TLV758P: About the startup waveform

Andy Liu3

Part Number: TLV758P
Other Parts Discussed in Thread: MULTIPKGLDOEVM-823,

Hello,

I test the TLV75801PDBVR on MULTIPKGLDOEVM-823 board. And I use the typical application, set input and output capacitor 0.1uF+1uF+10uF ceramic capacitors, and use R1=11K, R2=25K to set output voltage 1.8V.

I use input 2V, 3.3V, 5.4V test load 0A, 0,25A and 0.5A, find that the output waveform of LDO have a back groove, at the same time the input voltage has reached the turn-on voltage.

I have change the input and output capacitors but the groove always exist.

Please see the attachment for waveform.tlv758P.xlsx

over 3 years ago

0 JCHK over 3 years ago

TI__Mastermind 43580 points

Hi Andy,

Are you testing with an electronic load? Do you see the same behavior with a purely resistive load?

An electronic load can cause interesting behaviors.

I hope this gives some insight.

0 Andy Liu3 over 3 years ago in reply to JCHK

TI__Intellectual 2500 points

Hi John,

Thank you very much,

I tested with an electronic load before. And I test with a purely resistive load with the same test environment, and the groove is disappear

Please see the attachment for waveform. TLV758P_resistive load.xlsx

Could you please help me answer the question the difference between electronic loads and resistive loads or recommended some information?

Thanks

0 JCHK over 3 years ago in reply to Andy Liu3

TI__Mastermind 43580 points

Hi Andy,

Electronic loads have a complex impedance that attempts to sink the same current regardless of the voltage. This can lead to some odd behavior when ramping a voltage into an electronic load.

As resistive load is simply resistive. It can only sink current as I=V/R.

I hope this helps to answer your question.

0 Andy Liu3 over 3 years ago in reply to JCHK

TI__Intellectual 2500 points

Hi, JCHK,

thanks your help.

Thanks.

Best Regards.

Andy Liu

Power management

Power management forum

TLV758P: About the startup waveform