BUF16821-Q1: application concern about the isolation resistor values for a range of capacitance

user4782171

Intellectual 1560 points

Part Number: BUF16821-Q1

Hi all,

There has a RISO vs CLOAD application that need your help for it. There has a table about RISO vs CLOAD in SBOA134.

But my customer would like to use 10ohm vs 10uF for VCOM output due to can let VCOM ripple&noise from 800mV to 150mV.

Need your help to have the suggestion with Gain and Phase margin analysis for it.

Best regards,

Albert Lee.

over 5 years ago

0 Aaron Goodson over 5 years ago

TI__Expert 6330 points

Hi Albert,

I have notified our expert regarding this topic. Please expect a response by 1/14/19.

Thanks,

Aaron

0 Costin Cazana over 5 years ago

TI__Expert 4940 points

Hi Albert,

The phase margin can not be measure, I'll check next week transient response with RISO=10ohm and CLOAD=10uF

Regards,
Costin

0 Costin Cazana over 5 years ago in reply to Costin Cazana

TI__Expert 4940 points

Hi Albert,

RISO=10ohm will slow down the ramp up. The output buffer is stable and it will settle in ~500uS

I did a comparison Cload=10uF with/out RISO=10ohm, capacitor without RISO has marginal stability-ringing due to fast transient

Fast ramp-up trace : Cload=10uF

Slow ramp up trace ; Cload=10uF RISO=10ohm

Vin=8V

DAC=1F0 to DAC=1FF

Regards,

Costin

0 Costin Cazana over 5 years ago in reply to Costin Cazana

TI__Expert 4940 points

Hi Albert,

I haven’t heard back from you, I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has locked due to time-out)

Regards,
Costin

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BUF16821-Q1: application concern about the isolation resistor values for a range of capacitance