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Hi team,
I have checked below the process when the LDO output is not used, what capacitance does the small ceramic capacitor refer to?
What is the recommended capacitor size?
Sincerely.
Ryu
Hello Ruy,
I have assigned this to product expert. Please expect answer by tomorrow.
Datasheet specification seems to indicate minimum capacitance of 2.2uF, so at least with that value the LDO is proven and tested to be stable and not trigger false faults etc. I'll let Brenda to elaborate if she knows the minimum value in no load condition.
Thanks.
Regards,
Tomi Koskela
Hi Ryu,
You can use the minimum output capacitance in the spec for the unused LDO. I recommend using 2.2uF as Tomi recommended to make the rail is stable and doesn't trigger any false faults.
Thanks,
Brenda
Hi Brenda and tomi,
Thanks for the reply.
I understand that 2.2μF is recommended.
I think it should be as small as possible, but up to how much is acceptable to connect?
Sincerely.
Ryu
Hi Ryu,
2.2uF would be our recommendation as it is the capacitance value we have validated across temperature for the stability of the LDO.
Thanks,
Brenda
Hi Brenda,
Thanks for the reply.
I understood it well.
Sorry for asking so many questions.
I would like to know the maximum possible connection.
Sincerely.
Ryu
Hi Ryu,
What do you mean by "maximum possible connection"? What are you referring to?
Thanks,
Brenda
Hi Brenda,
The maximum capacitance of the capacitor to be connected.
I would like to check how much larger capacitor than 2.2μF can be connected.
Sincerely.
Ryu
Hi Ryu,
In the TPS650250 spec we only specify the minimum capacitance required for the stability of the LDO. This device has an evaluation module (TPS650250EVM-447) that can be used to evaluate the PMIC performance under different conditions. Output voltages as well as external passive components like output caps can be changed as needed to match specific application use cases.
Thanks,
Brenda
Hi Brenda,
What I am asking is the capacitance of the capacitor when the LDO is not used.
I would like to know the maximum value that can be connected in this case.
Because the answers in other threads stated that it should be as small as possible.
Sincerely.
Ryu
Hi Ryu,
Even though your application will not be using one of the LDOs, the minimum output capacitance (2.2uF) is still required for the unused LDO because both regulators share the same enable signal. For the unused LDO, the critical parameter would be the minimum capacitance for stability which is the 2.2uF we specify in our datasheet. The maximum capacitance for an unused rail should not be a concern because there wont be any load connected to the output so you just need the minimum capacitance to keep the overall power area small. Could you please share more information on your concern related to the maximum capacitance for the unused LDO?
Thanks,
Brenda
Hi Brenda,
Thanks for the reply.
I understand now.
I asked because it said that I need to connect as small a capacitance as possible.
For example, if I don't have a 2.2μF capacitor, can I connect a 10μF capacitor?
Sincerely.
Ryu
Hi Ruy,
In the other thread it was mentioned to use a small ceramic capacitor for the unused output. Small was just indication of low cost/small board area etc. because it is not critical for performance. It did not say as small as possible. As long as the value is 2.2uF or higher you are fine.
Thanks.
Regards,
Tomi Koskela