Data Sheet

8

Rev. 1.0, 2009-05-07

TLE6251-2G

Functional Description

The TLE6251-2G is a High Speed CAN transceiver, operating as an interface between the CAN controller and the

physical bus medium. A High Speed CAN network (abbreviated HS CAN) is a two wire differential network which

allows data transmission rates up to 1 MBaud. Characteristic for a HS CAN network are the two CAN bus states

“Dominant” and “Recessive” (see Figure 3).

A HS CAN network is a Carrier Sense Multiple Access network with Collision Detection. This means, every

participant of the CAN network is allowed to place its message on the same bus media simultaneously. This can

cause data collisions on the bus, which might corrupt the information content of the data stream. In order avoid

the loss of any information and to prioritize the messages, it is essential that the “Dominant” bus signal overrules

the “Recessive” bus signal.

The input TxD and the output RxD are connected to the microcontroller of the ECU. As shown in Figure 1, the

HS CAN transceiver TLE6251-2G has a receive unit and a output driver stage, allowing the transceiver to send

data to the bus medium and monitor the data from the bus medium at the same time. The HS CAN transceiver

TLE6251-2G converts the serial data stream available on the transmit data input TxD into a differential output

signal on CAN bus. The differential output signal is provided by the pins CANH and CANL. The receiver stage of

the TLE6251-2G monitors the data on the CAN bus and converts them to a serial data stream on the RxD pin. A

logical “Low” signal on the TxD pin creates a “Dominant” signal on the CAN bus, followed by a logical “Low” signal

on the RxD pin (see Figure 3). The feature, broadcasting data to the CAN bus and listening to the data traffic on

the CAN bus simultaneous is essential to support the bit to bit arbitration on CAN networks.

The voltage levels for a HS CAN on the bus medium are defined by the ISO 11898-2/-5 standards. If a data bit is

“Dominant” or “Recessive”, this depends on the voltage difference between CANH and CANL:

V

V

receive a “Recessive” signal from the CAN bus the differential signal

V

The voltage level on the digital input TxD and the digital output RxD is determined by the power supply level at the

pin

V

RxD) are compatible to microcontrollers with 5 V or 3.3 V I/O supply. Usually the

V

transceiver is connected to same power supply as I/O power supply of the microcontroller.

Partially supplied CAN networks are networks where the participants have a different power supply status. Some

nodes are powered up, other nodes are not powered, or some other nodes are in a Low - Power Mode, like Sleep

Mode for example. Regardless on the supply status of the HS CAN node, each participant which is connected to

the common bus, shall not disturb the communication on the bus media. The TLE6251-2G is designed to support

partially supplied networks. In power down status, the resistors of the Normal Receiver are switched off and the

bus input on the pins CANH and CANL is high resistive.