TCAN1044AV-Q1: Design value of suction current for CANH

Hi Naoki,

Is the device communicating at this time or just sitting recessive? What mode is the device in?

What does this test have to do with the performance of the device? CANH and CANL are output pins and applying 5V to these pins is just fighting the internal recessive biasing of the device. When this device is just sitting in normal mode in a recessive state it uses 4.5 mA so this value here has no bearing on the current consumption of the device. That is why I am confused as to what the purpose of this test is.

Best,

Chris

Hi Chris

Thanks for your reply.

The device is off state and it means no input power.

This test is requested by the customer and may be for checking a leackage current from signal pins when device is off.

I want to just clarify whether this current value is valid or not as the design concept.

Naoki,

This is not a test that we do for the reasons that I will talk about below. So I do not know if this is a valid value. I can potentially test this in our lab but currently we are very backed up and I don't have time right now.

Since these are output pins this is not a good test for leakage current. They are just measuring the impedance path through the output pins. The true measurement for "leakage" when this device is off is in the datasheet:

The true off state for this device is standby mode. When the device is in standby mode this is the current that the device consumes. This is a much better comparison to look at for other CAN devices because in actual operation this is the amount of current that the device needs to just exist in standby mode.

There would be no case where there is a leakage path from the CAN bus to ground because the driver is turned off in standby mode. The only time you would see 5V on the bus pins when the device is turned off is when another device is communicating with it. In that case the other device would be fighting the ground bias of the device in standby mode. It would also be using around 50 mA just to communicate a dominant pulse. Which makes the small 4.5 uA look like a rounding error. From a system level I don't think this test will give you much information.

Best,

Chris

Hi Chris

Thanks for your comment on this and I also agree with you.

Basically output pin should not be biased externally for measurement of leakage current.

But as I mentioned, this is the test requirement from the customer so we need to support the test as the current situation.

The point I just want to clarify is whether 4.5uA is valid value based on the design.

If ESD diode is an one of the answer, it should be O.K with us.

The current will not affect the system performance actually.

Is it possible to clarify it?

Clemens is correct,

The leakage current is specified for a maximum of 5 uA. Once again, I know we are on the same page, but I would like to reiterate that this is not a good measure of our performance compared to other competitor products. I just don't want the decision to go with our device or a competitor device to come down to the input leakage of our bus pins.

If you would like to talk about what other factors are important when it comes to a CAN transceivers performance I would be happy to go over that with you.

Best,

Chris