ADS4225: ADS4225

Michael Steffes

Part Number: ADS4225

Hey guys, starting to do a filter design in front of this device.

My experience with unbuffered pipeline inputs is that they will have a clock rate dependent common mode current - sometimes shown as a uA/MHz spec. This is important for Vcm level shift in DC coupled inputs via the filter impedances. I do not see that spec in the PDS.

I am almost 100% sure it is physically there, can I get a spec?

over 5 years ago

0 Jim Brinkhurst1 over 5 years ago

TI__Mastermind 44560 points

Hi Michael
I'm looking into this and will add another post once I have more information to share.
Best regards,
Jim B

0 Jim Brinkhurst1 over 5 years ago in reply to Jim Brinkhurst1

TI__Mastermind 44560 points

Hi Michael
There is a spec for this in Table 8.7 on page 18 of the datasheet.
"Analog input common-mode current"
Best regards,
Jim B

0 Michael Steffes over 5 years ago in reply to Jim Brinkhurst1

Guru 48395 points

Thanks, should have looked closer

1.5uA/MSPS

so at 125MSPS that is .197mA common mode - yes if my series filter element is say 40ohms, that is a 7.5mV IR drop - can adjust the FDA Vcm up to account for that.

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ADS4225: ADS4225