VIN = 8 - 17 V

VOUT = 3.3 V, 8 A

R7

10.0k

C7

47uF

C3

0.1uF

R6

0

R8

2.21k

R5

4.64k

C4

3900pF

C5

39pF

C1

10uF

R1

35.7k

R2

8.06k

R3

100k

1

RT/CLK

2

GND

3

GND

4

PVIN

5

PVIN

6

VIN

7

V_SNS

8

COMP

9

SS/TR

10

EN

11

PH

12

PH

13

BOOT

14

PWRGD

15

PWPD

U1

TPS54821RHL

C2

4.7uF

C6

0.022uf

C9

470pF

L1 3.3 uH

C8

47uF

R4

100k

EN

V_SNS

V_SNS

EN

PULL UP VOLTAGE

PWRGD

VIN

VOUT

21

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

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The TPS54821 is a highly-integrated, synchronous step-down dc-dc converter. The device is used to convert a

higher dc input voltage to a lower dc output voltage with a minimum output current of 8 A.

8.2 Typical Application

Figure 29. Typical Application Circuit

8.2.1 Design Parameters

This example details the design of a high frequency switching regulator design using ceramic output capacitors.

A few parameters must be known in order to start the design process. These parameters are typically determined

at the system level. For this example, use the parameters shown in Table 1.

Table 1. Design Parameters

PARAMETER

VALUE

Output Voltage

3.3 V

Output Current

8 A

Transient Response 4 A load step

ΔVout = 7 %

Input Voltage

12 V nominal, 8 V to 17 V

Output Voltage Ripple

33 mV p-p

Start Input Voltage (Rising Vin)

6.528 V

Stop Input Voltage (Falling Vin)

6.193 V

Switching Frequency

480 kHz