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P82B96: 1.8V to 5V translation + signal quality enhancement

Antony Lin
Genius 13480 points
Part Number: P82B96
Other Parts Discussed in Thread: TCA9803, TCA9517

Hi,

We need a 1.8V to 3.3V I2C voltage translator including repeater function because there're several connecotrs on the signal path which degrade the signal.  Is P82B96 the best option for this application or there's a more economic option?

Thanks!

Antony

  • 0
    TI__Mastermind 49270 points

    Hey Antony,

    Some questions for you here:

    1) Can you tell me what is the max frequency the customer intends to use? (100kHz, 400kHz, 1MHz)

    2) Also you mention the signal is being degraded, do you know what is causing this (I assume too much capacitance)? A scope shot could be useful to make sure the signal integrity issue is due to capacitance.

    3) How much capacitance are they seeing on their I2C bus?

    4) Are they communicating over a cable or is this all onboard?

    ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    P82B96 is typically used in applications where I2C is needed across a long distance with cables. This device requires a minimum of two P82B96s (one on each side of the cable) For on board communication this device is usually a bit over the top as it isn't needed unless you expect a very large amount of capacitance on your I2C bus (this device buffers a max of 4000pF). If you expect something over 400pF (I2C standard for 400kHz) you could also just use multiple buffers in series to address the issue. (This sounds like the more economic option you were referring to)

    Currently I am thinking TCA980x (for something like 400pF TCA9803 would probably be the correct choice) or TCA9517. Both support 400kHz and also for level translation (TCA980x supports about 3.3V while TCA9517 is about 5V). You mention 1.8V to 3.3V in your first post but your title states 5V so I am unsure what you mean.

    If 1MHz is needed then TCA9617 is the only device we have that supports that frequency (it also provides voltage translation).

    Thanks,

    -Bobby