TPS2111 output drop

takishin

Expert 2360 points

Other Parts Discussed in Thread: TPS2111, TPS2111A

Our customer has some questions about TPS2111.
I'm posting the questions for a customer:

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TPS2111 is AUTO-SWITCHING MODE (VSNS=Gnd) for testing.

D0=High,D1=Low (Output the higher voltage either of IN1 or IN2.)

IN1 =5.0V -> 0V(USB unpluged)
IN2 =3.3V

When IN1(5.0V) is unpluged(IN1=0V), the output changes to IN2(3.3V)
but the output voltage is droped before changing to IN2 voltage.
The drop period is so long(+3mS).
Output capacitor(22uF/47uF) can not fill the drop.

1)Why is the long drop generated ?

2)What should I do in order not to drop ?

Alternatively,
I have tested the circuit of datasheet:Figure 5.(D0=Low,D1=Low/High ).
It is no drop with 22uF-output capacitor.

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thanks in advance.

over 11 years ago

0 Eric Wright over 11 years ago

TI__Mastermind 42795 points

I do not notice a figure in TPS2111 datasheet for the auto switch over droop test with D1=0 and toggling of D0. I suspect that this is due to the performance that you have noticed.

I also looked in the TPS2111A datasheet and do find the auto-switch over droop test as shown below with a comment about TPS2111A vs. TPS2111 highlighted. My suggestion is to use the TPS2111A.

0 takishin over 11 years ago in reply to Eric Wright

Expert 2360 points

Hi Eric,

Thanks for your answer.

The TPS2111A data sheet says "*75% less* output voltage droop compared to TPS2111" in chart.
The drop period of TPS2111A is approximately 1 div(=250 us)in the chart,
but TPS2111 has about 3ms(too long?).

Has TPS2111A improved this point(long drop period)?

regards,
takishin

0 Eric Wright over 11 years ago in reply to takishin

TI__Mastermind 42795 points

Yes, the drop period is reduced with the "A" versions. Actual circuit performance will depend on your output capacitors.

0 MIKHAIL SALOV over 11 years ago in reply to Eric Wright

TI__Expert 6950 points

Good day Eric,

What is the duration of the voltage's droop without the capacitor on the output?

What is the value of the voltage's droop in mV?

Thank you, Mike

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TPS2111 output drop