Controller area network (CAN) transmitter

Patent metadata

Field	Value
Publication number	US-12470427-B2
Application number	US-202318491886-A
Country	US
Kind code	B2
Filing date	Oct 23, 2023
Priority date	Oct 23, 2023
Publication date	Nov 11, 2025
Grant date	Nov 11, 2025

Abstract

A CAN transmitter includes an output branch, a replica branch including a replica of the output branch, and a feedback network. The output branch includes a first resistive element controlled by a first bias voltage and a second resistive element controlled by a second bias voltage. The replica branch has a feedback node that is replicated at a midpoint between the CANH bus terminal and the CANL bus terminal. The feedback network has a first input coupled to the feedback node, a second input configured to receive a midpoint reference voltage indicative of a desired midpoint voltage between the CANH and CANL terminals, and an output at which the first bias voltage is provided. A resistance controller is coupled to a control terminal of the second resistive element and configured to generate the second bias voltage based on a predetermined reference voltage and a bias current.

First claim

What is claimed is:

1 . A controller area network (CAN) transmitter for transmitting a signal comprising:
an output branch comprising a first resistive element coupled between a positive supply terminal and a first CAN bus terminal and controlled by a first bias voltage and a second resistive element coupled between a second CAN bus terminal and a negative supply terminal and controlled by a second bias voltage; a replica branch comprising a replica of the output branch and having a feedback node that is replicated at a midpoint between the first CAN bus terminal and the second CAN bus terminal; and a feedback network having a first input coupled to the feedback node, a second input configured to receive a midpoint reference voltage indicative of a desired midpoint voltage between the first CAN bus terminal and the second CAN bus terminal, and an output at which the first bias voltage is provided.

2 . The CAN transmitter of claim 1 wherein the replica branch comprises a scaled replica of the output branch.

3 . The CAN transmitter of claim 1 further comprising a resistance controller coupled to a control terminal of the second resistive element and configured to generate the second bias voltage based on a predetermined reference voltage and a bias current.

4 . The CAN transmitter of claim 3 wherein the resistance controller further comprises a temperature dependent current source.

5 . The CAN transmitter of claim 1 wherein the first resistive element comprises a p-type transistor and wherein the second resistive element comprises an n-type transistor.

6 . The CAN transmitter of claim 5 wherein each of the first resistive element and the second resistive element comprises a Field Effect Transistor (FET) or a bipolar transistor.

7 . The CAN transmitter of claim 1 wherein the output branch further comprises a switch element and a current limit element.

8 . The CAN transmitter of claim 7 wherein the switch element is coupled between the second CAN bus terminal and the second resistive element.

9 . The CAN transmitter of claim 1 wherein the output branch comprises a plurality of output branches coupled in parallel.

10 . The CAN transmitter of claim 1 wherein the output branch further comprises a first diode coupled between the first resistive element and the first CAN bus terminal and a second diode coupled between the second CAN bus terminal and the second resistive element.

11 . The CAN transmitter of claim 1 wherein one or both of the first resistive element or the second resistive element comprises a resistor coupled in parallel with the respective resistive element.

12 . The CAN transmitter of claim 1 wherein the CAN transmitter is configured for use in a gate driver and the transmitted signal is a gate drive signal.

13 . A method for transmitting a signal over a CAN bus having a first bus terminal coupled to a second bus terminal through a load resistor, comprising:
coupling a first resistive element between a positive supply terminal and the first bus terminal, wherein the first resistive element is controlled by a first bias voltage; coupling a second resistive element between the second bus terminal and negative supply terminal, wherein the second resistive element is controlled by a second bias voltage; and controlling the first resistive element with a feedback network having a first input coupled to a feedback node, a second input configured to receive a midpoint reference indicative of a desired midpoint voltage between the first CAN bus terminal and the second CAN bus terminal, and an output at which the first bias voltage is provided.

14 . The method of claim 13 further comprising providing a replicated first resistive element and a replicated second resistive element with a replica branch comprising the feedback node between the replicated first resistive element and the replicated second resistive element.

15 . The method of claim 14 wherein the first resistive element can have a size that is a multiple of the replicated first resistive element and wherein the second resistive element can have a size that is a multiple of the replicated second resistive element.

16 . The method of claim 13 further comprising controlling the second resistive element with a resistance controller coupled to a control terminal of the second resistive element and configured to generate the second bias voltage based on a predetermined reference voltage and a bias current.

Assignees

• Allegro Microsystems Llc

Inventors

• Ross Thomas
• Mcintosh James

Classifications

• H04B3/04 Primary

  Control of transmission; Equalising · CPC title

• H04L2012/40215

  Controller Area Network CAN · CPC title

• H04L12/40 Primary

  Bus networks · CPC title