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TPS54260: Hacking PMP5863 Reference Design for lower Vin

Part Number: TPS54260
Other Parts Discussed in Thread: TPS64200, TPS40000, TPS40040, TPS40021-EP, TPS40007, TPS65262-1, TPS53353, TPS53513, TPS53355, TPS53515, TPS53318, TPS53319, TPS53915

I am anxious to use the concepts presented in TI’s PMP5863 Reference Design demonstrating use of a buck converter to generate dual positive and negative rails to be cleaned up using TPS7A3001 and TPS7A4901 low noise linear regulators. The application is a power system providing low noise dual rails to an industrial analog data sensor ADC front end.

For my application the input voltage range would ideally be 1.6 to 6 VDC allowing use of a single 3.6 VDC Li cell, or a pair of alkaline cells in series discharged to ~0.8 VDC/cell. The issue I see is the TPS54260 used in PMP5863 is specified for a minimum of 3.5 VDC input. The circuit around TPS54260 as described in its datasheet 8.2.3 Split-Rail Power Supply section with more details of this dual positive+negative output technique in Application Report SLVA369A. Keying off SLVA369A I checked for buck controllers using TI’s web tools.

Starting with external switch types and the closest match to my specs found included TPS40021-EP, TPS40040/1, TPS40007/9, TPS40000/2 all with 2.25 Vin minimum or the TPS64200/1/2/3 series with 1.8 Vin minimum.

Moving to internal switch types (preferred for simplicity) the TPS65262-1/2 offers both 1.3 Vin minimum and multiple outputs. Adding single output types the TPS548D2x, TPS549D2x, TPS53915, TPS53515, TPS53513, TPS53318, TPS53319, TPS53353, and TPS53355 all bubble up with 1.5 Vin minimums.

Any suggestions on paring down this candidates list for a lower Vin minimum device to take the place of TPS54260? Are there other parts I should consider?