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TPS784-Q1: Output Accuracy Comparison between LDO and Buck (TPS784-Q1, TPS629203)

Jade Han
Prodigy 690 points
Part Number: TPS784-Q1
Other Parts Discussed in Thread: TPS629203

Hello,

I had some questions on specifics of LDO and Buck's accuracy.

I am trying to compare the accuracy of LDO and buck through lab test.

For LDO, I am using TPS784-Q1 and for Buck, I am using TPS629203.

To be more specific, I am using TPS629203-Q1EVM for buck EVM.

I was looking at the datasheet, but I am confused on which values I should be comparing in order to correctly compare the accuracy.

Resistor tolerance is not included in the LDO's overall accuracy, so I was wondering which values from the datasheets can pair up or match, for the comparison.

TPS784-Q1 (LDO)

TPS629203 (Buck)

I also had several questions on this matter.

1) In the buck image above, what is the difference between output voltage regulation and feedback voltage regulation?

2) For LDO and buck each, which values should I refer to for the finalized accuracy, with all of the resistor tolerance considered? If it is not shown in the chart above, how can I calculate it with the values above?

3) For this LDO, when the resistor error should be under 1%, what is the output accuracy or regulation for the VSET option and FB option, respectively?

Thank you.

  • 0
    TI__Genius 12345 points

    Hi Jade

    For the TPS784-Q1, I assume you are using the adjustable version.

    You could refer to the Output Accuracy Plots under section 6.6 of the DS and then include the tolerance % of your expected resistor.

    You can also follow the following App note to understand how to include the Resistor tolerance into your calculations.  

    Effect of Resistor Tolerances on Power Supply Accuracy

    This can also be applied to the Buck converter. 

    I'm afraid TPS784-Q1 does not have a VSET pin, this is included on the Buck not the LDO. 

    I will be redirecting you to the corresponding group for the TPS629203. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    TI__Mastermind 45820 points

    Hi Jade,

    For TPS629203, feedback voltage regulation is only accuracy of feedback 0.6V itself and does not include external feedback resistor tolerance. The application note which Edgar referred can be  applied to Buck converter. VSET means internal feedback without external feedback resistors needed. It is very good feature to save BOM cost. So output voltage regulation is overall accuracy which including internal resistors. Please refer to datasheet Table 8-1 for configuration.

    Hope this helps,

    Thanks,

    Nancy