MOTOROLA MC33388D Fault tolerant can interface Datasheet

Rev: 2.2 Date: 02 Nov 2000
MC33388
Advance Information
Fault Tolerant CAN Interface
The MC33388 is a CAN physical interface device, dedicated to
automotive body electronic multiplexing applications. It operates in
differential mode, allowing ground shifts up to 1,5V, reducing RFI
disturbances. It offers very low standby current in sleep and standby
mode operation and supports communication speeds up to 125kBauds.
It is fully protected against harsh automotive environments and the
driver is able to detect fault conditions and automatically switches into
appropriate default mode. Under fault condition, it continuously monitors
bus failures in order to switch back to normal bus operation as soon as
faults disappeared.
AUTOMOTIVE FAULT TOLERANT
CAN PHYSICAL LAYER
SEMICONDUCTOR
TECHNICAL DATA
• Very low sleep/standby current (15µA typical)
• Baud rate from 10 kBaud up to 125kBauds
• Automatic switching to single wire mode in case of bus failures and
return to differential mode if bus failures disappear
• Supports one wire transmission modes with ground offset up to 1.5V
• Internal bus driver slope control function to minimize RFI
• Bus line short-circuit protected to battery, VDD and ground
• Bus line protected against automotive transients
• Thermal protection of bus line drivers
• Supports unshielded twisted pair bus
• An unpowered node does not disturb the bus lines
• Wake-up capability triggered from bus message and wake-up input pin
• Wake up pin with dual edges sensitivity
• Battery fail flag reported on NERR output
• Ambient temperature range from -40°C to 125°C.
D SUFFIX
PLASTIC PACKAGE
CASE 751A-03
SO-14
PIN CONNECTIONS
Simplified Block Diagram
VDD
WAKE
EN
STB
INH
WAKE-UP LOGIC
MODE CONTROL
1
14
BAT
TX
2
13
GND
RX
3
12
CANL
NERR
4
11
CANH
STB
5
10
VDD
EN
6
9
RTL
WAKE
7
8
RTH
12.5k
VDD
PROTECTION
S5
S2
S3
(Top View)
RTL
SLOPE
CONTROL
&
DRIVER
TX
INH
BAT
CANH
CANL
RTH
S4
S1
NERR
FAILURE DETECTION
RECEIVER
RX
ORDERING INFORMATION
MUX
GND
Device
Operating
Temperature Range
MC33388D
TA = -40 to 125°C
Package
SO-14
MC33388
MAXIMUM RATING
Ratings
Symbol
Min
DC Supply Voltage Pin 10
VDD
DC Voltage On Pins 2, 3, 4, 5, 6 and 7
DC Voltage On Pins 11, 12
Transient Voltage At Pins 11, 12
0 < VDD < 5.5V ; V BAT≥ 0 ; T < 500ms
Transient Voltage On Pins 11, 12 (Coupled Through 1nF
Capacitor)
Typ
Max
Unit
-0.3
6
V
VDD
-0.3
VDD + 0.3
V
VBUS
-20
+27
V
VCANH/VCANL
-40
40
V
Vtr
-150
100
V
VBAT +0.3
V
DC Voltage On Pin 7
Vwake
Current In Pin 7
I wake
-15
3
mA
Vinh
-0.3
VBAT + 0.3
V
DC Voltage On Pins 8, 9
Vrtl, Vrth
-0.3
40
V
DC Voltage On Pins 14
VBAT
-0.3
27
V
Voltage On Pins 14 (Load Dump, 500ms)
VBAT
40
V
ESD Voltage On Any Pins (HBM.100pF ; 1.5kΩ)
VESD
-3.0
3.0
kV
ESD Voltage On Any Pins (MM.200pF ; 0Ω)
VESD
-200
200
V
Junction Temperature
Tj
-40
150
°C
Storage Temperature
Tstg
-55
150
°C
Rt
500
16000
Ω
Symbol
Value
Unit
Rth j/a
120
°C/W
Typ
Max
Unit
DC Voltage On Pins 1
RTH, RTL Termination Resistance
THERMAL RATINGS
Ratings
Thermal Resistance From Junction To Ambient
ELECTRICAL CHARACTERISTICS VDD = 4,75 to 5,25 ; VBAT=6 to 27V ; Tamb = -40 to 125°C unless otherwise specified
Conditions
Symbol
Min
SUPPLY
Vdd Supply Current (Normal Mode)
TX= VDD, Recessive State
IVDD
2.3
3
mA
Vdd Supply Current (Normal Mode)
TX = 0V, No Load, Dominant State
IVDD
3.3
5
mA
Vbat Supply Current (Normal Mode)
TX = VDD
IBAT
150
300
µA
Total Supply Current (Receive Only Mode)
VDD = 5V ; V BAT = 12V
IVDD + IBAT
0.85
1.2
mA
Total Supply Current (Vbat Standby Mode)
VDD = 5V ; V BAT = 12V
IVDD + IBAT
20
40
µA
IBAT
15
25
µA
Vbat Supply Current (Sleep Mode)
VDD = 0V ; V BAT = 12V
MC33388
MOTOROLA
2
MC33388
ELECTRICAL CHARACTERISTICS VDD = 4,75 to 5,25 ; VBAT=6 to 27V ; Tamb = -40 to 125°C unless otherwise specified
Conditions
Symbol
Min
Typ
Max
Unit
High Level Input Voltage
Vih
0.7*VDD
VDD+0.3V
V
Low Level Input Voltage
Vil
-0.3
0.3 * V DD
V
High Level Input Current (STB, EN) (V i = 4V)
Iih
40
µA
Low Level Input Current (STB, EN) (Vi = 1V)
Iil
10
20
TX High Level Input Current (Vi = 4V)
ITX
-25
-80
-200
µA
TX Low Level Input Current (Vi = 1V)
ITX
-100
-320
-800
µA
Forced V BAT Standby Mode (Fail Safe) Threshold
VDD
3
4
4.7
V
Battery Voltage For Setting Power On Flag
VBAT
1.5
3
4
V
High Level Output Voltage NERR (I0 = -100µA)
Voh
VDD - 0.9
VDD
V
High Level Output Voltage RX (I0 = -250µA)
Voh
VDD - 0.9
VDD
V
Low Level Output Voltage (I 0 = 1.5mA)
Vol
0
0.9
V
STB, EN, TX Pins
20
µA
RX, NERR Pins
WAKE Pin (must be connected to gnd or BAT if not used)
Typical Wake Up Threshold (VSTB = 0V), High to Low
Transition, VBAT=6V to 18V. NOTE1.
Wuthreshl
0.44 V BAT
V
Typical Wake Up Threshold (VSTB = 0V), Low To High
Transition, VBAT=6V to 18V. NOTE1.
Wuthreslh
0.57 V BAT
V
Wake Up Threshold Hysteresis
Wuhyst
500
mV
Wake Up Threshold, High to Low Transition at V BAT=12V
Wuhl
3.6
6.5
V
Wake Up Threshold, Low To High Transition at VBAT=12V
Wulh
6.2
7.5
V
High Level Voltage Drop (IINH = -0.2mA, INH High)
Vdrop
0
0.8
V
Leakage Current (Sleep Mode ; V INH = 0V)
Il inh
0
5
µA
Differential Receiver, Recessive To Dominant Threshold
(By Definition, V diff=VCANH-VCANL)
Vdiff1
-3.2
-2.5
V
Differential Receiver, Dominant To Recessive Threshold
(Bus Failures 1, 2, 5)
Vdiff2
-3.2
-2.5
V
0.2
V
INH Pin
CANH, CANL Pins
CANH Recessive Output Voltage
TX = VDD ; R (RTH) < 4k
VCANH
CANL Recessive Output Voltage
TX = VDD ; R (RTL) < 4k
VCANL
VDD - 0.2
V
CANH Output Voltage, Dominant
TX = 0V; I CANH = -40mA; Normal Operating Mode
VCANH
VDD - 1.4
V
MC33388
MOTOROLA
3
MC33388
ELECTRICAL CHARACTERISTICS VDD = 4,75 to 5,25 ; VBAT=6 to 27V ; Tamb = -40 to 125°C unless otherwise specified
Conditions
Symbol
Min
Typ
Max
Unit
1.4
V
CANL Output Voltage, Dominant
TX = 0V; I CANL = 40mA; Normal Operating Mode
VCANL
CANH Output Current (VCANH = 0 ; TX = 0)
ICANH
50
75
100
mA
CANL Output Current (VCANL = 14V; TX = 0)
ICANL
50
90
130
mA
Detection Threshold For Short-circuit To Battery Voltage
(Normal Mode)
VCANH, V CANL
7.3
7.9
8.9
V
Detection Threshold For Short-circuit To Battery Voltage
(Standby/Sleep Mode)
VCANH
VBAT/2 +3
VBAT /2+5
V
5
10
µA
0
2
µA
CANH Output Current (Sleep Mode; V CANH = 12V, Failure3)
CANL Output Current (Sleep Mode ; V CANL = 0V ;
VBAT = 12V, Failure 4)
ICANL
CANL Wake Up Voltage Threshold
Vwake,L
2.5
3.3
3.9
V
CANH Wake Up Voltage Threshold
Vwake,H
1.2
2
2.7
V
VwakeL-VwakeH
0.2
CANH Single Ended Receiver Threshold (Failures 4, 6, 7)
VSE, CANH
1.5
1.85
2.15
V
CANL Single Ended Receiver Threshold (Failures 3, 8)
VSE, CANL
2.8
3.05
3.4
V
CANL Pull Up Current (Normal Mode, Failures 4, 6 and 7)
ICANL,pu
45
75
90
µA
CANH Pull Down Current (Normal Mode, Failure 3)
ICANH,pd
45
75
90
µA
Receiver Differential Input Impedance CANH / CANL
Rdiff
100
180
kΩ
Differential Receiver Common Mode Voltage Range
Vcom
-10
10
V
Wake Up Threshold Difference (Hysteresis)
V
CANH To Ground Capacitance
CCANH
50
pF
CANL To Ground Capacitance
CCANL
50
pF
CCANL to C CANH Capacitor Difference (Absolute Value)
DCcan
10
pF
RTH, RTL Pins
RTL to VDD Switch On Resistance (I out < -10mA; Normal
Operating Mode)
Rrtl
10
30
50
Ω
RTL to BAT Switch Series Resistance (VBAT Standby Mode
Or Sleep Mode)
Rrtl
8
12.5
20
kΩ
RTH To Ground Switch On Resistance (I out <10mA; Normal
Operating Mode)
Rrth
10
25
50
Ω
Thermal Shutdown
Shutdown Temperature
MC33388
Tsd
MOTOROLA
165
°C
4
MC33388
AC CHARACTERISTICS VDD = 4,75 to 5,25 ; VBAT=6 to 27V ; Tamb = -40 to 125°C unless otherwise specified
CANL and CANH Slew Rates (10% to 90%).
Rising or Falling Edges. NOTE2.
Tsl
3.5
5
10
V/µs
Propagation Delay TX to RX Low. NOTE2.
Tpdlow
1
2
µs
Propagation Delay TX to RX High. NOTE2.
Tpdhigh
1
2
µs
Min. Dominant Time For Wake-up On CANL or CANH
(Vbat Standby And Sleep Modes ; V BAT = 12V)
Twake
8
16
30
µs
Min. WAKE Time For Wake-up
(Vbat Standby And Sleep Modes ; V BAT= 12V)
Twake
6
15
30
µs
Failure 3 Detection Time (Normal Mode)
Tdf3
10
60
µs
Failure 6 Detection Time (Normal Mode)
Tdf6
50
400
µs
Failure 3 Recovery Time (Normal Mode)
Tdr3
10
60
µs
Failure 6 Recovery Time (Normal Mode)
Tdr6
150
1000
µs
Failure 4, 7, 8 Detection Time (Normal Mode)
Tdf478
0.75
4
ms
Failure 4, 7, 8 Recovery Time (Normal Mode)
Tdr478
10
60
µs
Failure 3, 4, 7,8 Detection Time
(Vbat Standby And Sleep Modes ; V BAT = 12V)
Tdr347
0.8
8
ms
Failure 3, 4, 7,8 Recovery Time
(Vbat Standby And Sleep Modes ; V BAT = 12V)
Tdr347
2.5
ms
38
µs
0.75
4
ms
10
60
µs
Minimum Hold Time For “Go To Sleep” Command
Tgts
4
Edge Count Difference Between CANH and CANL for
Failures 1, 2, 5 Detection (NERR Becomes Low), (Normal Mode)
Ecdf
3
Edge Count Difference Between CANH And CANL For
Failures 1, 2, 5 Recovery (Normal Mode)
Ecdr
3
TX Permanent Dominant Timer Disable Time
(Normal Mode And Failure Mode)
tTX,d
TX Permanent Dominant Timer Enable Time
(Normal Mode And Failure Mode)
tTX,e
NOTE:
1. When VBAT is greater than 18V, the wake up thresholds remain identical to the wake up thresholds at 18V.
2. AC Characteristics measured according to schematic figure 2.
MC33388
MOTOROLA
5
MC33388
Figure 1. Device Signal Waveforms
Tx high: RECESSIVE Bit
Tx high: RECESSIVE Bit
VTX
Tx low: DOMINANT Bit
5V
CANL
3.6V
1.4V
0V
CANH
2.2V
Vth(dr)
0.7V
Vdiff
-2.9V
Vth(rd)
toffTX
-5V
VRX
0.7VCC
0.3VCC
tonRX
toffRX
t
RECESSIVE Bit
DOMINANT Bit
RECESSIVE Bit
Figure 2. Test Circuit For AC Characteristics
VDD
R
C
CANL
C
CANH
R
C
R = 100ohms
C = 1nF
MC33388
MOTOROLA
6
MC33388
DEVICE DESCRIPTION
Introduction
The MC33388 is a low speed CAN fault tolerant physical
interface designed for automotive multiplexed electronic
systems. The MC33388 addresses the low speed body
electronics application, in which the speed of communications
is between 10 and 125kBauds, on two wires bus
configurations. It is designed to operate in the harsh
automotive environment.
The MC33388 can control the external voltage regulator of
the system through the dedicated INH pin. It allows the
application to be switched into low power mode. Wake up can
be done either from bus activity or local wake up switch. The
MC33388 is tolerant to faults occurring at the CAN bus in
normal operating mode and low power mode.
Packaging
The device is assembled in a SO14 narrow body package.
Thermal performances allow the device to operate in the
automotive ambient temperature range, from –40°C to 125°C.
Transmitter Function
CAN bus levels are called Dominant and Recessive, and
correspond respectively to Low and High state of TX input pin.
The Recessive state is a weak state, where bus line are driven
through pull up and pull down resistors. Recessive state can
be over written by any other node forcing a Dominant state, in
which bus line are driven through active switches.
The bus is terminated by pull up and pull down resistors,
which are connected to GND, VDD or VBAT through
dedicated Rtl and Rth pins and internal circuitry.
The bus line slew rates are controlled in order to minimize
the RFI and this allows use of unshielded cables for the bus.
Receiver Function
In normal operation (no bus failures), RX is the image of
the differential bus voltage. The differential receiver inputs are
connected to CANH and CANL through integrated filters. The
filtered input signals are also used for the single wire
receivers.
The device incorporates comparators connected to CANH
and CANL in order to monitor and report the bus state to the
microcontroller as well as detect bus failures. Failures are
reported back to the microcontroller through NERR pin.
In normal operation when no failure is present the
differential comparator is active. Under fault condition, one of
the two CANH or CANL pin can be non operational then the
single ended comparator of either CANH or CANL is activated
and continue to report bus state to the microcontroller. The
MC33388 permanently monitors bus failure and recovery,
and as soon as fault disappears, it automatically switches
back to differential operation.
Noise Filtering
The device is optimized for dual wires operations. During
all single wire transmissions, the EMC performances in both
immunity and emission are worse than in differential mode.
Integrated receiver filters suppress any HF noise induced into
the bus wires. The cut-off frequency of these filters is a
compromise between propagation delay and HF suppression.
In single wire mode, low frequency noise can not be
distinguished from the active signal at the bus line.
MC33388
Device Operation Mode
The device has four operation modes : Normal, Receive
Only, Standby VBAT and Sleep. Each of these modes is
controlled by the state of EN and STB pins.
The state machine figure 3 and the truth table 1 indicate
how to configure the device into each mode and the pins
functions in each operation mode.
Operation Mode
Normal mode: In this mode, all functions are available and
NERR pin reports bus failure
Receive Only mode: In this mode, the transmitter path is
disabled, so the device do not drive the bus. It maintains
CANL and CANH in recessive state. The receiver function
operates normally. As the device can not drive the bus, an
incoming CAN message could not be acknowledge by the
node. NERR output signals the VBAT power-on flag and RX
reports bus state. Failure detection and management are the
same as in normal mode.
Sleep mode: In this mode, the transmitter and receiver
functions are disabled. CANL pin is connected to VBAT
through Rtl resistor and internal pull up resistor of 12.5kOhms.
INH pin is switched in high impedance state. The external
voltage regulator connected to INH will be switched off and no
VDD is supplied to MC33388. In this mode the device is still
supplied by the VBAT. Supply current from VBAT is 15uA
typical. The MC33388 monitors the bus activity and the state
of WAKE pin and VBAT level. If wake up conditions are
encountered, the device wakes up to Standby VBAT mode
and INH is switched on.
Standby VBAT mode: This mode is similar to Sleep mode,
but the INH pin is in high state in order to maintain the external
5V regulator activated. Wake up events are directly reported
to NERR and RX thanks to the 5V available at VDD. CANL is
in the same configuration as in Sleep mode.
Standby and Sleep modes are active when STB and EN
are low. Selection of Standby or Sleep is done through the
sequence of activation of EN and STB pins. Sleep mode is
entered through an intermediate steps (go to sleep) where
STB, EN are 0, 1. (Refer to truth table 1).
System Power On
When the supply is first applied to the system, VBAT and
VDD rise from zero up to their nominal value and the device
automatically enters into VBAT standby mode. At this time,
INH is switched in high state in order to activate the external
voltage regulator and an internal flag is set (batt fail flag). EN
and STB pins are internally forced in low state to maintain the
device into VBAT standby mode.
The VDD “forced Vbat standby mode (fail safe)” circuit will
maintain the device in VBAT standby mode until VDD is
higher that 3V, whatever the external state of EN and STB.
As soon as VDD reaches the “forced VBAT standby mode
(fail safe)” threshold, the device can enter into other mode,
depending upon EN and STB state.
VDD Reset Function
If during operation VDD drops below “forced VBAT standby
mode (fail safe)” threshold, the device is automatically switched
into VBAT standby mode to provide fail safe functionality.
MOTOROLA
7
MC33388
DEVICE DESCRIPTION
Battery Fail Flag
When the VBAT supply drops below “battery voltage for
setting power on flag” threshold, this information is internally
latched. This means that the system power supply has been
lost (disconnected and reconnected for instance).
This flag can be read by the microcontroller by switching
the device into receive only mode, where NERR pin reports
the VBAT power on flag. This flag is reset by entering into the
Normal mode.
Bus Failure Detection
The device permanently monitors the bus lines and
detects faults in normal and receive only modes. Below is the
list of failures detected at the bus level :
1- CANH wire interruption
2- CANL wire interruption
3- CANH short-circuit to battery
4- CANL short-circuit to ground
5- CANH short-circuit to ground
6- CANL short-circuit to battery
7- CANL and CAN H mutually shorted
8- CANH short-circuit to Vdd
TX Permanent Dominant Detection
In addition to the above list, the MC33388 detects a
permanent low state at TX input which results of a permanent
dominant bus state. The MC33388 detects if TX is Low for
more than 2ms typical and then disables the bus output driver
in order to switch into recessive state. This avoid to block
communication between other nodes of the network.
Behaviour Under Faults Condition
When a fault is detected, the device automatically takes
appropriate action to minimize the system current
consumption and to allow communication on the network.
Depending on the type of fault, the mode of operation and the
fault detected, the device automatically switches off one or
more of the following functions: CANL or CANH line driver, Rtl
or Rth pull up or down resistors or internal switches. These
actions are detailed in table 2.
The device permanently monitors the faults and in case of
fault recovery, it automatically switches back to normal
operation and reconnects the open functions. Faults detection
and recovery circuitry have internal filters and delays timing
detailed in the AC characteristics parameters section.
Detailed Description of Error Detections
The differential receiver threshold is set at -2,8V. This
assures a proper reception in the normal operating modes
and in case of failures 1, 2 and 5 noise margin as high as
possible. These failures or their recovery do not destroy
ongoing transmissions.
MC33388
Failures 3 and 6 are detected by comparators respectively
connected to CANH and CANL. If the comparator threshold is
exceeded for a certain time, the device is switched to single
wire mode. This time is needed to avoid false triggering by
external RF fields. Recovery from these failures is detected
automatically after a certain time-out (filtering) and no
transmission is lost.
Failures 4, 7 and 8 initially result in a permanent dominant
level at the internal comparator outputs. If failure 4 and 7
appear, the CANL driver and the RTL pin are switched off
after a time out, only a weak pull up at RTL remains.
Reception continues by switching to single wire mode through
CANH. When the failures 4 or 7 are removed, the recessive
bus levels are restored. If the receiver voltages remain in the
recessive state for a certain time, reception and transmission
switch back to the differential mode.
If failure 8 is recognized, the CANH driver is switched off
after a time out and the reception is switched to single wire
mode through CANL. If the receiver voltages remain in the
recessive state for a certain time, reception and transmission
switch back automatically to the differential mode.
If any of the 8 wiring failure occurs, the output NERR will
be switched low. When the error recovers, NERR will be
switched back to high state.
Wake Up Events
Wake-up requests are recognized by the MC33388 in
Sleep or VBAT Stanby modes, either when a dominant state
is detected on CANL or CANH bus lines (remote wake-up) or
if the WAKE pin changes state (local wake-up).
Under power-up conditions when VBAT is higher than 5V,
the state voltage on the WAKE pin is considered to be the
reference state for the wake-up function. On leaving normal
mode, the current WAKE pin state becomes the new
reference state.
In sleep mode, on a wake-up request the transceiver sets
the INH output high, to activate the external voltage regulator,
used for VDD supplied. In VBAT standby INH is already set
high. When VDD is set, the wake-up request can be read on
the NERR or RX outputs by the microcontroller.
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 low power modes, failure detection circuit remains
partly active to prevent increased power consumption in
cases of error 3, 4, 7 and 8.
Fault Operation Table
Table 2 shows the device operation in normal and low
power modes and the internal actions happening under fault
condition. Please refer to simplified block diagram page 1 for
device internal switch reference.
MOTOROLA
8
MC33388
DEVICE DESCRIPTION
Figure 3. State Machine And Operation Modes
Normal mode (1, 1)
(0, 1)
Go to sleep mode (0, 1)
(BUS failure, ON)
(1, 1)
(Wake up event, OFF3)
(0, 0)
(1, 1)
(1, 1)
(1, 1)1
(1, 0)
Sleep mode (0, 0)
(0, 0)
(1, 0)
(1, 0)1
(0, 0)4
(Wake up event1,2, OFF)
(0, 1)
(0, 1)
wake-up event
(bus message, wake pin)
Receive Only mode (1, 0)
(0, 0)
Stand-by VBAT mode (0, 0)
(VBAT fail flag, ON)
(1, 0)
(Wake up event, ON)
power up
Legend:
Transceiver mode (STB state, EN state)
(NERR function, INH state)
NERR: BUS - Bus error is flagged
WAKE - Wake-up event is flagged
BAT - BAT fail is flagged
1
with permanent VDD
2
VDD is still switched on
3
if no wake-up occurs after 25µs
4
as long as INH is on
INH: ON - INH is switched on
OFF - INH is floating
Table 1 • Truth Table
STB
EN
Mode
INH
0
0
VBAT
Standby1
High
0
0
Sleep2
Floating
0
1
Go to sleep
command
Floating
1
0
Receive Only3
High
1
1
Normal
High
NERR
RX
Active LOW:
wake-up interrupt signal
(if V DD is present)
RTL
IDD (4)
IBAT (4)
Switched to
VBAT
5µA
typ. 15µA
Switched to
VBAT
Not
applicable
typ. 15µA
Switched to
VBAT
Active LOW:
VBAT power-on flag
High: recessive state
Low: dominant state
Active LOW:
error flag
Switched to
VDD
800µA
Switched to
VDD
2.3mA (5)
3.3mA (6)
typ.
150µA
NOTES:
1. Wake-up interrupts are released when entering normal operating mode.
2. If go to sleep command was used before (EN may turn LOW as VDD drops, without affecting internal functions because of fail safe functionality.
3. VBAT power-on flag will be reset when entering normal operation mode.
4. Value are typical, without bus load current.
5. In recessive state.
6. In Dominant State, value with no load at bus.
MC33388
MOTOROLA
9
MC33388
DEVICE DESCRIPTION
Table 2 • Detail Fault Operation Table
Mode
State of S1, S2, S3 Internal Switches and CANL CANH Output
Drivers (Ref to Normal Mode)
No failure
Normal and
receive only
S1, S2 closed, CANL, CANH drivers enabled
No failure
VBAT standby
S3 closed, CANL, CANH drivers disabled
No failure
Sleep mode
S3 closed, CANL, CANH drivers disabled
Failure #
Description
1
CANH wire interrupted
Normal and
receive only
CANL, CANH drivers enabled, S1, S2 closed
2
CANL wire interrupted
Normal and
receive only
CANL, CANH drivers enabled
S1, S2 closed
3
CANH short to BAT
All
S1 open, CANH driver disabled
4
CANL short to GND
All
S2, S3 open & CANL driver disabled
5
CANH short to GND
Normal and
receive only
CANL, CANH drivers enabled
S1, S2 closed
6
CANL short to BAT
Normal and
receive only
S2, S3 open & CANL driver disabled
7
CANL short to CANH
All
S2, S3 open & CANL driver disabled
8
CANH short to VDD
All
S1 open, CANH driver disabled
NOTE: S4 and S5 behaviours are only dependant upon the device operating mode.
S4 and S5 switches are closed in normal and receive only modes and are open in sleep and standby modes.
MC33388
MOTOROLA
10
MC33388
PIN FUNCTION DESCRIPTION
VBAT (input) : This is the supply line of the device. It can
be directly connected to the battery line, can operate up to
27VDC and sustains up to 40V during load dump condition.
The supply current is dependant upon the device operation
mode. In low power mode, it is as low as 12uA typical. A
battery fail flag circuitry is associated to this pin.
The Vbat pin must be protected by external component
against reverse battery and negative transient voltages.
VDD (input) : 5V input supply voltage for the device. In
normal mode, the current is up to 5mA typical and do not
exceed few uA in Vbat standby mode. An under voltage
function is associated to Vdd and resets the device to Vbat
standby mode when Vdd falls below 3V.
CANH : Bus output driver pin. CANH is a high side switch
structure connected to VDD supply. In recessive state, the
high side switch is off and bus CANH line is biassed through
the Rth pin circuitry and external Rth resistor. In dominant
state, high side switch is on and CANH line is switched to
VDD. Output voltage is above 3.6V. CANH output is protected
against short-circuit to ground, by internal current limitation. A
thermal shutdown with hysteresis switches off CANH driver if
temperature rises above 150°C. CANH is also protected
against short-circuit to higher voltage, such as VBAT by an
internal serial diode in series with the switching component.
CANH has a pull down current source, typically 75uA, which
can be activated under some fault condition.
Rth : Connection to the CANH bus terminal resistors. Rth
output structure is a low side switch, turned on under normal
condition and automatically desactivated under some fault
condition. In the application, an external resistor is connected between Rth and CANH pins. In recessive state
when CANH driver is off, CANH line is tied to ground through
the external Rth resistor.
CANL : Bus output driver pin. CANL is a low side switch
structure to the ground. In recessive state, the low side switch
is off, and bus CANL line is biassed through the Rtl circuitry
and external Rtl resistor. In dominant state, low side switch is
on and CANL line is switched to ground. Output voltage is
below 1.4V. CANL output is protected against short-circuit to
VBAT, by internal current limitation. A thermal shutdown with
hysteresis is integrated and switches off CANL driver if
temperature rises above 150°C. CANL is protected against
negative voltage, by an internal serial diode in series with the
switching component. CANL has a pull up current source,
typically 75uA, activated under some fault condition.
Rtl : Connection to the CANL bus terminal resistors. Rtl
output structure is a low side switch, turned on under normal
condition and automatically desactivated under some fault
condition. In the application, an external resistor is connected
between Rtl and CANL pins. In recessive state when CANL
driver is off, CANL line is tied to VDD through external Rtl
resistor.
In VBAT Standby and Sleep modes, Rtl pin is connected
to the VBAT line through an internal switch and a 12.5kΩ
resistor. This means that in these modes CANL bus line is
biassed to VBAT. Wake up from these modes are detected by
CANL line going from VBAT level to CANL wake up threshold
level.
MC33388
STB and EN : Input pins used to configure the device into
desired mode. These pins are CMOS compatible and are
connected to the microcontroller of the application.
INH : This is an output of the MC33388 used to control an
external voltage regulator having an inhibit input. INH is a high
side switch structure, active when the MC33388 is in normal,
Receive only or Standby VBAT modes. INH is switched off in
Sleep mode to switch off the voltage regulator of the
application. INH has no pull down structure.
WAKE : This is a high voltage input used to wake up the
device from Sleep and VBAT Standby modes. Wake is
usually connected to an external switch in the application. The
typical wake thresholds are Vbat/2.
Wake pin has special design structure and allows wake up
from both high to low or low to high transitions. When entering
into the Sleep or VBAT Standby mode, the MC33388
monitors the state of the wake pin and stores it as reference
state. The opposite state of this reference state will be the
wake up event used by the device to enter again into normal
mode.
An internal filter is implemented, with 8 to 38 µs filtering
time delay. Wake pin input structure exhibits a high
impedance, with extremely low input current. A serial resistor
should be inserted in order to limit the input current mainly
during transient pulses.
CAUTION : The Wake pin should not be left open. If wake
up function is not used, wake should be connected to GND to
avoid false wake up.
TX : Transmitter input pin to control bus state. It is CMOS
compatible and usually directly connected to the TX output of
a microcontroller. When TX is at high state, CANH and CANL
are in recessive state. When TX is low, CANL and CANH are
in dominant state. Special fault handling is provided to this
input, in order to detect permanent dominant state (TX low)
which would result of CAN bus permanently lock in dominant
state and do not allow communication. In case where TX is
low for more than 2ms typical, the device automatically
switches the bus lines to recessive. TX has an internal pull up
resistor to VDD.
RX : Output receiver connection to the microcontroller. It
reports the bus state to the RX input pin of the microcontroller.
RX is high when bus is recessive and low in dominant state. In
sleep and standby Vbat modes, RX reports wake up events.
NERR : Error output pin which reports errors encountered
by the device. When NERR is high, no error is reported, when
NERR is low an error has been detected. In Standby VBAT
mode NERR reports a wake up event. In receive only mode,
NERR reports VBAT power on flag.
Table 3 • Truth Table of RX, TX CAN Bus States
TX
RX
Bus States
Low
Low
Dominant
High
High
Recessive
High
Low
Dominant
MOTOROLA
Comment
Bus Driven By Other Node
11
MC33388
APPLICATION
Table 4 • Typical Application Schematic
BATTERY
BATTERY
IC1
5V
Switch
D1
R4
C2
12V
R4
Switch
C3
C4
WAKE
INH
VDD
RTH
C1
Vdd
option with switch to gnd
R3
VBAT
R1
L1
CANH
EN
MCU
CAN BUS
I/O
Port
STB
CANL
NERR
R2
TX
CAN
RTL
MODULE
RX
GND
MC33388D
Vss
R3
Figure 4 above is the typical application schematic. All
MC33388 capabilities are utilized : CAN interface, normal
and low power modes, wake up source from CAN bus or
wake up switch.
The MC33388 VDD is supplied through an external
voltage regulator having an inhibit input pin. In addition to TX
and RX connections to the microcontroller CAN module, the
MC33388 requires 3 additional connections to a standard
microcontroller I/O port for EN, STB and NERR pins.
MC33388 wake pin is connected to an external signal
switch. MC33388 allows the signal switch configuration to be
either connected to Vbat or to ground through pull up or pull
down resistor. Solution with switch to GND is indicated as
option in the application schematic. A resistor must be
inserted in series with wake pin in order to limit the input
current during positive and negative transient pulses.
De-coupling capacitors are recommended on the
MC33388 VBAT and VDD lines. Those capacitors might be
shared with other devices from the same printed circuit
board, depending on its configuration.
R1 and R2 are the network termination resistors. For
proper operation, they must have identical value (R1 equals
Component information:
R3: 10kΩ
R4: >= 33kΩ
C1>= 47nF
C2>= 4.7uF
C3>= 47nF
C4>= 10uF
L1: optional common mode choke
D1: 1N4148
IC1: LM2935
R1=R2=R (500Ω<R<16kΩ)
R/number of nodes>100Ω
to R2). Their value is determined by the total network
termination resistor and the number of nodes.
The total network termination resistor value must be
higher than 100Ω. If a 500Ω termination resistor is chosen,
with a system composed of 32 nodes, each R1 or R2 will be
16kΩ. In addition, R1 and R2 values should be chosen
between 500Ω and 16kΩ at each node.
The CANH and CANL pin can be directly connected to the
CAN bus. A serial common mode inductance can be inserted
in order to improve electromagnetic compatibility
performances both in emission and susceptibility.
Minimum Application Configuration
The minimum device configuration is described in
minimum application schematic figure 5 below. The device is
used as CAN transceiver only and other features are not used.
The device EN and STB input pins must be connected to 5V in
order to set the device in normal mode. INH and NERR can be
left open.
CAUTION : WAKE should not be left open and must be
connected to a known state, i.e GND.
Figure 4. Minimum Application Schematic
BATTERY
D1
C3
C4
5V
C2
INH
VBAT
RTH
VDD
Vdd
C1
EN
R1
STB
MCU
WAKE
CANH
CAN BUS
NERR
Component information:
C1>= 47nF
C2>= 4.7uF
C3>= 47nF
C4>= 10uF
D1: 1N4148
R1=R2=R (500Ω<R<16kΩ)
R / number of nodes>100Ω
CANL
R2
CAN
MODULE
Vss
MC33388
TX
RTL
RX
MC33388D
GND
MOTOROLA
12
MC33388
Electromagnetic Compatibility
Introduction
The device is designed for optimized noise emission (EMI)
and high susceptibility performances (EMC). The source for
both disturbance and susceptibility is primarily coming form the
bus line wires. They are by far the longest connections
compared to the printed circuit board of the application
receiving the MC333388, the microcontroller and the other
components.
CAUTION : The common mode voltage characteristics are
dependant upon immediate device environment, such as bus
capacitor loading, bus wire length and type, etc... In addition, the
symmetry of the CANL and CANH bus lines is key parameter to
optimize common mode glitches. For instance un-symmetry
could result in different parasitic capacitors value between
CANL to GND and CANH to GND and will increase common
mode glitches and degrade overall system performances.
EMI Noise
In order to minimize the HF noise generated by the
complete application, the MC33388 minimizes the common
mode voltage and current glitches occurring at each bus
transition : from dominant to recessive and from recessive to
dominant. This is achieves by excellent matching in signal
transition between CANL and CANH. The common mode
voltage and current glitches are defined as follow :
CmV = (Vcanh+Vcanl)/2,
CmI = (Icanh+Icanl)/2.
The device is optimized for dual wires operations. Under a
fault condition, for instance one CAN bus connection shorted to
fixed voltage, e.g GND, the common mode will be considerably
degraded.
Figure below shows the typical signals for common mode
voltage measured at CANL and CANH pins.
EMC Susceptibility Performances
The MC33388 is optimized for high immunity from external
field disturbances. The bus lines are by far the primary antenna
for external field coupling to the CANL, CANH, Rtl and Rth
connections. The device performances are characterized using
the Bulk Current Injection (BCI) test method, derivated from
specification ISO 11452-4.
Susceptibility evaluation with BCI :
The component is configured according to the electrical
schematic very close to the typical application schematic, figure
4. Main difference is that the microcontroller is replaced by an
external generator and analyzer connected to RX, TX and
NERR through optical link. A network composed of two nodes
equipped with MC33388, one in emitter and one in receiver is
evaluated. The disturbance is applied to both CANL and CANH
twisted pair bus line lines with appropriate coupling clamp.
During test sequences, received bits are compared to
transmit bits. When received bits are different from transmit bits
the device is considered as fail for the particular frequency.
Figure 5. Typical Common Mode Glitch
Measured at CANL CANH
Results
Figures 7 and 8 below describe the device susceptibility
performances in the frequency range of 1 to 400MHz with target
of injected current of 200mA and 316mA.
When the target current is reached and when no
susceptibility is observed, the next frequency point is analyzed,
until reaching the max frequency, 400Mhz. If a susceptibility is
observed for a particular frequency, the free point is marked.
Figure 7 below shows results with a target susceptibility level
of 316mA or 49dBmA with a 1KHz 80% modulation added to the
injected current. Figure 8 shows the susceptibility levels with a
target susceptibility level of 200mA or 46dBmA without
modulation added to the injected current.
NERR: 5V/div
Common Mode
Glitch
100mV/div
Tx: 5V/div
Figure 7. Min. Susceptibility Level Without Modulation
Figure 6. Min. Susceptibility Level With Modulation
60
60
LIMIT OF TEST (46dB) (No Susceptibility)
LIMIT OF TEST (49dB) (No Susceptibility)
40
Susceptibility Points
30
NO SUSCEPTIBILITY AREA
20
CURRENT (dBmA)
CURRENT (dBmA)
50
50
46
40
Susceptibility Points
NO SUSCEPTIBILITY AREA
30
20
10
10
1.0
10
100
1000
1.0
FREQUENCY (MHz)
MC33388
MOTOROLA
10
100
1000
FREQUENCY (MHz)
13
MC33388
OUTLINE DIMENSIONS
Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty, representation or guarantee regarding the suitability
of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all
liability, including without limitation consequential or incidental damages. “Typical” parameters which may be provided in Motorola data sheets and/or specifications can and do
vary in different applications and actual performance may vary over time. All operating parameters, including “Typical” must be validated for each customer application by
customer’s technical experts. Motorola does not convey any license under its patent rights nor the rights of others. Motorola products are not designed, intended, or authorized for
use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any application in which the failure of the
Motorola product could create a situation where personal injury or death may occur. Should Buyer purchase or use Motorola products for any such unintended or unauthorized
application, Buyer shall indemnify and hold Motorola and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and
expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or un authorized use, even if
such claim alleges that Motorola was negligent regarding the design or manufacture of the parts. Motorola and
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2, Dai King Street, Tai Po Industrial Estate, Tai Po, N.T., Hong Kong.
852-26668334
Order this document by SPTC Marketing
Rev: 2.2 Date: 02 Nov 2000
MC33388
Advance Information
Fault Tolerant CAN Interface
The MC33388 is a CAN physical interface device, dedicated to
automotive body electronic multiplexing applications. It operates in
differential mode, allowing ground shifts up to 1,5V, reducing RFI
disturbances. It offers very low standby current in sleep and standby
mode operation and supports communication speeds up to 125kBauds.
It is fully protected against harsh automotive environments and the
driver is able to detect fault conditions and automatically switches into
appropriate default mode. Under fault condition, it continuously monitors
bus failures in order to switch back to normal bus operation as soon as
faults disappeared.
AUTOMOTIVE FAULT TOLERANT
CAN PHYSICAL LAYER
SEMICONDUCTOR
TECHNICAL DATA
• Very low sleep/standby current (15µA typical)
• Baud rate from 10 kBaud up to 125kBauds
• Automatic switching to single wire mode in case of bus failures and
return to differential mode if bus failures disappear
• Supports one wire transmission modes with ground offset up to 1.5V
• Internal bus driver slope control function to minimize RFI
• Bus line short-circuit protected to battery, VDD and ground
• Bus line protected against automotive transients
• Thermal protection of bus line drivers
• Supports unshielded twisted pair bus
• An unpowered node does not disturb the bus lines
• Wake-up capability triggered from bus message and wake-up input pin
• Wake up pin with dual edges sensitivity
• Battery fail flag reported on NERR output
• Ambient temperature range from -40°C to 125°C.
D SUFFIX
PLASTIC PACKAGE
CASE 751A-03
SO-14
PIN CONNECTIONS
Simplified Block Diagram
VDD
WAKE
EN
STB
INH
WAKE-UP LOGIC
MODE CONTROL
1
14
BAT
TX
2
13
GND
RX
3
12
CANL
NERR
4
11
CANH
STB
5
10
VDD
EN
6
9
RTL
WAKE
7
8
RTH
12.5k
VDD
PROTECTION
S5
S2
S3
(Top View)
RTL
SLOPE
CONTROL
&
DRIVER
TX
INH
BAT
CANH
CANL
RTH
S4
S1
NERR
FAILURE DETECTION
RECEIVER
RX
ORDERING INFORMATION
MUX
GND
Device
Operating
Temperature Range
MC33388D
TA = -40 to 125°C
Package
SO-14
MC33388
MAXIMUM RATING
Ratings
Symbol
Min
DC Supply Voltage Pin 10
VDD
DC Voltage On Pins 2, 3, 4, 5, 6 and 7
DC Voltage On Pins 11, 12
Transient Voltage At Pins 11, 12
0 < VDD < 5.5V ; V BAT≥ 0 ; T < 500ms
Transient Voltage On Pins 11, 12 (Coupled Through 1nF
Capacitor)
Typ
Max
Unit
-0.3
6
V
VDD
-0.3
VDD + 0.3
V
VBUS
-20
+27
V
VCANH/VCANL
-40
40
V
Vtr
-150
100
V
VBAT +0.3
V
DC Voltage On Pin 7
Vwake
Current In Pin 7
I wake
-15
3
mA
Vinh
-0.3
VBAT + 0.3
V
DC Voltage On Pins 8, 9
Vrtl, Vrth
-0.3
40
V
DC Voltage On Pins 14
VBAT
-0.3
27
V
Voltage On Pins 14 (Load Dump, 500ms)
VBAT
40
V
ESD Voltage On Any Pins (HBM.100pF ; 1.5kΩ)
VESD
-3.0
3.0
kV
ESD Voltage On Any Pins (MM.200pF ; 0Ω)
VESD
-200
200
V
Junction Temperature
Tj
-40
150
°C
Storage Temperature
Tstg
-55
150
°C
Rt
500
16000
Ω
Symbol
Value
Unit
Rth j/a
120
°C/W
Typ
Max
Unit
DC Voltage On Pins 1
RTH, RTL Termination Resistance
THERMAL RATINGS
Ratings
Thermal Resistance From Junction To Ambient
ELECTRICAL CHARACTERISTICS VDD = 4,75 to 5,25 ; VBAT=6 to 27V ; Tamb = -40 to 125°C unless otherwise specified
Conditions
Symbol
Min
SUPPLY
Vdd Supply Current (Normal Mode)
TX= VDD, Recessive State
IVDD
2.3
3
mA
Vdd Supply Current (Normal Mode)
TX = 0V, No Load, Dominant State
IVDD
3.3
5
mA
Vbat Supply Current (Normal Mode)
TX = VDD
IBAT
150
300
µA
Total Supply Current (Receive Only Mode)
VDD = 5V ; V BAT = 12V
IVDD + IBAT
0.85
1.2
mA
Total Supply Current (Vbat Standby Mode)
VDD = 5V ; V BAT = 12V
IVDD + IBAT
20
40
µA
IBAT
15
25
µA
Vbat Supply Current (Sleep Mode)
VDD = 0V ; V BAT = 12V
MC33388
MOTOROLA
2
MC33388
ELECTRICAL CHARACTERISTICS VDD = 4,75 to 5,25 ; VBAT=6 to 27V ; Tamb = -40 to 125°C unless otherwise specified
Conditions
Symbol
Min
Typ
Max
Unit
High Level Input Voltage
Vih
0.7*VDD
VDD+0.3V
V
Low Level Input Voltage
Vil
-0.3
0.3 * V DD
V
High Level Input Current (STB, EN) (V i = 4V)
Iih
40
µA
Low Level Input Current (STB, EN) (Vi = 1V)
Iil
10
20
TX High Level Input Current (Vi = 4V)
ITX
-25
-80
-200
µA
TX Low Level Input Current (Vi = 1V)
ITX
-100
-320
-800
µA
Forced V BAT Standby Mode (Fail Safe) Threshold
VDD
3
4
4.7
V
Battery Voltage For Setting Power On Flag
VBAT
1.5
3
4
V
High Level Output Voltage NERR (I0 = -100µA)
Voh
VDD - 0.9
VDD
V
High Level Output Voltage RX (I0 = -250µA)
Voh
VDD - 0.9
VDD
V
Low Level Output Voltage (I 0 = 1.5mA)
Vol
0
0.9
V
STB, EN, TX Pins
20
µA
RX, NERR Pins
WAKE Pin (must be connected to gnd or BAT if not used)
Typical Wake Up Threshold (VSTB = 0V), High to Low
Transition, VBAT=6V to 18V. NOTE1.
Wuthreshl
0.44 V BAT
V
Typical Wake Up Threshold (VSTB = 0V), Low To High
Transition, VBAT=6V to 18V. NOTE1.
Wuthreslh
0.57 V BAT
V
Wake Up Threshold Hysteresis
Wuhyst
500
mV
Wake Up Threshold, High to Low Transition at V BAT=12V
Wuhl
3.6
6.5
V
Wake Up Threshold, Low To High Transition at VBAT=12V
Wulh
6.2
7.5
V
High Level Voltage Drop (IINH = -0.2mA, INH High)
Vdrop
0
0.8
V
Leakage Current (Sleep Mode ; V INH = 0V)
Il inh
0
5
µA
Differential Receiver, Recessive To Dominant Threshold
(By Definition, V diff=VCANH-VCANL)
Vdiff1
-3.2
-2.5
V
Differential Receiver, Dominant To Recessive Threshold
(Bus Failures 1, 2, 5)
Vdiff2
-3.2
-2.5
V
0.2
V
INH Pin
CANH, CANL Pins
CANH Recessive Output Voltage
TX = VDD ; R (RTH) < 4k
VCANH
CANL Recessive Output Voltage
TX = VDD ; R (RTL) < 4k
VCANL
VDD - 0.2
V
CANH Output Voltage, Dominant
TX = 0V; I CANH = -40mA; Normal Operating Mode
VCANH
VDD - 1.4
V
MC33388
MOTOROLA
3
MC33388
ELECTRICAL CHARACTERISTICS VDD = 4,75 to 5,25 ; VBAT=6 to 27V ; Tamb = -40 to 125°C unless otherwise specified
Conditions
Symbol
Min
Typ
Max
Unit
1.4
V
CANL Output Voltage, Dominant
TX = 0V; I CANL = 40mA; Normal Operating Mode
VCANL
CANH Output Current (VCANH = 0 ; TX = 0)
ICANH
50
75
100
mA
CANL Output Current (VCANL = 14V; TX = 0)
ICANL
50
90
130
mA
Detection Threshold For Short-circuit To Battery Voltage
(Normal Mode)
VCANH, V CANL
7.3
7.9
8.9
V
Detection Threshold For Short-circuit To Battery Voltage
(Standby/Sleep Mode)
VCANH
VBAT/2 +3
VBAT /2+5
V
5
10
µA
0
2
µA
CANH Output Current (Sleep Mode; V CANH = 12V, Failure3)
CANL Output Current (Sleep Mode ; V CANL = 0V ;
VBAT = 12V, Failure 4)
ICANL
CANL Wake Up Voltage Threshold
Vwake,L
2.5
3.3
3.9
V
CANH Wake Up Voltage Threshold
Vwake,H
1.2
2
2.7
V
VwakeL-VwakeH
0.2
CANH Single Ended Receiver Threshold (Failures 4, 6, 7)
VSE, CANH
1.5
1.85
2.15
V
CANL Single Ended Receiver Threshold (Failures 3, 8)
VSE, CANL
2.8
3.05
3.4
V
CANL Pull Up Current (Normal Mode, Failures 4, 6 and 7)
ICANL,pu
45
75
90
µA
CANH Pull Down Current (Normal Mode, Failure 3)
ICANH,pd
45
75
90
µA
Receiver Differential Input Impedance CANH / CANL
Rdiff
100
180
kΩ
Differential Receiver Common Mode Voltage Range
Vcom
-10
10
V
Wake Up Threshold Difference (Hysteresis)
V
CANH To Ground Capacitance
CCANH
50
pF
CANL To Ground Capacitance
CCANL
50
pF
CCANL to C CANH Capacitor Difference (Absolute Value)
DCcan
10
pF
RTH, RTL Pins
RTL to VDD Switch On Resistance (I out < -10mA; Normal
Operating Mode)
Rrtl
10
30
50
Ω
RTL to BAT Switch Series Resistance (VBAT Standby Mode
Or Sleep Mode)
Rrtl
8
12.5
20
kΩ
RTH To Ground Switch On Resistance (I out <10mA; Normal
Operating Mode)
Rrth
10
25
50
Ω
Thermal Shutdown
Shutdown Temperature
MC33388
Tsd
MOTOROLA
165
°C
4
MC33388
AC CHARACTERISTICS VDD = 4,75 to 5,25 ; VBAT=6 to 27V ; Tamb = -40 to 125°C unless otherwise specified
CANL and CANH Slew Rates (10% to 90%).
Rising or Falling Edges. NOTE2.
Tsl
3.5
5
10
V/µs
Propagation Delay TX to RX Low. NOTE2.
Tpdlow
1
2
µs
Propagation Delay TX to RX High. NOTE2.
Tpdhigh
1
2
µs
Min. Dominant Time For Wake-up On CANL or CANH
(Vbat Standby And Sleep Modes ; V BAT = 12V)
Twake
8
16
30
µs
Min. WAKE Time For Wake-up
(Vbat Standby And Sleep Modes ; V BAT= 12V)
Twake
6
15
30
µs
Failure 3 Detection Time (Normal Mode)
Tdf3
10
60
µs
Failure 6 Detection Time (Normal Mode)
Tdf6
50
400
µs
Failure 3 Recovery Time (Normal Mode)
Tdr3
10
60
µs
Failure 6 Recovery Time (Normal Mode)
Tdr6
150
1000
µs
Failure 4, 7, 8 Detection Time (Normal Mode)
Tdf478
0.75
4
ms
Failure 4, 7, 8 Recovery Time (Normal Mode)
Tdr478
10
60
µs
Failure 3, 4, 7,8 Detection Time
(Vbat Standby And Sleep Modes ; V BAT = 12V)
Tdr347
0.8
8
ms
Failure 3, 4, 7,8 Recovery Time
(Vbat Standby And Sleep Modes ; V BAT = 12V)
Tdr347
2.5
ms
38
µs
0.75
4
ms
10
60
µs
Minimum Hold Time For “Go To Sleep” Command
Tgts
4
Edge Count Difference Between CANH and CANL for
Failures 1, 2, 5 Detection (NERR Becomes Low), (Normal Mode)
Ecdf
3
Edge Count Difference Between CANH And CANL For
Failures 1, 2, 5 Recovery (Normal Mode)
Ecdr
3
TX Permanent Dominant Timer Disable Time
(Normal Mode And Failure Mode)
tTX,d
TX Permanent Dominant Timer Enable Time
(Normal Mode And Failure Mode)
tTX,e
NOTE:
1. When VBAT is greater than 18V, the wake up thresholds remain identical to the wake up thresholds at 18V.
2. AC Characteristics measured according to schematic figure 2.
MC33388
MOTOROLA
5
MC33388
Figure 1. Device Signal Waveforms
Tx high: RECESSIVE Bit
Tx high: RECESSIVE Bit
VTX
Tx low: DOMINANT Bit
5V
CANL
3.6V
1.4V
0V
CANH
2.2V
Vth(dr)
0.7V
Vdiff
-2.9V
Vth(rd)
toffTX
-5V
VRX
0.7VCC
0.3VCC
tonRX
toffRX
t
RECESSIVE Bit
DOMINANT Bit
RECESSIVE Bit
Figure 2. Test Circuit For AC Characteristics
VDD
R
C
CANL
C
CANH
R
C
R = 100ohms
C = 1nF
MC33388
MOTOROLA
6
MC33388
DEVICE DESCRIPTION
Introduction
The MC33388 is a low speed CAN fault tolerant physical
interface designed for automotive multiplexed electronic
systems. The MC33388 addresses the low speed body
electronics application, in which the speed of communications
is between 10 and 125kBauds, on two wires bus
configurations. It is designed to operate in the harsh
automotive environment.
The MC33388 can control the external voltage regulator of
the system through the dedicated INH pin. It allows the
application to be switched into low power mode. Wake up can
be done either from bus activity or local wake up switch. The
MC33388 is tolerant to faults occurring at the CAN bus in
normal operating mode and low power mode.
Packaging
The device is assembled in a SO14 narrow body package.
Thermal performances allow the device to operate in the
automotive ambient temperature range, from –40°C to 125°C.
Transmitter Function
CAN bus levels are called Dominant and Recessive, and
correspond respectively to Low and High state of TX input pin.
The Recessive state is a weak state, where bus line are driven
through pull up and pull down resistors. Recessive state can
be over written by any other node forcing a Dominant state, in
which bus line are driven through active switches.
The bus is terminated by pull up and pull down resistors,
which are connected to GND, VDD or VBAT through
dedicated Rtl and Rth pins and internal circuitry.
The bus line slew rates are controlled in order to minimize
the RFI and this allows use of unshielded cables for the bus.
Receiver Function
In normal operation (no bus failures), RX is the image of
the differential bus voltage. The differential receiver inputs are
connected to CANH and CANL through integrated filters. The
filtered input signals are also used for the single wire
receivers.
The device incorporates comparators connected to CANH
and CANL in order to monitor and report the bus state to the
microcontroller as well as detect bus failures. Failures are
reported back to the microcontroller through NERR pin.
In normal operation when no failure is present the
differential comparator is active. Under fault condition, one of
the two CANH or CANL pin can be non operational then the
single ended comparator of either CANH or CANL is activated
and continue to report bus state to the microcontroller. The
MC33388 permanently monitors bus failure and recovery,
and as soon as fault disappears, it automatically switches
back to differential operation.
Noise Filtering
The device is optimized for dual wires operations. During
all single wire transmissions, the EMC performances in both
immunity and emission are worse than in differential mode.
Integrated receiver filters suppress any HF noise induced into
the bus wires. The cut-off frequency of these filters is a
compromise between propagation delay and HF suppression.
In single wire mode, low frequency noise can not be
distinguished from the active signal at the bus line.
MC33388
Device Operation Mode
The device has four operation modes : Normal, Receive
Only, Standby VBAT and Sleep. Each of these modes is
controlled by the state of EN and STB pins.
The state machine figure 3 and the truth table 1 indicate
how to configure the device into each mode and the pins
functions in each operation mode.
Operation Mode
Normal mode: In this mode, all functions are available and
NERR pin reports bus failure
Receive Only mode: In this mode, the transmitter path is
disabled, so the device do not drive the bus. It maintains
CANL and CANH in recessive state. The receiver function
operates normally. As the device can not drive the bus, an
incoming CAN message could not be acknowledge by the
node. NERR output signals the VBAT power-on flag and RX
reports bus state. Failure detection and management are the
same as in normal mode.
Sleep mode: In this mode, the transmitter and receiver
functions are disabled. CANL pin is connected to VBAT
through Rtl resistor and internal pull up resistor of 12.5kOhms.
INH pin is switched in high impedance state. The external
voltage regulator connected to INH will be switched off and no
VDD is supplied to MC33388. In this mode the device is still
supplied by the VBAT. Supply current from VBAT is 15uA
typical. The MC33388 monitors the bus activity and the state
of WAKE pin and VBAT level. If wake up conditions are
encountered, the device wakes up to Standby VBAT mode
and INH is switched on.
Standby VBAT mode: This mode is similar to Sleep mode,
but the INH pin is in high state in order to maintain the external
5V regulator activated. Wake up events are directly reported
to NERR and RX thanks to the 5V available at VDD. CANL is
in the same configuration as in Sleep mode.
Standby and Sleep modes are active when STB and EN
are low. Selection of Standby or Sleep is done through the
sequence of activation of EN and STB pins. Sleep mode is
entered through an intermediate steps (go to sleep) where
STB, EN are 0, 1. (Refer to truth table 1).
System Power On
When the supply is first applied to the system, VBAT and
VDD rise from zero up to their nominal value and the device
automatically enters into VBAT standby mode. At this time,
INH is switched in high state in order to activate the external
voltage regulator and an internal flag is set (batt fail flag). EN
and STB pins are internally forced in low state to maintain the
device into VBAT standby mode.
The VDD “forced Vbat standby mode (fail safe)” circuit will
maintain the device in VBAT standby mode until VDD is
higher that 3V, whatever the external state of EN and STB.
As soon as VDD reaches the “forced VBAT standby mode
(fail safe)” threshold, the device can enter into other mode,
depending upon EN and STB state.
VDD Reset Function
If during operation VDD drops below “forced VBAT standby
mode (fail safe)” threshold, the device is automatically switched
into VBAT standby mode to provide fail safe functionality.
MOTOROLA
7
MC33388
DEVICE DESCRIPTION
Battery Fail Flag
When the VBAT supply drops below “battery voltage for
setting power on flag” threshold, this information is internally
latched. This means that the system power supply has been
lost (disconnected and reconnected for instance).
This flag can be read by the microcontroller by switching
the device into receive only mode, where NERR pin reports
the VBAT power on flag. This flag is reset by entering into the
Normal mode.
Bus Failure Detection
The device permanently monitors the bus lines and
detects faults in normal and receive only modes. Below is the
list of failures detected at the bus level :
1- CANH wire interruption
2- CANL wire interruption
3- CANH short-circuit to battery
4- CANL short-circuit to ground
5- CANH short-circuit to ground
6- CANL short-circuit to battery
7- CANL and CAN H mutually shorted
8- CANH short-circuit to Vdd
TX Permanent Dominant Detection
In addition to the above list, the MC33388 detects a
permanent low state at TX input which results of a permanent
dominant bus state. The MC33388 detects if TX is Low for
more than 2ms typical and then disables the bus output driver
in order to switch into recessive state. This avoid to block
communication between other nodes of the network.
Behaviour Under Faults Condition
When a fault is detected, the device automatically takes
appropriate action to minimize the system current
consumption and to allow communication on the network.
Depending on the type of fault, the mode of operation and the
fault detected, the device automatically switches off one or
more of the following functions: CANL or CANH line driver, Rtl
or Rth pull up or down resistors or internal switches. These
actions are detailed in table 2.
The device permanently monitors the faults and in case of
fault recovery, it automatically switches back to normal
operation and reconnects the open functions. Faults detection
and recovery circuitry have internal filters and delays timing
detailed in the AC characteristics parameters section.
Detailed Description of Error Detections
The differential receiver threshold is set at -2,8V. This
assures a proper reception in the normal operating modes
and in case of failures 1, 2 and 5 noise margin as high as
possible. These failures or their recovery do not destroy
ongoing transmissions.
MC33388
Failures 3 and 6 are detected by comparators respectively
connected to CANH and CANL. If the comparator threshold is
exceeded for a certain time, the device is switched to single
wire mode. This time is needed to avoid false triggering by
external RF fields. Recovery from these failures is detected
automatically after a certain time-out (filtering) and no
transmission is lost.
Failures 4, 7 and 8 initially result in a permanent dominant
level at the internal comparator outputs. If failure 4 and 7
appear, the CANL driver and the RTL pin are switched off
after a time out, only a weak pull up at RTL remains.
Reception continues by switching to single wire mode through
CANH. When the failures 4 or 7 are removed, the recessive
bus levels are restored. If the receiver voltages remain in the
recessive state for a certain time, reception and transmission
switch back to the differential mode.
If failure 8 is recognized, the CANH driver is switched off
after a time out and the reception is switched to single wire
mode through CANL. If the receiver voltages remain in the
recessive state for a certain time, reception and transmission
switch back automatically to the differential mode.
If any of the 8 wiring failure occurs, the output NERR will
be switched low. When the error recovers, NERR will be
switched back to high state.
Wake Up Events
Wake-up requests are recognized by the MC33388 in
Sleep or VBAT Stanby modes, either when a dominant state
is detected on CANL or CANH bus lines (remote wake-up) or
if the WAKE pin changes state (local wake-up).
Under power-up conditions when VBAT is higher than 5V,
the state voltage on the WAKE pin is considered to be the
reference state for the wake-up function. On leaving normal
mode, the current WAKE pin state becomes the new
reference state.
In sleep mode, on a wake-up request the transceiver sets
the INH output high, to activate the external voltage regulator,
used for VDD supplied. In VBAT standby INH is already set
high. When VDD is set, the wake-up request can be read on
the NERR or RX outputs by the microcontroller.
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 low power modes, failure detection circuit remains
partly active to prevent increased power consumption in
cases of error 3, 4, 7 and 8.
Fault Operation Table
Table 2 shows the device operation in normal and low
power modes and the internal actions happening under fault
condition. Please refer to simplified block diagram page 1 for
device internal switch reference.
MOTOROLA
8
MC33388
DEVICE DESCRIPTION
Figure 3. State Machine And Operation Modes
Normal mode (1, 1)
(0, 1)
Go to sleep mode (0, 1)
(BUS failure, ON)
(1, 1)
(Wake up event, OFF3)
(0, 0)
(1, 1)
(1, 1)
(1, 1)1
(1, 0)
Sleep mode (0, 0)
(0, 0)
(1, 0)
(1, 0)1
(0, 0)4
(Wake up event1,2, OFF)
(0, 1)
(0, 1)
wake-up event
(bus message, wake pin)
Receive Only mode (1, 0)
(0, 0)
Stand-by VBAT mode (0, 0)
(VBAT fail flag, ON)
(1, 0)
(Wake up event, ON)
power up
Legend:
Transceiver mode (STB state, EN state)
(NERR function, INH state)
NERR: BUS - Bus error is flagged
WAKE - Wake-up event is flagged
BAT - BAT fail is flagged
1
with permanent VDD
2
VDD is still switched on
3
if no wake-up occurs after 25µs
4
as long as INH is on
INH: ON - INH is switched on
OFF - INH is floating
Table 1 • Truth Table
STB
EN
Mode
INH
0
0
VBAT
Standby1
High
0
0
Sleep2
Floating
0
1
Go to sleep
command
Floating
1
0
Receive Only3
High
1
1
Normal
High
NERR
RX
Active LOW:
wake-up interrupt signal
(if V DD is present)
RTL
IDD (4)
IBAT (4)
Switched to
VBAT
5µA
typ. 15µA
Switched to
VBAT
Not
applicable
typ. 15µA
Switched to
VBAT
Active LOW:
VBAT power-on flag
High: recessive state
Low: dominant state
Active LOW:
error flag
Switched to
VDD
800µA
Switched to
VDD
2.3mA (5)
3.3mA (6)
typ.
150µA
NOTES:
1. Wake-up interrupts are released when entering normal operating mode.
2. If go to sleep command was used before (EN may turn LOW as VDD drops, without affecting internal functions because of fail safe functionality.
3. VBAT power-on flag will be reset when entering normal operation mode.
4. Value are typical, without bus load current.
5. In recessive state.
6. In Dominant State, value with no load at bus.
MC33388
MOTOROLA
9
MC33388
DEVICE DESCRIPTION
Table 2 • Detail Fault Operation Table
Mode
State of S1, S2, S3 Internal Switches and CANL CANH Output
Drivers (Ref to Normal Mode)
No failure
Normal and
receive only
S1, S2 closed, CANL, CANH drivers enabled
No failure
VBAT standby
S3 closed, CANL, CANH drivers disabled
No failure
Sleep mode
S3 closed, CANL, CANH drivers disabled
Failure #
Description
1
CANH wire interrupted
Normal and
receive only
CANL, CANH drivers enabled, S1, S2 closed
2
CANL wire interrupted
Normal and
receive only
CANL, CANH drivers enabled
S1, S2 closed
3
CANH short to BAT
All
S1 open, CANH driver disabled
4
CANL short to GND
All
S2, S3 open & CANL driver disabled
5
CANH short to GND
Normal and
receive only
CANL, CANH drivers enabled
S1, S2 closed
6
CANL short to BAT
Normal and
receive only
S2, S3 open & CANL driver disabled
7
CANL short to CANH
All
S2, S3 open & CANL driver disabled
8
CANH short to VDD
All
S1 open, CANH driver disabled
NOTE: S4 and S5 behaviours are only dependant upon the device operating mode.
S4 and S5 switches are closed in normal and receive only modes and are open in sleep and standby modes.
MC33388
MOTOROLA
10
MC33388
PIN FUNCTION DESCRIPTION
VBAT (input) : This is the supply line of the device. It can
be directly connected to the battery line, can operate up to
27VDC and sustains up to 40V during load dump condition.
The supply current is dependant upon the device operation
mode. In low power mode, it is as low as 12uA typical. A
battery fail flag circuitry is associated to this pin.
The Vbat pin must be protected by external component
against reverse battery and negative transient voltages.
VDD (input) : 5V input supply voltage for the device. In
normal mode, the current is up to 5mA typical and do not
exceed few uA in Vbat standby mode. An under voltage
function is associated to Vdd and resets the device to Vbat
standby mode when Vdd falls below 3V.
CANH : Bus output driver pin. CANH is a high side switch
structure connected to VDD supply. In recessive state, the
high side switch is off and bus CANH line is biassed through
the Rth pin circuitry and external Rth resistor. In dominant
state, high side switch is on and CANH line is switched to
VDD. Output voltage is above 3.6V. CANH output is protected
against short-circuit to ground, by internal current limitation. A
thermal shutdown with hysteresis switches off CANH driver if
temperature rises above 150°C. CANH is also protected
against short-circuit to higher voltage, such as VBAT by an
internal serial diode in series with the switching component.
CANH has a pull down current source, typically 75uA, which
can be activated under some fault condition.
Rth : Connection to the CANH bus terminal resistors. Rth
output structure is a low side switch, turned on under normal
condition and automatically desactivated under some fault
condition. In the application, an external resistor is connected between Rth and CANH pins. In recessive state
when CANH driver is off, CANH line is tied to ground through
the external Rth resistor.
CANL : Bus output driver pin. CANL is a low side switch
structure to the ground. In recessive state, the low side switch
is off, and bus CANL line is biassed through the Rtl circuitry
and external Rtl resistor. In dominant state, low side switch is
on and CANL line is switched to ground. Output voltage is
below 1.4V. CANL output is protected against short-circuit to
VBAT, by internal current limitation. A thermal shutdown with
hysteresis is integrated and switches off CANL driver if
temperature rises above 150°C. CANL is protected against
negative voltage, by an internal serial diode in series with the
switching component. CANL has a pull up current source,
typically 75uA, activated under some fault condition.
Rtl : Connection to the CANL bus terminal resistors. Rtl
output structure is a low side switch, turned on under normal
condition and automatically desactivated under some fault
condition. In the application, an external resistor is connected
between Rtl and CANL pins. In recessive state when CANL
driver is off, CANL line is tied to VDD through external Rtl
resistor.
In VBAT Standby and Sleep modes, Rtl pin is connected
to the VBAT line through an internal switch and a 12.5kΩ
resistor. This means that in these modes CANL bus line is
biassed to VBAT. Wake up from these modes are detected by
CANL line going from VBAT level to CANL wake up threshold
level.
MC33388
STB and EN : Input pins used to configure the device into
desired mode. These pins are CMOS compatible and are
connected to the microcontroller of the application.
INH : This is an output of the MC33388 used to control an
external voltage regulator having an inhibit input. INH is a high
side switch structure, active when the MC33388 is in normal,
Receive only or Standby VBAT modes. INH is switched off in
Sleep mode to switch off the voltage regulator of the
application. INH has no pull down structure.
WAKE : This is a high voltage input used to wake up the
device from Sleep and VBAT Standby modes. Wake is
usually connected to an external switch in the application. The
typical wake thresholds are Vbat/2.
Wake pin has special design structure and allows wake up
from both high to low or low to high transitions. When entering
into the Sleep or VBAT Standby mode, the MC33388
monitors the state of the wake pin and stores it as reference
state. The opposite state of this reference state will be the
wake up event used by the device to enter again into normal
mode.
An internal filter is implemented, with 8 to 38 µs filtering
time delay. Wake pin input structure exhibits a high
impedance, with extremely low input current. A serial resistor
should be inserted in order to limit the input current mainly
during transient pulses.
CAUTION : The Wake pin should not be left open. If wake
up function is not used, wake should be connected to GND to
avoid false wake up.
TX : Transmitter input pin to control bus state. It is CMOS
compatible and usually directly connected to the TX output of
a microcontroller. When TX is at high state, CANH and CANL
are in recessive state. When TX is low, CANL and CANH are
in dominant state. Special fault handling is provided to this
input, in order to detect permanent dominant state (TX low)
which would result of CAN bus permanently lock in dominant
state and do not allow communication. In case where TX is
low for more than 2ms typical, the device automatically
switches the bus lines to recessive. TX has an internal pull up
resistor to VDD.
RX : Output receiver connection to the microcontroller. It
reports the bus state to the RX input pin of the microcontroller.
RX is high when bus is recessive and low in dominant state. In
sleep and standby Vbat modes, RX reports wake up events.
NERR : Error output pin which reports errors encountered
by the device. When NERR is high, no error is reported, when
NERR is low an error has been detected. In Standby VBAT
mode NERR reports a wake up event. In receive only mode,
NERR reports VBAT power on flag.
Table 3 • Truth Table of RX, TX CAN Bus States
TX
RX
Bus States
Low
Low
Dominant
High
High
Recessive
High
Low
Dominant
MOTOROLA
Comment
Bus Driven By Other Node
11
MC33388
APPLICATION
Table 4 • Typical Application Schematic
BATTERY
BATTERY
IC1
5V
Switch
D1
R4
C2
12V
R4
Switch
C3
C4
WAKE
INH
VDD
RTH
C1
Vdd
option with switch to gnd
R3
VBAT
R1
L1
CANH
EN
MCU
CAN BUS
I/O
Port
STB
CANL
NERR
R2
TX
CAN
RTL
MODULE
RX
GND
MC33388D
Vss
R3
Figure 4 above is the typical application schematic. All
MC33388 capabilities are utilized : CAN interface, normal
and low power modes, wake up source from CAN bus or
wake up switch.
The MC33388 VDD is supplied through an external
voltage regulator having an inhibit input pin. In addition to TX
and RX connections to the microcontroller CAN module, the
MC33388 requires 3 additional connections to a standard
microcontroller I/O port for EN, STB and NERR pins.
MC33388 wake pin is connected to an external signal
switch. MC33388 allows the signal switch configuration to be
either connected to Vbat or to ground through pull up or pull
down resistor. Solution with switch to GND is indicated as
option in the application schematic. A resistor must be
inserted in series with wake pin in order to limit the input
current during positive and negative transient pulses.
De-coupling capacitors are recommended on the
MC33388 VBAT and VDD lines. Those capacitors might be
shared with other devices from the same printed circuit
board, depending on its configuration.
R1 and R2 are the network termination resistors. For
proper operation, they must have identical value (R1 equals
Component information:
R3: 10kΩ
R4: >= 33kΩ
C1>= 47nF
C2>= 4.7uF
C3>= 47nF
C4>= 10uF
L1: optional common mode choke
D1: 1N4148
IC1: LM2935
R1=R2=R (500Ω<R<16kΩ)
R/number of nodes>100Ω
to R2). Their value is determined by the total network
termination resistor and the number of nodes.
The total network termination resistor value must be
higher than 100Ω. If a 500Ω termination resistor is chosen,
with a system composed of 32 nodes, each R1 or R2 will be
16kΩ. In addition, R1 and R2 values should be chosen
between 500Ω and 16kΩ at each node.
The CANH and CANL pin can be directly connected to the
CAN bus. A serial common mode inductance can be inserted
in order to improve electromagnetic compatibility
performances both in emission and susceptibility.
Minimum Application Configuration
The minimum device configuration is described in
minimum application schematic figure 5 below. The device is
used as CAN transceiver only and other features are not used.
The device EN and STB input pins must be connected to 5V in
order to set the device in normal mode. INH and NERR can be
left open.
CAUTION : WAKE should not be left open and must be
connected to a known state, i.e GND.
Figure 4. Minimum Application Schematic
BATTERY
D1
C3
C4
5V
C2
INH
VBAT
RTH
VDD
Vdd
C1
EN
R1
STB
MCU
WAKE
CANH
CAN BUS
NERR
Component information:
C1>= 47nF
C2>= 4.7uF
C3>= 47nF
C4>= 10uF
D1: 1N4148
R1=R2=R (500Ω<R<16kΩ)
R / number of nodes>100Ω
CANL
R2
CAN
MODULE
Vss
MC33388
TX
RTL
RX
MC33388D
GND
MOTOROLA
12
MC33388
Electromagnetic Compatibility
Introduction
The device is designed for optimized noise emission (EMI)
and high susceptibility performances (EMC). The source for
both disturbance and susceptibility is primarily coming form the
bus line wires. They are by far the longest connections
compared to the printed circuit board of the application
receiving the MC333388, the microcontroller and the other
components.
CAUTION : The common mode voltage characteristics are
dependant upon immediate device environment, such as bus
capacitor loading, bus wire length and type, etc... In addition, the
symmetry of the CANL and CANH bus lines is key parameter to
optimize common mode glitches. For instance un-symmetry
could result in different parasitic capacitors value between
CANL to GND and CANH to GND and will increase common
mode glitches and degrade overall system performances.
EMI Noise
In order to minimize the HF noise generated by the
complete application, the MC33388 minimizes the common
mode voltage and current glitches occurring at each bus
transition : from dominant to recessive and from recessive to
dominant. This is achieves by excellent matching in signal
transition between CANL and CANH. The common mode
voltage and current glitches are defined as follow :
CmV = (Vcanh+Vcanl)/2,
CmI = (Icanh+Icanl)/2.
The device is optimized for dual wires operations. Under a
fault condition, for instance one CAN bus connection shorted to
fixed voltage, e.g GND, the common mode will be considerably
degraded.
Figure below shows the typical signals for common mode
voltage measured at CANL and CANH pins.
EMC Susceptibility Performances
The MC33388 is optimized for high immunity from external
field disturbances. The bus lines are by far the primary antenna
for external field coupling to the CANL, CANH, Rtl and Rth
connections. The device performances are characterized using
the Bulk Current Injection (BCI) test method, derivated from
specification ISO 11452-4.
Susceptibility evaluation with BCI :
The component is configured according to the electrical
schematic very close to the typical application schematic, figure
4. Main difference is that the microcontroller is replaced by an
external generator and analyzer connected to RX, TX and
NERR through optical link. A network composed of two nodes
equipped with MC33388, one in emitter and one in receiver is
evaluated. The disturbance is applied to both CANL and CANH
twisted pair bus line lines with appropriate coupling clamp.
During test sequences, received bits are compared to
transmit bits. When received bits are different from transmit bits
the device is considered as fail for the particular frequency.
Figure 5. Typical Common Mode Glitch
Measured at CANL CANH
Results
Figures 7 and 8 below describe the device susceptibility
performances in the frequency range of 1 to 400MHz with target
of injected current of 200mA and 316mA.
When the target current is reached and when no
susceptibility is observed, the next frequency point is analyzed,
until reaching the max frequency, 400Mhz. If a susceptibility is
observed for a particular frequency, the free point is marked.
Figure 7 below shows results with a target susceptibility level
of 316mA or 49dBmA with a 1KHz 80% modulation added to the
injected current. Figure 8 shows the susceptibility levels with a
target susceptibility level of 200mA or 46dBmA without
modulation added to the injected current.
NERR: 5V/div
Common Mode
Glitch
100mV/div
Tx: 5V/div
Figure 7. Min. Susceptibility Level Without Modulation
Figure 6. Min. Susceptibility Level With Modulation
60
60
LIMIT OF TEST (46dB) (No Susceptibility)
LIMIT OF TEST (49dB) (No Susceptibility)
40
Susceptibility Points
30
NO SUSCEPTIBILITY AREA
20
CURRENT (dBmA)
CURRENT (dBmA)
50
50
46
40
Susceptibility Points
NO SUSCEPTIBILITY AREA
30
20
10
10
1.0
10
100
1000
1.0
FREQUENCY (MHz)
MC33388
MOTOROLA
10
100
1000
FREQUENCY (MHz)
13
MC33388
OUTLINE DIMENSIONS
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