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Original question:

TPS23754: The difference of TPS23754 and TPS23754-1

TPS23754-1: Can the TPS23754-1 replace a TPS23754?

John Ford
Intellectual 510 points
Part Number: TPS23754-1
Other Parts Discussed in Thread: TPS23754,

Hi all.  We are in the middle of building 200 boards using the TPS23754, and it appears the part (and the 23756) is going to be unavailable for some time.  Our design has PPD tied to Vdd and Vdd1, and APD tied to RTN.  Can I drop in a 23754-1 and have the N/C pin connected to Vdd?  Or should I change the board and add a resistor to pull PPD to Vdd in case I use a 23754, and DNI the resistor if the part is a 23754-1?

Thanks.

John

  • +1
    TI__Mastermind 21320 points

    Hey John, 

    PPD enables a lower turn on threshold for the internal pass MOSFET. Connecting PPD to VDD enables classification to happen if APD is active. Since APD is always grounded, are you certain you are using PPD correctly? Do you intend to have a turn on voltage of 1.5V?

    PPD's intended use is to allow voltages lower than the PoE rang (37V-57V) to be used on the ethernet cable. 

    If so, the TPS23754-1 does not have PPD, it will  turn on in the normal PoE range (~42V). So you will have a different turn on threshold, I am not sure if that will work for your application? 42V and 1.5V turn on is very different performance. 

    Once the IC is on there is no other difference to the IC's. 

    If you are not intending to use PPD, the pin can be left floating and either IC will work. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    Intellectual 510 points

    Hi Michael.  We aren't using an auxilliary power source, so I guess we will rework the board to just leave the PPD pin floating for either part, since we want the normal PoE range.  I suppose I misread that data sheet.

    I was curious about the data sheet mentioning that the -1  "TPS23754-1 replaces the PPD pin with a no-connect for increased pin spacing." 

    It uses the same package, so I don't understand how this is helpful in increasing pin spacing?

    John