MC33389 Ver la hoja de datos (PDF) - Motorola => Freescale

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MC33389

System Basis Chip with Low Speed Fault Tolerant CAN

Motorola => Freescale 

MC33389

FreescalDeEVSICEeDmESiCcRoIPnTIOdNuctor, Inc.

In the event of a permanent dominant TX state (for more

than 2ms) the output drivers are disabled. That assures the

operation of the complete system in case of a permanent

dominant TX state of one control unit. A defect control unit

autonomous go to RXOnly or TermVCC mode.

Low Power Modes

The transceiver provides a low power modes which can be

entered and exit by a SPI command. This is the BusStandby

mode with the lowest power consumption (for the

transceiver). CANL is biassed to the battery voltage via the

RTL output and the pull-up current source on CANL and pull-

down current source on CANH are disabled. Wake-up

requests are recognized by the transceiver, when a dominant

state is detected on either bus lines (Bus wake-up). On a Bus

wake-up request the SBC will activate the INTB output or, if it

is in sleep mode, switch to NormalRequest mode. This event

is stored in the WUISR status register.

To prevent false wake-up due to transients or RF fields,

wake-up threshold levels have to be maintained for a certain

time. In the transceiver low power mode, failure detection

circuit remains partly active to prevent increased power

consumption in cases of error 3, 4,7 and 8.

Power On

After the Vbat supply is switched on, the SBC is in

NormalRequest mode. The corresponding mode for the CAN

transceiver is BusStandby.

The CAN transceiver is supplied by V2. As long as V2 is

below its undervoltage threshold, the transceiver is forced to

BusStandby mode (fail safe property).

Protection

A current limiting circuit protects the transmitter output

stages against short-circuit to positive and negative battery

voltage. If the junction temperature exceeds a maximum

value, the transmitter output stages are disabled. Because the

transmitter is responsible for a part of the power dissipation,

this will result in a reduced power dissipation and hence a

lower chip temperature. All other parts of the transceiver will

remain operating. The CANH and CANL inputs are protected

against electrical transients which may occur in an automotive

environment.

Consequence Of Failure Detections

S1 is the switch from RTH to Ground

S2 is the switch from RTL to V2 and

S3 is the switch from RTL to Vbat

For each failure type is given which switch is open and

which driver is disabled.

Failure 1 : nothing done

Failure 2 : nothing done

Failure3 : S1 open. Driver CANH is disabled

Failure4 : S2 and S3 open. Driver CANL is disabled

Failure5 : Nothing done

Failure6 : S2 and S3 open. Driver CANL disabled

Failure7: S2 and S3 open. Driver CANL disabled

Failure8: S1 open. CANH driver disabled

Full transmitting and receiving capabilities are enabled.

Full failure detection is enabled.

Note: Standard/RXTX and Extended/RXTX are equivalent.

RXOnly mode

The transmitter is disabled but the receive part of the

transceiver remains active. In this mode, RX reports bus and

TX activity (RX = TX or Bus dominant).

Note: Standard/RXOnly and Extended/RXOnly are equivalent.

BusStandby Mode

This is the low power mode for the CAN transceiver. The

driver and receivers are disabled. Wake-up capability on both

bus lines as well as failure 3, 4, 7, 8 detection are enabled. In

bus standby mode RTL termination is set to Vbat.

Global Power Save Concept

The SBC allows to minimize power consumption of the

ECU. Several operating modes are available to go to low

power consumption when the full activity is not required.

Several possibilities are provided to wake-up the ECU. This

allows to have peripherals or the microcontroller switched off

when no activity on the ECU is required.

Two switchable independent supply voltages (V1 and V2)

are provided for optimum ECU power management.

Generalities

The SBC can be operated in four modes: Sleep, Standby,

Normal and Emergency mode. After reset, the MC33389 is

automatically initialised to a temporally mode, NormalRequest,

Waiting for microcontroller configuration.

Reset Mode

This mode is entered after SBC power up, or if an incorrect

Software W/D trigger occurs. The minimum duration for reset

mode is 1ms typical, and unless a V1 failure condition, the

SBC enters the NormalRequest mode after reset.

In case of V1 failure condition leading to V1 low (ex: short

to gnd), the SBC goes in reset mode. If V1 is still below reset

threshold after 100ms, the behavior depends upon the device

version A, C or D:

- A version : will enter sleep mode.

- C and D versions: will stay in reset mode.

NormalRequest Mode

This is the default mode after MC33389 reset. V1 is active,

V2 and V3 are passive. The SBC is not configured. The

default values are set in the registers. The SBC is waiting for

configuration data via the SPI.

If no SPI data is received 75ms after the Reset is released,

then the SBC switches itself to sleep mode.

The data the SBC must receive to consider that the

microcontroller starts the configuration sequence is the SW

timing word (in SWCR register). Once received this SW timing

word, the watchdog timer becomes active. Then any other

control data can be sent from the microcontroller to SBC.

The watchdog is not active in NormalRequest mode

before the SW timing word is programmed into the SBC. In

this mode, neither V2 nor the CAN transmitter are active.

CAN Transceiver Modes

The CAN transceiver has its own functioning modes:

RXTX mode, TermVBAT/TermVCC mode, and RXOnly mode.

They are controlled by TCR register.

RXTX mode

For More Information On This Product,

MC33389

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