ERROR

AMPLIFIER

Boot

Charge

UVLO

Current

Sense

Oscillator

with PLL

Slope

Compensation

Maximum

Clamp

Voltage

Reference

Overload

Recovery

VSENSE

SS/TR

COMP

RT/CLK

PH

BOOT

VIN

GND

Thermal

Hiccup

EN

Enable

Comparator

Shutdown

Logic

Shutdown

Enable

Threshold

Logic

Shutdown

PWRGD

EXPOSED THERMAL PAD

Power Stage

& Deadtime

Control

Logic

LS MOSFET

Current Limit

OV

Minimum Clamp

Pulse Skip

PVIN

UV

HS MOSFET

Current

Comparator

Current

Sense

Regulator

VIN

Boot

UVLO

PH

GND

PVIN

Hiccup

Shutdown

Hiccup

Shutdown

11

TPS54821

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SLVSB14B – OCTOBER 2011 – REVISED FEBRUARY 2016

Product Folder Links: TPS54821

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Copyright © 2011–2016, Texas Instruments Incorporated

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Fixed Frequency PWM Control

The device uses a adjustable fixed frequency, peak current mode control. The output voltage is compared

through external resistors on the VSENSE pin to an internal voltage reference by an error amplifier which drives

the COMP pin. An internal oscillator initiates the turn on of the high-side power switch. The error amplifier output

is converted into a current reference which compares to the high-side power switch current. When the power

switch current reaches current reference generated by the COMP voltage level the high-side power switch is

turned off and the low-side power switch is turned on.

7.3.2 Continuous Current Mode Operation (CCM)

As a synchronous buck converter, the device normally works in CCM (Continuous Conduction Mode) under all

load conditions.

7.3.3 VIN and Power VIN Pins (VIN and PVIN)

The device allows for a variety of applications by using the VIN and PVIN pins together or separately. The VIN

pin voltage supplies the internal control circuits of the device. The PVIN pin voltage provides the input voltage to

the power converter system.