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TCAN4550-Q1: RECEIVER SWITCHING CHARACTERISTICS.

Kengo.Y
Guru 11165 points
Part Number: TCAN4550-Q1

Hi team,

My customer wants to use 500kHz for data transfer.

According to the datasheet, the Receiver switching characteristics is specified at 2,5,8MHz.


What should I think about at 500kHz?
If you have any advice, please let me know.

Please let me know if you have time to confirm the Dominant or Recessive.

Sincerely.
Kengo.

  • 0
    TI__Guru 53515 points

    Hi Kengo,

    This device can be configured to operate a variety of data rates depending on the bit-timing configuration and clock (or crystal) frequency. 2, 5, and 8 Mhz are simply example configurations that promote the device's use for high speed CAN operation. By configuring the bit-timing to be 4us based off the clock divisor and distribution of time quanta, an effective data rate of 250kbps (500kHz).

    The software user's guide for this device has a good overview of bit-timing configuration and how CAN controllers use divisors and time quanta to determine effective operating data rates. Let me know if you need help with the bit-timing configuration settings. 

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    Guru 11165 points

    Hi Eric,

    Thank you for your reply.

    Do you have MIN/MAX spec for the bit-timing at 500kHz?
    5 and 8MHz have MIN/MAX spec.

    And then, could you guarantee this spec?
    My customer wants to get the guarantee.

    Sincerely.
    Kengo.

  • +1 in reply to Kengo.Y
    TI__Guru 53515 points

    Hi Kengo,

    We don't have characterization data for this rate, but the bit timing symmetry will improve with lower data rates as the propagation delays from the device and bus become less significant in the larger overall bit time. If a value is needed for this spec, we can safely assume that these min/max values will be proportionally smaller than the timings at 2Mbps. 

    Data Rate MIN time MIN dev Ideal MAX time MAX dev
    2Mbps 435ns 13% 500ns 530ns 6%
    500kbps <1740ns* <13% 2000ns <2120ns* <6%

    *Keep in mind that we expect better performance than this in the same system because the delays do not scale the same with data rate and the effects of the bus will not be linear.  

    Because this is extrapolated data and not characterized, and most of the bit-width distortion at lower data rates will depend on bus characteristics, we can't guarantee this behavior. However, with all other things held constant, the relative bit width distortion will decrease when data rate decreases. 

    Let me know if this is sufficient for the customer. If not, please share what concerns they have about bit-width distortion at this slow data rate. If they are experiencing an issue, we may be able to address it from a system level.

    Regards,
    Eric Schott