33742 datasheet(40/70 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33742

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

CAN SLEEP MODE

The 33742 offers two CAN Sleep modes:

• Sleep mode with CAN wake-up enable: detection of

incoming CAN message and SBC wake-up.

• Sleep mode with CAN wake-up disable: no detection of

incoming CAN message.

The CAN Sleep modes are set via the CAN SPI register.

In CAN Sleep mode (with wake-up enable or disable), the

CAN interface is internally supplied from the VSUP pin. The

voltage at V2 pin can be either 5.0V or turned off. When the

CAN is in Sleep mode, the current sourced from V2 is

extremely low. In most cases the V2 voltage is off; however,

the CAN can be placed into Sleep mode even with 5.0V

applied on V2.

In CAN Sleep mode, the CANH and CANL drivers are

disabled, and the receiver is also disabled. CANH and CANL

are high-impedance mode to ground.

CAN SIGNALS IN TXRX AND SLEEP MODES

When the CAN interface is set back into TXRX mode by an

SPI command, CAN H and CANL are set in recessive level.

This is illustrated in Figure 21.

Figure 21. CAN Signals in TXRX and Sleep Modes

CAN IN SLEEP MODE WITH WAKE-UP ENABLE

When the CAN interface is in Sleep mode with wake-up

enable, the CAN bus traffic is detected. The CAN bus wake-

up is a pattern wake-up.

PATTERN WAKE-UP

In order to wake up the CAN interface, the following criteria

must be fulfilled:

• The CAN interface wake-up receiver must receive a series

of three consecutive valid dominant pulses, each of which

must be longer than 500ns and shorter than 500

μs.

• The distance between 2 pulses must be lower than 500

μs.

• The three pulses must occur within a time frame of 1.0ms.

The pattern wake-up of the 33742 CAN interface allow

wake-up by any CAN message content.

Figure 22 below illustrates the CAN signals during a CAN

bus Sleep state and wake-up sequence.

CANL

CANH

TXD

RXD

Ground

2.5V

CANL Dominant

CANH Dominant

CANL/CANH Recessive

CAN in TXRX Mode

CAN in Sleep Mode

(Wake-up Enable or Disable)

CAN in TXRX Mode

(Controlled by SPI Command)

33742 Datasheet(PDF) 40 Page - Freescale Semiconductor, Inc

33742 Datasheet(HTML) 40 Page - Freescale Semiconductor, Inc

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