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SN65HVD234: Driver output voltages specified with 55R load rather than ISO specification 50R load.

Daniel Minors85
Prodigy 140 points
Part Number: SN65HVD234

Hi,

Reviewing the datasheet for the SN65HVD234 the bus output voltages are defined with a load specified in figure 12 & 14. This load appears to be 60Ohms+/-1% or 55Ohms +/-1% rather than as specified in ISO11898-2:2016 table 2 which defines the test condition to be RL = 50Ohms to 65Ohm.

Is there a reason why the tested load conditions were chosen for this test rather than the worst-case ISO spec loads, are they just typical values?

Also, there is no figure given on the datasheet for the Differential voltage on effective resistance during arbitration RL= 2240Ohms. Is compliance to the specification range 1.5V - 5V implied by the maximum loaded differential voltage and the fact that the supply rail of 3.3V limits the output to well under 5V?

Best Regards,

Dan

  • 0
    TI__Guru 65812 points

    Daniel,

    The 55-60 ohm test condition is meant to show results in a nominal condition, and what all CAN buses should aim to be for overall impedance. And for the figure, it's implied that the recessive level will fall within the required range in order to be interoperable with 5V transceivers. I've assigned an engineer on our applications to answer this question further, but it's also important to note that this family of devices were released prior to 2016. And while they should still adhere to most of the 2016 ISO11898 version, they are also 3.3V CAN transceivers, which will skew from some of the defined requirements purely because ISO11898 assumes a 5V supply rail.

    Regards,

    Eric Hackett