Datasheet


SLUS489 − OCTOBER 2001
18
www.ti.com
APPLICATION INFORMATION
where f
SW
is the switching frequency, L is the inductor value, and D is the duty cycle. The duty cycle for a buck
converter is defined as:
D +
V
OUT
V
IN
Note that in these equations the voltage drop across the rectifier has been neglected.
boost converter
The boost topology is simple and efficient, and should be used whenever the desired output voltage is greater
than the maximum input voltage. Figure 5 shows the TPS43000 in a typical (750 kHz) boost converter with an
input voltage range of 2.5 V to 4.5 V, an output voltage of 5.0 V, and a load current from 0 A to 1 A.
1
3
2
4
5
6
7
8
SYNC/SD
CCS
RT
CCM
BUCK
PFM
COMP
FB
TPS43000
9
10
11
12
13
14
15
16
VIN
VOUT
NDRV
GND
PDRV
VP
SWP
SWN
Q2
Si9803DY
D1
ZHCS1000
(OPTIONAL)
Q2
Si9804DY
UDG−01037
R3
24.9 kΩ
R5
1 kΩ
R4
49.9 kΩ
V
IN
V
OUT
C6
0.47 µF
C5
0.47 µF
C4
0.47 µF
C7
100 µF
L1
3.3 µH
R2
30.1 kΩ
R1
280 kΩ
C3
680 pF
C8
120 µF
V
IN
C2
330 pF
C1
3300 pF
R
BIAS
53.6 kΩ
Figure 5. 5-V Output Boost Topology
(18)