Datasheet
+
9-21V
VIN
C1
ENA
VIN
ENA
NC
NC
GND
PwPd
BOOT
PH
VSNS
U1
TPS5431DDA
C2
0.01 Fm
L1
18 Hm
D1
B340A
C3
220 Fm
R2
3.24kW
5V
VOUT
R1
10kW
C3=SanyoPOSCAP 10TP220M
+
10-35V
VIN
C1
4.7 Fm
C4
4.7 Fm
ENA
VIN
ENA
NC
NC
GND
PwPd
BOOT
PH
VSNS
U1
TPS5430DDA
C2
0.01 Fm
L1
22 Hm
D1
B340A
C3
220 Fm
R2
3.24kW
5V
VOUT
R1
10kW
C3=SanyoPOSCAP 10TP220M
TPS5430
TPS5431
SLVS632E –JANUARY 2006–REVISED SEPTEMBER 2013
www.ti.com
Catch Diode
The TPS5430 is designed to operate using an external catch diode between PH and GND. The selected diode
must meet the absolute maximum ratings for the application: Reverse voltage must be higher than the maximum
voltage at the PH pin, which is VINMAX + 0.5 V. Peak current must be greater than IOUTMAX plus on half the
peak to peak inductor current. Forward voltage drop should be small for higher efficiencies. It is important to note
that the catch diode conduction time is typically longer than the high-side FET on time, so attention paid to diode
parameters can make a marked improvement in overall efficiency. Additionally, check that the device chosen is
capable of dissipating the power losses. For this design, a Diodes, Inc. B340A is chosen, with a reverse voltage
of 40 V, forward current of 3 A, and a forward voltage drop of 0.5 V.
Additional Circuits
Figure 12 and Figure 13 show application circuits using wide input voltage ranges. The design parameters are
similar to those given for the design example, with a larger value output inductor and a lower closed loop
crossover frequency.
Figure 12. 10–35 V Input to 5 V Output Application Circuit
Figure 13. 9–21 V Input to 5 V Output Application Circuit
Circuit Using Ceramic Output Filter Capacitors
Figure 14 shows an application circuit using all ceramic capacitors for the input and output filters which generates
a 3.3-V output from a 10-V to 24-V input. The design procedure is similar to those given for the design example,
except for the selection of the output filter capacitor values and the design of the additional compensation
components required to stabilize the circuit.
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