TCAN1043A-Q1: CAN driving IC TCAN1043 strategy

Vishnu,

Are you referencing TCAN1043 or TCAN1043A? These are very different devices. In your schematic I see TCAN1043 so I will assume that. 

I see for your CANH and CANL lines that there is no common mode choke. Is this intended? A CMC is recommended for data rates over 500kHz. 

Ensure your ESD diode is close to the connector as possible. Otherwise, the schematic looks good. 

For the powerpoint, your strategy is correct except that a wake up CAN message receipt is not necessary as it will enter from Sleep to Normal mode with just nSTB=High and EN=High. 

Best,

Ethan

Hi Vishnu,

1. If you want the CAN message receipt to change the device from the sleep to normal mode, you will have to pass through Standby mode. Please reference the image I sent above of the state diagram. Keeping EN and nSTB always high will ignore the CAN bus and move to Normal mode automatically. 

My recommendation is to connect VIO to EN and nSTB. That way when the device is in Sleep mode, it will enter Standby mode from a CAN wake message. Once in Standby, INH is high, triggering the MCU to set VIO high. Because VIO is connected to EN and nSTB, it will move from Standby to Normal mode. 

2. Section 3 of the document below can help you pick a CMC. TCAN1043-Q1 can handle +/- 58V on the CANH/CANL bus so any part below the measured transient voltage will work. Specifically, Epcos B82789C0223 will work for your system. 

 https://www.ti.com/lit/an/slla271/slla271

Let me know if that helps or if you have any more questions.

Best,

Ethan

Vishnu,

This schematic looks good, although I noticed that the CMC is not placed. This might be intended, but I wanted to point this out. If you were to place it, it would go in between the transceiver and the termination resistors.

Additionally, I now noticed that the R1 and R2 termination resistors are DNF. Depending on the placement of the devices on the CAN bus, the two furthest end devices should have termination resistors. This ensures that the line is impedance matched at 60 Ohms. You might already be aware of this, but I wanted to highlight it. This thread details CAN termination well: e2e.ti.com/.../sn65hvd251-can-bus-termination

Best,

Ethan

Vishnu,

These modifications looks good.

The only minor comment I have is about the R2/R3 resistors used for termination. There are two ways to terminate the node: standard and split termination (preferred for cleaner bus signals). Initially you had it setup for split termination where you had two 60 Ohm resistors split by a 100nF capacitor to ground. I would recommend adding that capacitor back in to add that extra filtering, or I would recommend placing one resistor that is 120 Ohms instead of two resistors to save on cost. 

This document explains it in further detail: www.ti.com/.../SSZTB40

However, the design is still good as it currently stands. 

Best,

Ethan