TPS61022: Output maximal capacitive load

Matteo Bolognesi

Part Number: TPS61022

Tool/software:

The datasheet gives 1000uF as "Effective output capacitance range".
We will use the TPS61022 to raise a voltage to 3.6V with 2.5A, this circuit need to power our electronics board that has on the power input 4 capacitors in parallel of 6800uF. Is this a problem that may cause a problem on the feedback or instability of the converter?
If is the case adding a diode in series between the output of the TPS61022 and the capacitors can solve the problem?

Thanks

2 months ago

0 Lei Zhong 2 months ago

TI__Mastermind 18700 points

Hi Matteo,

6800μF output capacitance is really large, and there are indeed instability concerns. But I think you may still have a try and test on the actual board. The most effective way to improve the stability is to add a feedforward cap. The initial feedforward zero can be put at 2kHz. If the instability is still there, then use feedforward cap with bigger capacitance to make the feedforward zero smaller.

Regards

Lei

0 Matteo Bolognesi 2 months ago in reply to Lei Zhong

Prodigy 35 points

Actually we have 4x6800uF, even much higher. Adding a rectifier diode will change something? Should we remove those capacitors instead? Thanks

0 Lei Zhong 2 months ago in reply to Matteo Bolognesi

TI__Mastermind 18700 points

Hi Matteo,

To avoid the confusion, could you provide a simple drawing to show where the diode is inserted?

Regards

Lei

0 Matteo Bolognesi 2 months ago in reply to Lei Zhong

Prodigy 35 points

Hello Lei, I've attached the picture showing in blue the diode and the capacitor.

+1 Lei Zhong 2 months ago in reply to Matteo Bolognesi

TI__Mastermind 18700 points

Hi Matteo,

As my understanding, inserting a diode between the output and the big Cout may not be helpful in the stability improvement.

One more suggested trying is adding a resistor in series with the 6800μF output cap. The purpose is to make the ESR zero much smaller to cancel the small output pole(because of large Cout). In the initial trying the resistance can be around 1Ω.

Regards

Lei

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TPS61022: Output maximal capacitive load