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SN65HVD1050: Vref pin Function

Lindsey Fike
Intellectual 2200 points
Part Number: SN65HVD1050
Other Parts Discussed in Thread: TCAN1051-Q1, TCAN1051V-Q1, TCAN1042-Q1

What would happen if the Vref pin (pin 5) of SN65HVD1050 were to be back-driven by 3.3V?  Since the functional block diagram doesn’t really indicate what the Vcc/2 structure is in the part, it’s hard to anticipate the effect.  Is it a high-impedance R divider? 

  • 0
    TI__Guru 62920 points

    Lindsey,

    It's a fairly high impedance output.  It is designed to range in voltage from 40% of VCC to 60% of VCC with a load current range of just -50 uA to +50 uA.  If you were to connect it to a 3.3-V source capable of sourcing much more than 50 uA, then you would easily over-drive this pin.

    While I wouldn't expect this condition to adversely affect the device, you may want to consider a newer transceiver that uses this pin as a "no connect" - see TCAN1051-Q1.  Or, you could use TCAN1051V-Q1 if you wanted this pin to be a power supply input used to set the TXD/RXD logic levels.

    Regards,
    Max

  • 0 in reply to Miguel Robertson
    TI__Intellectual 2200 points

    Hello Max, 

    Thanks for the quick feedback! I appreciate your suggestions. 

    Since my customer is asking for a product that is already in production I just wanted to clarify- if it’s a resistive structure, it should be okay in active modes but would we see any issues in standby? 


    Thanks!

  • 0 in reply to Lindsey Fike
    TI__Guru 62920 points

    Lindsey,

    The behavior of this pin is the same in both normal and silent modes.  (There isn't really a "standby" mode implemented on this chip like you would have in devices like SN65HVD1040A/TCAN1042-Q1.)

    Max