TPS563208: Calculating maximum output voltage ripple

Lukasz Przenioslo

Part Number: TPS563208

Hello there,

I am trying to calculate the maximum output voltage ripple for a device using the TPS563208. I need to know, how to optimize the output capacitors value for the given (known) maximum load, inductor value, and input/ output voltage.

I am referring the SLVSD90 and the SLVA630A, but cannot find a generic equation to do that. I would appreciate all help.

over 4 years ago

0 Gerold Dhanabalan - Online Design Tools over 4 years ago

TI__Genius 14455 points

If you look at equation 26 (section 8) of the document, it has a generic equation at the same time very accurate to calculate the output ripple.

https://www.ti.com/lit/an/slva630a/slva630a.pdf

If you need an approximate ripple, you can go with equation 24 ( it is simple but not accurate).

If you look at equation 26, it does not directly list L or Fsw. But the Ip2p is dependent on L and Fsw which brings the dependency here - if thats what you are looking for.

Regards,

Gerold

0 Lukasz Przenioslo over 4 years ago in reply to Gerold Dhanabalan - Online Design Tools

Expert 2630 points

Thank you for the answer,

Is it correct that the input voltage value does not play any role in the output voltage ripple calculation? Its not present in any given equations:

0 Lukasz Przenioslo over 4 years ago in reply to Lukasz Przenioslo

Expert 2630 points

Hi,

Here is what I am stuck with when trying to calculate the output voltage ripples. The slva630a gives the following, simplified equation:

where:

C- output capacitance,
R - ESR value of the output capacitance
F_SW- Switching frequency- can I assume max frequency here, i.e. 580-kHz for the TPS563208?
I_p2p: this has to be calculated.

Reading from the TPS563208 datasheet:

where:

V_out- set output voltage,
V_IN(MAX): maximum input voltage,
f_sw: same switching frequency as above?
L_O: Is this the inductor value?

Here I am not sure why aren't these equations dependent on the maximum load current?

I would appreciate further help.

0 Vincent Zhang(BSR) over 4 years ago in reply to Lukasz Przenioslo

TI__Expert 4795 points

Yes the output ripple depends on current ripple, not relative to DC value.

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TPS563208: Calculating maximum output voltage ripple