TLC1543: TLC1543 A0~A10 noise issue

Kevin Huang8

Part Number: TLC1543
Other Parts Discussed in Thread: TLV1543

Hi Sir,

When TLC1543 Sample status,will measure A0~A10 pin will have noise issue, Is there a root cause for this noise? please check below waveform. measured

1 month ago

0 Tom Hendrick 1 month ago

TI__Guru*** 137265 points

Hi Kevin,

Thank you for the great TLV1543 question! The first post you made you mentioned only CH9 and in this post you imply that all channels are impacted by this noise. Can you please tell at which point in the schematic was the scope shot you provided captured? Can you describe what (schematically) is to the left of A0..A5 and A9? Can you also provide details on the AD_CK and AD_CS? Finally, please tell us about the conversion results - are they correct, do you see offset in the conversion result, etc.

0 Kevin Huang8 1 month ago in reply to Tom Hendrick

Intellectual 865 points

Hi Tom,

As below is test waveform.

Waveform.doc

0 Kevin Huang8 1 month ago in reply to Tom Hendrick

Intellectual 865 points

Hi Tom,

As below is test waveform.

2134.Waveform.doc

0 Tom Hendrick 1 month ago in reply to Kevin Huang8

TI__Guru*** 137265 points

Hi Kevin,

Thanks for the added detail! The TLV1543 is a succesive approximation register (SAR) type ADC. The ability of the internal sample and hold cap to charge to within 1/2 LSB (ideally) of the new sample depends on the input impedance and the drive capability of whatever amplifier might be attached to the input. Here is a series of informative videos to help explain a little about the nuiances of driving a SAR converter.

Data converters

Data converters forum

TLC1543: TLC1543 A0~A10 noise issue