MC33989(2002) 데이터 시트보기 (PDF) - Freescale Semiconductor

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MC33989
(Rev.:2002)

System Basis Chip with High Speed CAN Transceiver

Freescale Semiconductor 

MC33989

FreescalDeEVSICEeDmESiCcRoIPnTIOdNuctor, Inc.

Figure 3. Transient test pulses for CANH and CANL

1nF

CAN H

CAN L

1nF

Gnd

Transient Pulse

Generator

(note)

Gnd

note: Waveform in accordance to ISO7637 part1, test pulses 1, 2, 3a and 3b.

Figure 4. Transceiver AC characteristics

3.1

CAN error detection and wake up

The error and the wake up are reported in the CANR register.

3.1.1 Dominant State Time-out

This protection is based on the fact that all CAN signals can not have more than five bits in a row with the same state. In case

of a condition the Tx pin is stuck at 0v, the transceiver would hold the bus in dominant state making it impossible to the others

CAN modules to use the bus. The protection acts releasing the bus when a dominant signal with more than 350uS typical (Tdout

time) is present in the Tx signal. After entering the fault condition the driver is disabled. To clear this disabled state the CAN

transceiver needs to have its input going to recessive state.

3.1.2 Internal Error output flags

There are internal error flags to signals when one of the below condition happens. The errors are reported in CAN register.

• Thermal protection activated (bit THERM)

• Over Current detection in CANL or CANH pins (bit CUR).

• Time-out condition for dominant state (bit TXF).

3.1.3 Sleep mode & Wake-up via CAN bus feature

The HSCAN interface enters in a low consumption mode when the “CAN sleep mode” is enabled. In this mode the HSCAN

module will have a 60uA consumption via internal 5V.

When in sleep mode the transmitter and the receiver are disabled, the only part of circuit which remains working is the wake

up module which contains a special low power receiver to check the bus lines and according to its activity generate a wake up

output signal. The conditions for the wake is meet when there are 3 valid pulses in a row. A valid signal must have a pulse width

bigger than 0.5us and no more than 0.5ms.

For More Information On This Product,

MC33989

Go to: www.freescale.com

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