Part Number: TMS570LC4357
Other Parts Discussed in Thread: ADC121C021
Hi.
Is there a data sheet for allowable signal source impedance of ADC?
In this circuit, the input to the microcomputer is about 4.05V, but the AD conversion result is about 2800 digits.(ADC:5V,12bit)
(2800digits x 0.00122mV = 3.416V)
Best regards.
t1.tif
Hi QJ,
Let me jump in as this question comes from my customer.
Customer wants to know “requirement for ADC source impedance” for correct ADC conversion results.
For example, our ADC121C021 datasheet says source impedance should be less than 100ohm.
https://www.ti.com/lit/ds/symlink/adc121c021.pdf
Please see page16.
Do we have similar guideline for Hercules ADC?
By the way, I found there is an application note discussed about it.
https://www.tij.co.jp/jp/lit/an/spna118b/spna118b.pdf?ts=1616567904874&ref_url=https%253A%252F%252Fwww.tij.co.jp%252Fsitesearch%252Fjp%252Fdocs%252Funiversalsearch.tsp%253FsearchTerm%253Dspna118
According to this document, the requirement depends on ADC parameters, Cext and sampling rate (Table 1 in the application note).
Is this what customer should refer to ?
Thanks and regards,
Koichiro Tashiro
