1 Basic Buck Topology
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Vin
Vout
Feedback
Network
Lout
Cout
Catch
Diode
BootCapacitor
Cin
FET
Switch
REF
Error Amp
PWMControl
&GateDrive
IntegratedFunctions
Application Report
SLVA257A – January 2007 – Revised August 2007
Using the TPS5430 as an Inverting Buck-Boost Converter
John Tucker ........................................................................................................ PMP Systems Power
ABSTRACT
The wide input voltage range SWIFT™ (Switcher With Integrated FET) dc/dc
converters are typically used as step-down converters where the derived output is a
positive voltage less than the input voltage source. In some cases, it may be required
to generate a negative voltage from the input voltage source. In such instances, it is
possible to configure the TPS5430/20/10 devices in an inverting buck–boost topology,
where the output voltage is negative with respect to ground.
Contents
1 Basic Buck Topology ............................................................................... 1
2 Inverting Buck-Boost Topology ................................................................... 2
3 Design Considerations ............................................................................. 2
4 Circuit Performance ................................................................................ 4
5 Conclusion ........................................................................................... 7
List of Figures
1 Buck Topology ...................................................................................... 1
2 Inverting Buck-Boost Topology ................................................................... 2
3 TPS5430 Buck–Boost Application ................................................................ 3
4 Closed Loop Response ............................................................................ 4
5 Transient Response ................................................................................ 5
6 Output Voltage Ripple and PH Node Voltage .................................................. 5
7 Efficiency ............................................................................................. 6
8 Load Regulation .................................................................................... 6
To understand the circuit operation, consider the basic topology of the buck converter as shown in
Figure 1 .
Figure 1. Buck Topology
SWIFT, PowerPAD are trademarks of Texas Instruments.
SLVA257A – January 2007 – Revised August 2007 Using the TPS5430 as an Inverting Buck-Boost Converter 1
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