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Original question:

OPA2990: Amplifiers forum

OPA990: IS anyone reporting problems with this part, OPA990S in SOT23-6?

Clay Karmel
Prodigy 80 points
Part Number: OPA990
Other Parts Discussed in Thread: OPA170,

It seems as if the pinout may be wrong.  Our input to the + on pin 1 is being crushed (to 0V) when we enable the Op Amp (/SHDN goes low, which should be off, but their naming is wrong and low is 'on').

So we generate a PWM signal, R/C filter it and present to the + input on Pin 1.  Looks fine.  Then we enable the Op Amp and the input to Pin 1 is crushed to 0.  But nothing else connects to pin 1.  This is set up to be a follower (Op Amp output connected to - input).  So what is there to crush the input?

We notice that their similar part, OPA170, has a pinout for the "5 pin SOT" (which appears to actually be a SC-70), which is our same pinout (1 +, 2 V-, 3 -, 4 out, 5 V+) but their SOT 23 pinout is different (1 out, 2 V-, 3 +, 4 -, 5 V+). We're wondering if the OPA990S input pins might be 3 and 4 and not 1 and 3.  

  • 0
    Guru 140200 points

    Hi Clay ,

    do you have the latest datasheet from May 2020?

    I find this here:

    Kai

  • 0
    TI__Guru**** 154486 points

    Hello Clay,

    OPA990 in 5 pin DBV is released for a while so I trust that the pinout is correct. The May 2020 data sheet update should have fixed the negate symbol on the SHDN pins, but I see that did not get implemented.  SHDN is achieved by making the pin high (but do not exceed 20V). Low at SHDN makes the amplifier on.

    Based on the 5 pin DBV pinout, your empirical observation, and the table for OPA990S, output really is pin 1 on the OPA990SIDBVR. The table text is correct, but the image is not correct. This is the first report I have seen for that. I will see that both issues are corrected.

  • 0
    Prodigy 80 points

    So TI points out that the Table (on Page 4 of the data sheet) was correct, but the graphic (just above it on Page 4) was not, so my assumption of a pinout error was (sort of) correct.

    I have ordered a similar part, TLV9101SIDBVR because it matches the footprint I was expecting for the OPA990.  But, on closer inspection, no it does not.  The TLV9101SDBVRT has exactly the same error as the OPA990.  The graphic has output on pin 4.  The table has output on pin 1. 

    Oops.  Well, that's $100 in Digikey overnight/Saturday shipment fees wasted.  (I bought replacement OPA990S and then the TLV9101S.). Looks like some surgery on the PCB and a board spin.

    Suggest you fix both data sheets (both are wrong as of today, June 20, 2020).  Might want to check your other SOT23 Op Amps. At least on the TLV9101S the SHDN is correct.  On the OPA990 it is /SHDN, but 'low' is not shutdown, but 'on'.  HIGH is shutdown.  What's in a name, right?

  • 0 in reply to Clay Karmel
    Guru 140200 points

    Hi Clay,

    I find mistakes in datasheets very very annoying. Datasheets are the calling card of any electronic company. If I were the boss I would insist in correcting all the datasheets within a reasonable timescale. I wouldn't even tolerate the least mistake. And I would draw up a guide or tutorial on how to read and understand (!) a datasheet.

    Kai