TCAN1042V-Q1: TCAN1042V-Q1

Hi,

Can you provide a schematic of your set up? Are you able to take a scope shot of 4 signals at the same time? If so, can you take a scope shot of the VIO rail, STB pin transition, RXD, and CANH?

This device will assert the RXD pin in standby mode if it sees a WUP on the bus. However, this may not be the case since this device might already be in normal mode. Does this issue happen consistently every time you transition from normal to stand by? Is there any other device connected to the bus? Have you tried swapping out the device for another part and seeing if this issue still occurs?

Best,

Chris

Hi，Chris Ayoub：

    Here is the waveform of 4 signals at the same time.

and the figure below is the schematic ，in order to avoid the influence of External bus signals，CANH & CANL are floating 

Q： Does this issue happen consistently every time you transition from normal to stand by? 

A：NO！ it 100% happened when transit from standby to normal mode ；  see my Question1 above~

Q： Is there any other device connected to the bus?

A：No，there is no other device. 

Q： Have you tried swapping out the device for another part and seeing if this issue still occurs?

A：Yes， the issue happen again if i swap the TCAN1042 to a new device

I post  you a related link that is a case from an engineer（my fellow worker） who suffered the same problem 7 months ago

e2e.ti.com/.../tcan1042v-q1-question-about-rxd-pin-of-tcan1042vdrq1

thank you~

Before I can say whether that internal race condition is what is affecting the device let's make sure that it isn't a system issue first. Can you provide me another scope shot including the CANL and the CANH pin. Replace the VIO with CANL. Having the CANH and CANL floating could cause a momentary differential that is large enough to trigger the RXD to go low. Can you take a scope shot with 60 ohm termination and without 60 ohm termination. I am also looking at the differential between CANH and CANL so if you can zoom in on that transition where they initially become biased to 2.5V that would be great.

Best,

Chris

Hellp Chris：

    Here is the scope shot with 60 ohm termination

   and  this is a scope shot without termination below

 It is a certain probability problem, Not all chips of TCAN1042  have this problem.

Hi Jieming,

This is the internal race condition issue that your other co-worker faced. Another solution that I could suggest is using the TCAN1044A. This is a drop-in compatible device to the TCAN1042. This is a newer device meant to replace the TCAN1042 and it comes with better performance improvements over the TCAN1042 version.

I am going to check with design to make sure this was fixed.

Let me know what you think.

Best,

Chris

Hi，Chris：

    Thank you for your reply,  I appreciate it.