Datasheet


SLUS489 − OCTOBER 2001
21
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APPLICATION INFORMATION
flyback converter
A flyback converter (750 kHz) using the TPS43000 is shown in Figure 7. It uses a standard two-winding coupled
inductor with a 1:1 turns ratio. The advantage of this topology is that the output voltage can be greater or less
than the input voltage. For example, this is ideal for generating 3.3 V from a lithium-ion cell.
UDG−01039
C8
120 µF
C6
0.47 µF
V
OUT
V
IN
C4
0.47 µF
C5
0.47 µF
R3
6.81 kΩ
R5 1 kΩ
V
IN
R1
169 kΩ
R2
24.9 kΩ
R4
49.9 kΩ
R6 1 kΩ
L1A
3.3 µH
C7
100 µF
L1B
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
D1
ZHCS1000
(OPTIONAL)
Q1
Si9804DY
Q2
Si9803DY
PFM
R
BIAS
53.6 kΩ
C3
1200 pF
C1
3900 pF
C2
82 pF
Figure 7. 3.3-V Output Flyback Topology
NOTE: Resistor-capacitor snubbers can be placed across the primary and secondary windings to
reduce ringing due to leakage inductance. These are optional, and may not be required in the
application.
For a flyback converter, the average output current is related to the peak inductor current by: