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ISOM8110: Query Regarding PS2801C-1 Equivalent Product and Pin Pitch Compatibility

DDdoor
Expert 2435 points
Part Number: ISOM8110

Tool/software:

Hello,

What product corresponds to the PS2801C-1?

Additionally, in the cross-reference, the ISOM8110DFG is displayed as a drop-in replacement, but it seems that the pin pitch does not match.

Best regards,
DDdoor

  • 0
    Guru 317260 points

    The PS2801C-1 has a CTR between 50 % and 400 %; the ISOM8110 and ISM8111 are inside this range. (There are no exact matches for the narrower CTR ranks, but in most circuits, you can use an ISOM811x device with a higher CTR).

    The pin pitch indeed does not match. As far as I can see, the DFG package would be a replacement for the PS2501.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 29375 points

    Hello DDoor, 

    ISOM8110 corresponds most closely to PS2801C-1. As Clemens mentioned the package does not match. Also, ISOM8110 has a much tighter CTR range and will generally stay around the 120% typical value over temperature and lifetime which eliminates the need for overdesign that is required with normal opto-emulators. 

    Best,
    Andrew

  • 0 in reply to Andrew J
    Expert 2435 points

    Hello,

    Thank you for your replay.

    The fact that CTR is large means that you can obtain a large output current with a small input current, so I thought it was an advantage. Is that correct?

    Best regards,
    DDdoor

  • 0 in reply to DDdoor
    Guru 317260 points

    In most circuits, that is true.

    When the isolator is part of an analog feedback loop, increasing the CTR by a large factor might lead to instability.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 29375 points

    Hello DDoor,

    The key here is that an optocoupler with a high CTR is only advantageous if it is around its rated value with little variance. A optocoupler may have an extremely wide CTR range of 30% - 600% where the typical CTR is spec'd around 120%. This means that over lifetime, forward current and temperature the CTR can change dramatically and force the engineer to overdesign to compensate for the variation. This is why TI's opto-emulators are designed to have tight CTR ranges with little variance over lifetime and temperature. The opto-emulators are releasing in the CTR ranges shown below. 

    Best,
    Andrew