ADS7959: Reference input resistance at DC

Yuta Nishie

Genius 3615 points

Part Number: ADS7959

Hi,

The data sheet of ADS7959 states that the reference input resistance at 1MHz is 100kΩ (Typ).

Please tell me the reference input resistance value (min, Typ and Max) when DC (0Hz) is input.

Best Regards,

Nishie

over 3 years ago

+1 Tom Hendrick over 3 years ago

TI__Guru**** 173996 points

Hi Nishie,

The 1k reference impedance spec of the ADS7959 is specified at 1M sampling rate - the actual signal applied to the reference input is DC. We have a great series of videos on driving the reference input to SAR converters. I suggest you look over section 9 which deals with the reference input . We do not have min and max values to share as this is not a production tested feature.

0 Yuta Nishie over 3 years ago in reply to Tom Hendrick

Genius 3615 points

Hi Tom Hendrick-San,

Thank you for your reply.

I found that there was no min value and max value.

Please tell me how much it actually fluctuates from Typ 100kΩ.

Also, when Vref = 2.5V + -0.1V, Typ = 100kΩ is fine, isn't it?

Best Regards,

Nishie

+1 Tom Hendrick over 3 years ago in reply to Yuta Nishie

TI__Guru**** 173996 points

The impedance could vary +/-10%. The ADS7959 is an 8-bit converter, so a variation of +/-0.1V on the reference is about 10 codes. If that meets your end equipment performance needs, than yes, it is fine.

0 Yuta Nishie over 3 years ago in reply to Tom Hendrick

Genius 3615 points

Thank you for your support.

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ADS7959: Reference input resistance at DC