FUNCTIONAL DEVICE OPERATION
Table 8. V3 Control
CANH, RTL,RTH, RX, and TX pins are identical to the 33388,
stand alone CAN physical interface.
In Sleep Mode, During
Disable Time of Cyclic
Sense if Configured
—
The mode control for the CAN transceiver (Normal, VBAT
Stand-by, Sleep, etc.) are selectable through the 33389 SPI
interface.
—
—
—
Over Temp Threshold Reached
V1 Disabled (for any reason)
V2 Over Temperature Shutdown
• Baud Rate up to 125 kBit/s
• Supports unshielded bus wires
• Short-circuit proof to battery and ground in 12 V powered
systems
• Supports single-wire transmission modes with ground
offset voltages up to 1.5 V
• Automatic switching to single wire mode in case of bus
failures
• Automatic reset to differential mode if bus failure is
removed
Supply and VBAT Block
• VBAT Monitoring—VBAT is the main power supply coming
from the battery voltage after an external protection diode
(for reverse battery). VBAT is monitored for under voltage
and over voltage.
• VBAT Under Voltage—VBAT is monitored for under voltage
if it is below 4.0 V the BatFail flag is set in the VSSR
register and a maskable interrupt is sent to the
microcontroller.
• VBAT Over Voltage— When VBAT is > 20 V, the BatHigh
flag is set in the VSSR register. A maskable interrupt is
sent to the microcontroller. No specific action is taken to
reduce current consumption (to limit power dissipation).
This is to allow the entire flexibility to the microcontroller for
a decision.
• Low Electromagnetic Interference (EMI) due to built-in
slope control and signal symmetry
• Fully integrated receiver filters
• Thermally protected
• Bus lines protected against automotive transients
• Low current Bus Stand-by mode with wake-up capability
via the bus
• An unpowered node does not disturb the bus lines
CAN Transceiver
The device incorporates a low speed 125 kBaud CAN
physical interface. Its electrical parameters for the CANL,
BAT
V
DD
V
V
V
DD2
DD2 BAT
CAN_H
CAN_L
TX
RX
Protection
Transmitter
Drivers
Receiver
12.5k
S3
- Fail Detect
- Receive Mode
RTL
RTH
Termination
S2
RTL
CANH
CANL
RTH
CAN Transceiver Register
CAN transceiver simplified block diagram
SPI
S1
Figure 5. CAN Simplified Block Diagram
Failure4: S2 and S3 open. Driver CANL is disabled
Failure5: Nothing done
CONSEQUENCE OF FAILURE DETECTIONS
S1 is the switch from RTH to Ground
S2 is the switch from RTL to V2 and
Failure6: S2 and S3 open. Driver CANL disabled
Failure7: S2 and S3 open. Driver CANL disabled
S3 is the switch from RTL to VBAT
Each failure type provides data concerning which switch is
open and which driver is disabled.
Failure8: S1 Open. CANH driver disable
Failure 1: Nothing done
CAN Transceiver Description
Failure 2: Nothing done
The CAN transceiver is an interface between CAN
protocol controller and the physical bus. It is intended for low
Failure3: S1 open. Driver CANH is disabled
33389
Analog Integrated Circuit Device Data
Freescale Semiconductor
19
FREESCALE [ Freescale ]
