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Original question:

P82B715: how to use

P82B715: Usage also for level translation

Matthew Pediaditis
Prodigy 140 points
Part Number: P82B715
Other Parts Discussed in Thread: TCA9803, AFE4960P, SN74AXC4T774-Q1, TXU0104, TXU0304

Hi, I have a related question to the above case: Is this configuration possible, so the system can also act as level translating from 3.3V to 1.8V ?
Vcc_S1 = Vcc(Master) = Vcc_L = 3.3V
Vcc(Slave) = 3.3v
Vcc_S2 = 1.8V
Thanks!

  • 0
    Guru 263000 points

    At 3.3 V, the P82B715 does not run at full speed. But otherwise, it will work.

    If you want only level shifting, better use an actual level shifter like the TCA9803.

  • 0
    TI__Mastermind 27773 points

    Hi Matthew,

    Recommended operating conditions related to VCC = 3.3V will degrade performance as in making the device have longer rise and fall times which reduces overall i2c bus speed. 

    Do you need a buffer extender in application, or can you switch to a level shifter like Clemens has suggested already? 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 140 points

    Thank you Clemens and Tyler for your answers! We are currently using 2x P82B715 to connect an I2C sensor board (everything running at 3.3V) with an MCU board over a 60cm cable. The cable is the reason I chose the I2C extender. Although the length is not very big I decided to be on the safe side with the bus extender. Other GPIO signals and interrupts are passed through the cable using 2 buffers, one on each side (currently SN74AHC125RGYR) which also work fine. The new sensor board will now use one updated 1.8 V IO sensor (AFE4960P). So all IO will switch to 1.8V.

    Based on the experience with the buffers, and the fact that the cable is not very long, it seems to be ok to use 2X TCA9803 as Clemens suggested for I2C and translating buffers (e.g. SN74AXC4T774-Q1) for the other IO signals.

    Would you agree with that?

  • 0 in reply to Matthew Pediaditis
    Guru 263000 points

    60 cm isn't much; it might be possible to use a single TCA9803, just for level shifting.

    The TCA9803 has restrictions on what can be connected on its B side; see the datasheet.

    For unidirectional signals, consider using TXU translators (TXU0104, TXU0304, etc.).