MCZ33905S5EK Freescale Semiconductor, MCZ33905S5EK Datasheet - Page 53

• Manufacturer Part Number: MCZ33905S5EK
• Description: IC SYSTEM BASIS CHIP GEN2 32SOIC
• Manufacturer: Freescale Semiconductor

Specifications of MCZ33905S5EK

• Applications: System Basis Chip
• Interface: CAN, LIN
• Voltage - Supply: 5.5 V ~ 27 V
• Package / Case: 32-SOIC (7.5mm Width) Exposed Pad, 32-eSOIC, 32-HSOIC
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 8. Failure Detection Truth Table
DETECTION PRINCIPLE
shorted to GND, VDD (5.0 V), or VBAT, the voltage at the
other line follows the shorted line, due to the bus termination
resistance. For example: if CANL is shorted to GND, the
CANL voltage is zero, the CANH voltage measured by the Hg
comparator is also close to zero.
VBAT is possible. However, it is not possible with the above
implementation to distinguish which of the CANL or CANH
lines are shorted to GND or VBAT. A complete diagnostic is
possible once the driver is turned on, and in the dominant
state.
Number of Samples for Proper Failure Detection
recessive and dominant states to properly recognize the bus
failure. The error will be fully detected after five cycles of the
recessive-dominant states. As long as the failure detection
circuitry has not detected the same error for five recessive-
dominant cycles, the error is not reported.
BUS CLAMPING DETECTION
than (T
reported in the SPI.
Implementation for Detection
low to high transition of the differential receiver. Excluding the
internal propagation delay, the RXD output should be low
when the differential receiver is low. In case of an external
short to VDD at the RXD output, RXD will be tied to a high
Analog Integrated Circuit Device Data
Freescale Semiconductor
Failure Description
RXD
In the recessive state, if one of the two bus lines are
In the recessive state, the failure detection to GND or
The failure detector requires at least one cycle of the
If the bus is detected to be in dominant for a time longer
The implementation sense the RXD output voltage at each
CANH to 5.0 V
CANL to 5.0 V
No failure
TXD
DOM
V
V DD
DD
Diag
), the bus failure flag is set and the error is
/2
Rxsense
RxD driver
Logic
L5 (threshold V
Lg (threshold 1.75 V)
Figure 36. RxD Path Simplified Schematic, RxD Short to V
Diff
TxD driver
0
1
1
DD
Driver Recessive State
-0.43 V)
V
DD
CANH
CANL
The RxD flag is not the RXPR bit in the LPC register, and neither is the CANF in the INTR register.
H5 (threshold V
60
Hg (threshold 1.75 V)
CANL&H
RXD output
Prop delay
Diff output
RxD flag
0
1
1
DD
-0.43 V)
shorted to a high-voltage. In this case, current will flow from
the high-voltage short-circuit, through the bus termination
resistors (60 Ω), into the SPLIT pin (if used), and into the
device CANH and CANL input resistors, which are terminated
to internal 2.5 V biasing or to GND (Sleep mode).
of nodes, usage of the SPLIT pin, R
mode state (Sleep or Active) the voltage across the bus
termination can be sufficient to create a positive dominant
voltage between CANH and CANL, and the RXD pin will be
low. This would prevent start of any CAN communication, and
thus a proper failure identification (requires five pulses on
TXD). The bus dominant clamp circuit will help to determine
such failure situation.
RXD PERMANENT RECESSIVE FAILURE
hardware failure at the RxD output pin and ensure that a
permanent failure at RxD does not disturb the network
communication. If RxD is shorted to a logic high signal, the
CAN protocol module within the MCU will not recognize any
incoming message. In addition it will not be able to easily
distinguish the bus idle state and can start communication at
any time. In order to prevent this, an RxD failure detection is
necessary.
level and can be detected at the next low to high transition of
the differential receiver.
RXD driver is deactivated.
error is reported via SPI in CAN register.
Such condition could occur in case the CANH line is
Depending upon the high-voltage short-circuit, the number
The aim of this detection, is to diagnose an external
As soon as the RXD permanent recessive is detected, the
Once the error is detected the driver is disabled and the
L5 (threshold V
Sampling
Lg (threshold 1.75 V)
0
1
0
RxD short to V DD
DD
DD
-0.43 V)
Driver Dominant State
Detection
CAN BUS FAULT DIAGNOSTIC
Sampling
RxD flag latched
IN
H5 (threshold V
Hg (threshold 1.75 V)
actual resistor and
CAN INTERFACE
0
1
1
DD
-0.43 V)
33903/4/5
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