REG_IN

1 IN

GND

2 IN

REG_OUT

1 OUT

VCC

2 OUT

U2

TPS2812D

1

2

3

4

8

7

6

5

Q1

IRF7406

1

3

2

R5

10 kΩ

C11

0.47 µF

C100

100 µF

16 V

C5

100 µF

16 V

1

2

3

4

J1

2

1

Q2

IRF7201

3

CR1

30BQ015

C6

1000 pF

R7

3.3 Ω

L1

27 µF

C12

100 µF

16 V

C7

100 µF

16 V

C13

10 µF

10 V

1

2

3

4

J2

VI

I

V

GND

GND

3.3 V

3.3 V

GND

GND

U1

TL5001CD

OUT

VCC

COMP

FB

GND

R

T

DTC

SCP

R2

1.6 kΩ

C3

0.0022

µF

C2

0.033 µF

R13

10 kΩ

C14

0.1 µF

R6

15 Ω

R10

1 kΩ

R11

30 kΩ

CR2

BAS16ZX

R12

10 kΩ

CR3

BAS16ZX

C15

1 µF

R8

121 kΩ

1%

C9

0.22 µF

C1

1 µF

R4

2.32 kΩ

1%

R3

180 Ω

C4

0.022 µF

R1

1.00 kΩ

1%

R9

90.9 kΩ

1%

8

7

6

5

1

2

3

4

+

+

+

+

+

TPS2811-Q1

www.ti.com

SLVSAE0 – JUNE 2010

Synchronous Buck Regulator

Figure 48 is the schematic for a 100-kHz synchronous-rectified buck converter implemented with a TL5001

pulse-width-modulation (PWM) controller and a TPS2812 driver. The bill of materials is provided in Table 1. The

converter operates over an input range from 5.5 V to 12 V and has a 3.3-V output capable of supplying 3 A

continuously and 5 A during load surges. The converter achieves an efficiency of 90.6% at 3 A and 87.6% at 5 A.

Figures 49 and 50 show the power switch switching performance. The output ripple voltage waveforms are

documented in Figures 54 and 55.

The TPS2812 drives both the power switch, Q2, and the synchronous rectifier, Q1. Large shoot-through currents,

caused by power switch and synchronous rectifier remaining on simultaneously during the transitions, are

prevented by small delays built into the drive signals, using CR2, CR3, R11, R12, and the input capacitance of

the TPS2812. These delays allow the power switch to turn off before the synchronous rectifier turns on and vice

versa. Figure 51 shows the delay between the drain of Q2 and the gate of Q1; expanded views are provided in

Figures 52 and 53.

NOTE: If the parasitics of the external circuit cause the voltage to violate the Absolute Maximum Rating for the Output pins,

Schottky diodes should be added from ground to output and from output to VCC.

Figure 48. 3.3-V 3-A Synchronous-Rectified Buck Regulator Circuit

Copyright © 2010, Texas Instruments Incorporated

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