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TCAN1044-Q1: Quesetion about resistance between CAN_H and CAN_L

Chase Jeong
Mastermind 7645 points
Part Number: TCAN1044-Q1

Tool/software:

Dear TI experts,

My customer uses TCAN1044VDRQ1 for their new product.

Could you clarify the range of resistance value between CAN_H and CAN_L?

I cannot find clearly in the datasheet.

If there are differences between active state and idle state, please clarify both status.

Best regards,

Chase

  • 0
    TI__Guru 52166 points

    Hi Chase,

    Please see the RID and RIN specs. For differential, up to 90 kohms and half of that - 45 kohms for single ended, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    Mastermind 7645 points

    Dear Michael,

    Thank you for your support.

    My customer just want to measure the resistance between CAN_H and CAN_L without applying power source.

    actually they measured one device, the value was 69.3Kohm.

    Could you confirm that this value is in the range and still I can use the range of 40Kohm ~ 90Kohm in this measuring case?

    I am asking it because with no power source, I think this resistance value should have constant value, not wide range.

    Please check this issue. Thanks.

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Guru 52166 points

    Hi Chase,

    Yes, this is okay. 

    You can use the 40 k to 90 k as a powered device specification.  For unpowered checks, you may just verify that the device is not shorted (< 1 kohm) or open (> tens of Mohm), thanks. 

    Best Regards,

    Michael. 

  • 0 in reply to Michael Ikwuyum
    Mastermind 7645 points

    Dear Michael,

    Thank you for your support.

    69.3Kohm, the measured value from my customer is not in the range you said. Neither (<1kohm) nor (>tens of Mohm).

    I don't know how can I explain it to my customer.

    So here are my additional questions;

    1) I cannot see any resistors between CAN_L and CAN_H in block diagram. Is it true?

    2) Do you have any specification of resistance between CAN_H and CAN_L?

    3) Again, How can it be measured 69.3Kohm between CAN_H and CAN_L?

    4) Is it okay just not shorted? no specific range?

    Please check these issues. Thanks.

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Guru 52166 points

    Hi Chase,

    When 69 k is measured while unpowered, you are not seeing an actual designed in resistor. You are seeing a sum of all the internal protection and FET diode paths shown in figure 8-1, that the meter's tiny test voltage is biasing.

    1. No, no dedicated resistors when unpowered. See figure 8-3 clarifying.

    2. No, all the normal bias circuits are shut off and the bus pins go into a passive, very low leakage state when unpowered and any measured resistance is the sum of diode-leakage and FET paths.

    3. and 4. Yes, while unpowered, you should mainly verify for shorts < 1 K or open > 10 M. Anything between 10 K to 1 Mohms is normal leakage and you should not measure the true RID until VCC is applied, thanks.

    Best Regards,

    Michael.