TPS62088: output capacitance

Isee

Part Number: TPS62088
Other Parts Discussed in Thread: TPS628513

As per datasheet, recommended is 2x10uF or one 22uF

let's assume for 3.3V output voltage.
Customer is currently using 2x10uF .

What if 5cm away there is an IC, that "requires" 100uf of decoupling capacitance on this 3.3V line?
Is this still in spec or out of it?

Regards

Andreas

7 months ago

0 Varun John 7 months ago

TI__Genius 15390 points

Hi Andreas,

From testing on this device family, the extra inductance between the bulk and local caps close to DC-DC output doesn't really help reduce the influence of the bulk caps on phase margin.

You could consider using TPS628513 to support higher output caps.

Best regards,

Varun

0 Isee 7 months ago in reply to Varun John

TI__Expert 5370 points

hi Varun,

is there any way to check for the phase margin?
I've checked the webench tool, but it can only simulate start-up, transients, and steady state.

Typically we use the IC for 1.8V supply instead of an ldo, because of low quiescent current and efficiency.
Power requirements are low, below 0.5A in worst case.

Regards

Andreas

0 Varun John 7 months ago in reply to Isee

TI__Genius 15390 points

Hi Andreas,

If the board is already manufactured, it would be best to run a Bode plot measurement on the board.

We don't have a SPICE average model for this device, so it won't be possible to run an AC sim using Webench to get phase margin.

Phase margin can be indirectly estimated by running a fast load transient sim on the PSPICE transient model. This app note shows how to correlate the number of output ringing cycles to the phase margin https://www.ti.com/lit/an/slva381b/slva381b.pdf

Best regards,

Varun

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TPS62088: output capacitance