ISO1042: Schematic Review

Part Number: ISO1042
Other Parts Discussed in Thread: TCAN3414, , TCAN1044V

Tool/software:

Hello Team,

We are planning to use ISO1042BQDWRQ1 in our application. Please review the attached schematic.

We are using ATSAME51J19A controller. the controller side is 3V3 level compatible and another side is 5V compatible. But both the supplies are non-isolated from each other.

4 months ago

0 Clemens Ladisch 4 months ago

Guru 289110 points

If both grounds are actually the same, then you do not need an isolated transceiver.

There are transceivers with separate supplies for the I/Os, e.g., TCAN1044AV-Q1. There also are transceivers that run from only a 3.3 V supply, e.g., TCAN3414.

0 AP 4 months ago in reply to Clemens Ladisch

Prodigy 50 points

If we use same isolated transceiver without isolated ground, then is it OK?

0 Andrew J 4 months ago in reply to AP

TI__Mastermind 23005 points

Hello AP,

The isolated transceiver will function if the GND1 and GND2 are connected to the same grounds. However, as Clemens said, the application will not benefit from the isolation. To have full isolation performance, the ISO1042 needs to have both isolated powers and grounds.

There are non-isolated versions of the device that could be more relevant for your design if isolation is not needed.

Best,
Andrew

0 AP 4 months ago in reply to Andrew J

Prodigy 50 points

Is TCAN1044AV-Q1 has CANH and CANL are 5v compatible. Because in our application we required 5V compatible CANH and CANL signals.

0 Andrew J 4 months ago in reply to AP

TI__Mastermind 23005 points

Hello AP,

The TCAN1044AV-Q1 has two supply pins, VIO and VCC. VCC is the 5V supply for the CAN pins and VIO is the logic supply which allows for 3.3V compatibility on RXD and TXD.

0 AP 4 months ago in reply to Andrew J

Prodigy 50 points

Ok thanks. Can you suggest reference application design for this IC?

0 Andrew J 4 months ago in reply to AP

TI__Mastermind 23005 points

The best reference designs would be the EVM's and can be found on the product folder under design and development (TCAN1044AV-Q1). TIDM-02014 reference design | TI.com is also a reference design in the product folder.

0 AP 4 months ago in reply to Andrew J

Prodigy 50 points

Can we use same components (resistors, capacitors, inductors) as mentioned in above schematic for TCAN1044AV-Q1?

0 AP 4 months ago

Prodigy 50 points

Hello team,

Can we use TCAN1044VDDFR instead of TCAN1044AV-Q1 as we required full duplex communication?

0 Clemens Ladisch 4 months ago in reply to AP

Guru 289110 points

The transceiver itself needs decoupling capacitors at its supplies. The components connected to the CANH/CANL pins are the termination (only at the two ends of the bus) and protection components. What protection to use depends on what kind of noise and other voltage transients you expect.

You can use the same components as in your original schematic.

The TCAN1044V will work, but note that CAN always is half duplex.

0 AP 4 months ago in reply to Clemens Ladisch

Prodigy 50 points

OK. Thank You. But in the datasheet of TCAN1044V it is mentioned that it is a full duplex.

Can you please review the schematic? Is 0.1uF decoupling capacitor is sufficient for vcc and vio pin? Can we remove 1uF and 10uF capacitors?

I have one more doubt how to determine the impedance of differential line?

0 Andrew J 4 months ago in reply to AP

TI__Mastermind 23005 points

Hello AP,

CAN protocol is a half-duplex protocol since communication can only happen in one direction at a time. The TCAN1044V recommends only the 100nF decoupling capacitor as shown in 10 Power Supply Recommendations. However, the schematic should work as is.

Best,
Andrew

0 Eric Hackett 4 months ago in reply to Andrew J

TI__Guru 72372 points

AP,

I can confirm that the schematic will work as is:

The power rails are adequately decoupled.
CAN bus is properly filtered and protected.
TXD, RXD, and STB are all connected to a controller.

Regards,

Eric Hackett

0 AP 4 months ago in reply to Eric Hackett

Prodigy 50 points

OK. THANK YOU.

Isolation

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ISO1042: Schematic Review