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SN65HVD234: How to measure RIN

Troyson Li
Expert 2505 points
Part Number: SN65HVD234

Hi TI team . 

        My customer used SN65HVD234 in their OBD product and needs the value of SN65HVD234 which should reply to upstream customer.They have removed the chip from PCB and allow the test condition(like the red block in the following picture) .But the value of  RIN they tested is  ∞ now .  So can you guide us how the test the RIN to obtain the reference value in specification? Thank you! 

 

  • 0
    TI__Guru 62920 points

    Hi Troyson,

    Since the device is powered and generating a recessive-level bias voltage, just using something like a multimeter wouldn't work (it would be tricked by the bias voltage into thinking the resistance is much higher).  Here's what you can do:

    1. Measure the voltage at CANH or CANL with nothing else connected to these pins ("VO_open").  It should be about 2.3 V.  Note that this bias voltage is applied to the bus via the RIN of the transceiver.

    2. Apply some test voltage ("V_test") through some test resistance ("R_test") to the pin.  Measure the new voltage appearing at CANH or CANL ("VO_test")

    3. You can now solve for the "RIN" of the transceiver using Kirchhoff's current law: (V_test - VO_test) / Rtest = (VO_test - VO_open) / RIN.

    Regards,
    Max

  • 0 in reply to Miguel Robertson
    Expert 2505 points

    Hi Max,

            Thank you ! We can test the correct value with your help .