V output voltage conversion with an

external schottky diode in parallel with internal high-side MOSFET.

7.2 Functional Block Diagram

Thermal

Shutdown

UVLO

Gate Driver

PWM Control

1

3

2

Logic

EA

VOUT

GND

Gate Driver

Current

Sense

VOUT

VREF

Soft Start &

Current Limit

Control

SW

VOUT

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7.3 Feature Description

7.3.1 Soft Start

When the input voltage is applied, the high side MOSFET is turned on. The input voltage charges the output

capacitors through the inductor and the high side MOSFET. When the output capacitors are charged to 0.83-V

typical value, the TPS61322xx starts switching at 1.6-MHz fixed frequency and the high-side MOSFET is turned

off. When the output voltage goes up to typical 1.6 V, an internal soft-start control circuit ramps the reference

voltage to 0.8 V within 2 ms. In this way, the soft-start function reduces the input inrush current. After the output

voltage reaches the target value, soft start ends, and the inductor peak current is determined by the output of an

internal error amplifier. After start-up, the TPS61322xx can work with the input voltage down to 0.4 V.

7.3.2 Boost Controller Circuit

The TPS61322xx boost converter is controlled by a hysteretic current mode scheme. The TPS61322xx regulates

the output voltage by keeping the inductor ripple constant of 200-mA typical value and adjusting the offset of

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TPS61322

SLVSDY5E – JANUARY 2018 – REVISED FEBRUARY 2024

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Product Folder Links: TPS61322