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TPS548A20: TPS548A20 connections for replacing the TPS549A20

Cosmin P
Intellectual 1640 points
Part Number: TPS548A20
Other Parts Discussed in Thread: TPS549A20

Hello,

Due o temporary shortages in the TPS549A20 availability, customer is considering using the TPS548A20 in the same location without actual layout change

Question is regarding the pins 27 and 28 - PMBus in 549A20 and recommended to be GND connected for the 548A20.

- Since these pins are ASIC driven for the PMBus version, is it acceptable for the ASIC to actively pull down these pins for the TPS548A20 instead of a straight GND connection?
- Is there an issue if these pins are pulled low by the ASIC with a delay (mseconds) after the the Vin power ramped up but before the TPS548A20 is enabled for conversion?

Thank you
Cosmin P.

  • +1
    TI__Genius 15547 points

    Hi Cosmin, 

    Our US team will check it and get back to you soon.

  • 0
    TI__Expert 8166 points

    The TPS549A20 and TPS548A20 are the same material up until the device is trimmed.

    Pin 27 and pin 28 are the test and trim interfaces for the devices.
    You can treat pin 27 and pin 28 on the TPS548A20 the same as the TPS549A20.

    If the pins on TPS548A20 can not be grounded, tying the pin high and disconnected from the bus is next best. The 27,28 pins could be connected to the I2C bus, but the device would ACK commands if you wrote an address associated with the Pin 1 RF.

    If pins 27 and 28 can not be grounded or tied high, floating pins 27 and 28 is an acceptable option. Pins 28 and 27 are open-drain based and require an external pull-up to raise the voltage on the lines to communication. When floating the pins, the ability to drive the pins 27 and 28 with the proper voltage levels, timing, and PMBus command format is minimal.