Datasheet


SLUS489 − OCTOBER 2001
17
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APPLICATION INFORMATION
design examples: buck, boost, non-synchronous boost, flyback, and SEPIC
buck converter
The buck topology is simple and efficient, and should be used whenever the desired output voltage is less than
the minimum input voltage. Figure 4 shows the TPS43000 in a typical (750 kHz) buck converter with an input
voltage range of 3.0 V to 9.0 V, an output voltage of 2.7 V, and a load current from 0 A to 2 A.
UDG−01035
R4
49.9 kΩ
R3
49.9 kΩ
R2
75 kΩ
53.6 kΩ
1
3
2
4
5
6
7
8
SYNC/SD
CCS
RT
CCM
BUCK
COMP
FB
TPS43000
9
10
11
12
13
14
15
16
VIN
VOUT
NDRV
GND
PDRV
VP
SWP
SWN
C7
100
µ
F
C1
560 pF
C3
100 pF
L1
3.3
µ
H
C6
0.47
µ
F
C2
10 pF
R
BIAS
C4
0.47
µ
F
Q2
Si9803DY
Q1
Si9804DY
D1
ZHCS1000
(OPTIONAL)
C5
0.47
µ
F
PFM
C8
120 µF
V
IN
V
OUT
V
IN
V
IN
R5
1 kΩ
R1
127 kΩ
Figure 4. 2.7-V Output Buck Topology
For a buck converter, the average output current is related to the peak inductor current by:
I
pk
+ I
OUT
)
ǒ
V
IN
* V
OUT
Ǔ
D
ǒ
2 f
SW
L
Ǔ
(17)