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Inverting Buck Boost using a TI Synchronous step down regulator

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: LM5160

Hello,

There is the application of "Creating an Inverting Power Supply Using a Synchronous Step-Down Regulator"

http://www.ti.com/lit/an/slva524/slva524.pdf

Can this application note be used for all TI's synchronous step-down DCDC?
For example, there are DCS, DCAP, CoT, current mode, voltage mode topology, but can we use this application note for these typologies?
Please let me know if you have any concern.

Also, can I LM5160 as inverting power supply? LM5160 is constant ontime. And Ron is connected to Vin.
Thus, the switching frequency at start up is gradually change.


Best Regards,
Ryuji Asaka

  • 0
    Prodigy 5 points
    Hello Ryuji, I apologize for the late reply.
    In general, YES, tying the buck inductor to ground can be used to create an inverting topology with most all buck controllers and converters.
    The IC does not know the difference.

    What is important to remember are 2 things.
    1. the IC ground is at the negative rail output. This means any control signals above ground must be level shifted to the IC.
    Enable, Power good, things like that.
    2. Voltage across the power stage is VIN summed with [Vout-] (magnitude)
    example; 5Vin to -10Vout, total voltage is 15V across the power stage
    Similar to boost equations, you would be boosting from 5Vin to 15Vout.

    This document shows the governing equations;
    Power Topologies Poster (Rev. F) www.ti.com/.../sluw001f