MC33388 Datasheet, PDF (12/28 Pages) Motorola, Inc – Fault Tolerant CAN Interface

C2
Vdd
C1
MCU
I/O
Port
CAN
MODULE
Vss
MC33388
APPLICATION
Table 4 • Typical Application Schematic
BATTERY
IC1
5V
D1
12V
Switch
R4
C4
C3
VBAT
INH
VDD
WAKE
RTH
EN
STB
NERR
CANH
CANL
TX
RX
MC33388D
RTL
GND
R3
R1
L1
CAN BUS
R2
BATTERY
R4
R3
Switch
option with switch to gnd
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
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
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
5V
C2
C1
Vdd
MCU
CAN
MODULE
Vss
D1
C4
C3
VBAT
INH
VDD
EN
STB
NERR
WAKE
RTH
CANH
CANL
TX
RX
MC33388D
RTL
GND
R1
CAN BUS
Component information:
C1>= 47nF
C2>= 4.7uF
C3>= 47nF
C4>= 10uF
D1: 1N4148
R1=R2=R (500Ω<R<16kΩ)
R / number of nodes>100Ω
R2
MC33388
MOTOROLA
12