Datasheet
SLVS132F − NOVEMBER 1995 − REVISED OCTOBER 2004
24
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APPLICATION INFORMATION
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.
REG_IN
1 IN
GND
2 IN
REG_OUT
1 OUT
V
CC
2 OUT
U2
TPS2812D
1
2
3
4
8
7
6
5
Q1
IRF7406
13
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
V
I
V
I
GND
GND
3.3 V
3.3 V
GND
GND
U1
TL5001CD
OUT V
CC
COMP FB
GND RT 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%
8765
1234
+
+
++
+
Figure 48. 3.3-V 3-A Synchronous-Rectified Buck Regulator Circuit
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.