• TI Thinks Resolved

TSB41BA3B-EP: Differential Input Voltage Questions

Expert 4335 points

Replies: 4

Views: 83

Part Number: TSB41BA3B-EP


  • If we have the BMODE pin pulled low (deasserted), can we still have differential input voltages of 800mV?

From page 16 of the datasheet:

 Also, what is the maximum differential voltage that is allowed on the PHY before getting into performance and/or reliability concerns?

Thank you.


  • Your question came through Friday evening.  The engineer in charge of this device will respond when he gets back in on Monday morning.

  • BMODE affects only the interface to the link; page 3 of the datasheet says:

    The BMODE terminal does not select the cable interface mode of operation.

    The PHY will automatically detect whether the cable interface uses Alpha or Beta mode (see section 8.1.2 and annex O of IEEE1394-2008). Even with BMODE deasserted, it is allowed to connect to a Beta-capable node.

    The VIC/VID values are just copied from the specification. A standard-conforming transmitter will not generate higher differential voltages, so there is no need to test for those.

    Why are you asking this question? Do you want to ensure that nothing bad happens when connecting to a Beta node (it won't), or do you expect the PHY to be connected to something that is not an IEEE1394 transceiver?

  • In reply to Clemens Ladisch:

    Thanks for the information. However, can it handle more that 800mV? If so, what would be the maximum?

  • In reply to Roberto Arroyo Vazquez:


    The datasheet includes "absolute maximum ratings".  This defines the conditions to where significant stress can occur to the device.

    The Vin spec is -0.5v to Vdd + 0.5V (each signal treated as single ended).   If you stay within this range, then significant stress will not occur and device will not be damaged.

    However, correct operation of the device is only warranted when it is within the recommended operating conditions Ie, Vid < 800mV.

    If this answers your question, please click "This Resolved My Issue"