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TCAN1042GV-Q1: Input capacitance to ground (CANH or CANL)

Part Number: TCAN1042GV-Q1

Hi all,

We are testing TCAN1042GV-Q1 CI [Input capacitance to ground (CANH or CANL)].

Our Test Methodology:

1. RF coaxial cable with SMA connector mount to CAN_H and CAN_L.

2. Tested by Vector Network analyzer with 1-port calibration and port extension.

3. Connect DUT to VNA port-1.

3. Read capacitance values at Smith Chart mode.

And test results is 35 pF. [Spec. = 30 pF @MAX]

We would like to know why the test result doesn't meet spec. ? Or any advice for test methodology? 

Best regards,

  • User,

    The method used was pulled from the ISO11898-2:2003 specification. Since the specification requires a license, I can't share the specification or pages from it here.

    However, the idea is that a square waveform from 0-5V at 1kHz is injected into the CAN bus pins through a 10k series resistor. The signal is injected through the resistor into the CANH pin, in one case with the CANL pin shorted to GND, in the second case with CANL and CANH shorted together. You can then measure the tau of the edge and find the capacitance using the fomula T=RC for both cases. These values are then used to find the internal and differential capacitance.

    If you click my username you can find my email, and through that I can share some more detail.

    Please let me know if you have any other questions or concerns.

    Regards,