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Controller area network bus driver and method for controlling driver

A driver and bus technology, applied in the field of controller area network bus transmitter

Active Publication Date: 2016-04-06
ANALOG DEVICES INT UNLTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This results in high common-mode load impedances that can be tens of kiloohms
Under these conditions, small fractional differences in the currents simultaneously conducted by PMOS transistor 16 and NMOS transistor 18 during on or off transitions can result in common-mode voltage fluctuations of one volt or more

Method used

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  • Controller area network bus driver and method for controlling driver
  • Controller area network bus driver and method for controlling driver
  • Controller area network bus driver and method for controlling driver

Examples

Experimental program
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Embodiment Construction

[0021] figure 2 A modified CAN bus driver 40 is illustrated, wherein elements equivalent to those in FIG. 1 are designated with the same numerals. The driver 40 further includes a pull-up source follower 42 and a pull-down source follower 44 .

[0022] Pull-up source follower 42 includes an NMOS transistor 46 whose drain is coupled to supply voltage Vcc and whose source is coupled to the source of PMOS transistor 48 which acts as a protective high voltage cascode device. The drain of PMOS transistor 48 is coupled to high-side bus line 20 . The gate of PMOS transistor 48 is coupled to system ground to turn it on, and the gate of NMOS transistor 46 is coupled to receive the control voltage generated by ramp generator 50 .

[0023] Pull-down source follower 44 includes a PMOS transistor 52 whose drain is coupled to system ground and whose source is coupled to the source of NMOS transistor 54 which acts as a protective high voltage cascode device. The drain of NMOS transistor ...

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PUM

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Abstract

The present invention relates to a controller area network bus driver and a method for controlling the driver. A Controller Area Network (CAN) driver (a transmitter) includes a conventional main driver having an open drain first driver MOSFET, for pulling up a first conductor of a bus in a dominant state, and an open drain second driver MOSFET, for pulling down a second conductor of the bus in the dominant state. Since it is difficult to perfectly match the driver MOSFET characteristics for conducting exactly equal currents during turning on and turning off, significant common mode fluctuations occur, resulting in electromagnetic emissions. Source followers are respectively connected in parallel with the first driver MOSFET and the second driver MOSFET for creating a low common mode loading impedance on the conductors during times when the main driver MOSFETs are turning on and turning off to greatly reduce any common mode fluctuations caused by the main driver MOSFETs.

Description

[0001] Cross References to Related Applications [0002] This application is based on and claims priority to U.S. Provisional Application No. 62 / 056,240, filed September 26, 2014, assigned by the inventor of the present invention to the assignee of the present invention and incorporated herein by reference . technical field [0003] The present invention relates to controller area network (CAN) bus transmitters and, in particular, to bus drivers that reduce common mode fluctuations. Background technique [0004] The Controller Area Network (CAN) bus standard ISO11898 was designed to allow devices to communicate with each other using a 2-wire bus. The ISO11898 standard is incorporated herein by reference. The data signals on the bus are differential, so any common-mode signals are ideally nullified. The standard is mainly applied to communication in vehicles, and examples of devices that can communicate on the bus include an engine control unit, power steering control uni...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L12/40
CPCH03K17/164H04L2012/40215H04L12/40032H03K17/687H03K3/012H04L12/12H04L12/40039
Inventor C·布伦南
Owner ANALOG DEVICES INT UNLTD