0
\$\begingroup\$

From the datasheet for the TS971... The absolute maximum differential input voltage is ±1V.

How concerned must I be with that if I am buffering a square wave whose amplitude exceeds 1V? In the buffer configuration, of course, the output is connected to the inverting input, so any change in the non-inverting input will be followed by the exact same change in the inverting input. Does this absolute maximum specification care about short term transients like that or is it just worrying about the case where someone might (for example) try to use the amp as a comparator with a very wide delta?

\$\endgroup\$
5
  • \$\begingroup\$ Insufficient design details on reactive loads and input R's \$\endgroup\$
    – D.A.S.
    Commented Aug 31, 2021 at 1:43
  • \$\begingroup\$ Did you work on AMR? I did once, but when our company went under, all the patents and specs for our 2 way wireless meter reading network and database interface patents were sold to Itron. (Iris Sys) \$\endgroup\$
    – D.A.S.
    Commented Aug 31, 2021 at 2:57
  • \$\begingroup\$ I kinda do, but my day job is software. My posts here are all related to my various hobbies. \$\endgroup\$
    – nsayer
    Commented Aug 31, 2021 at 4:14
  • \$\begingroup\$ We had a couple dozen H/W and 2 dozen S/W experts put out network together into any client head-end database for real-time or polled ISM band network at 928MHz with 8kHz BW multiplexed in time, space (colours) These were designed 25 yrs ago to retrotfit any existing mechanical meter for power sensing \$\endgroup\$
    – D.A.S.
    Commented Aug 31, 2021 at 4:20
  • 1
    \$\begingroup\$ I like your hobbies \$\endgroup\$
    – D.A.S.
    Commented Aug 31, 2021 at 4:26

1 Answer 1

Reset to default
1
\$\begingroup\$

The inputs have dual diodes for ESD protection, so current limiting the inputs is a MUST.

My guess (based on most designs) <5 mA to prevent Vdiff >1V. They have to use really, small Schottky diodes in order to react faster than the gates for ESD protection.

So your feedback and input R must prevent this and meet all "ABS. MAX SPECS" under all conditions.

\$\endgroup\$
2
  • \$\begingroup\$ The input here is high impedance (which is why I need a buffer in the first place), so there should definitely be less than 5 mA of current. The feedback is 0Ω (because buffer), so the only voltage delta should be caused by the propagation delay. \$\endgroup\$
    – nsayer
    Commented Aug 31, 2021 at 2:56
  • \$\begingroup\$ Not quite. A transient load can cause non-linear glitches and the input impedance drops towards 100 Ohms (est. 500mV @5mA) when the diodes conduct at ABS MAX voltage limit. (Then lower Z when exceeded) So a series R is a MUST unless you can guarantee no ESD events etc. load flyback from inductance or surge current from load Capacitance, etc. Balanced R's also improve CMRR \$\endgroup\$
    – D.A.S.
    Commented Aug 31, 2021 at 3:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.