Detailed Description
The MAX14883E fault-protected CAN transceiver is
optimized for industrial network applications and oper-
ates from a 5V supply. The MAX14883E features a ±25V
common mode input range and is protected against
shorts up to ±60V on the CAN bus (CANH, CANL), making
it ideal for operating in harsh industrial environments.
The MAX14883E operates at the maximum high-speed
CAN data rate, allowing up to 1Mbps on small networks.
The maximum speed on large networks may be limited
by capacitive loading and other factors. Networks of up
to 17 MAX14883E transceivers can operate up to 1Mbps.
Larger networks of up to 120 MAX14883E transceivers
can operate up to data rates of 125kbps.
CANH and CANL outputs are short-circuit current-limited
and are protected against excessive power dissipation by
thermal shutdown circuitry that places the driver outputs
in a high-impedance state.
Transmitter
The transmitter converts a single-ended input signal
(TXD) from the CAN controller to differential outputs for
the bus lines (CANH, CANL). The truth table for the transmitter
and receiver is given in Table 1.
Transmitter-Dominant Timeout
The MAX14883E features a transmitter dominant timeout
(t
DOM
) that prevents erroneous CAN controllers from clamping
the bus to a dominant level by maintaining a continuous low
TXD signal. When TXD remains in the dominant state (low)
for greater than t
DOM
, the transmitter is disabled, releasing
the bus to a recessive state (Figure 4). After a dominant
timeout fault, the transmitter is re-enabled when receiving a
rising edge at TXD. The transmitter dominant timeout limits
the minimum possible data rate to 9kbps for standard CAN
protocol.
Driver Output Protection
The MAX14883E protects the transmitter output stage
against a short-circuit to a positive or negative voltage
by limiting the driver current. Thermal shutdown further
protects the MAX14883E from excessive temperatures
that may result from a short. The transmitter returns to
normal operation once the short is removed.
Receiver
The receiver reads the differential input from the bus
(CANH, CANL) and transfers this data as a single-ended
output (RXD) to the CAN controller. It consists of a
comparator that senses the difference V
DIFF
= (CANH-
CANL), with respect to an internal threshold of 0.7V. If
V
DIFF
> 0.9V, a logic-low is present on RXD. If V
DIFF
<
0.5V, a logic-high is present.
The CANH and CANL common-mode range is ±25V. RXD
is logic-high when CANH and CANL are shorted or terminated
and undriven.
Polarity Selection
A polarity select input (POL) switches the state of the
CANH and CANL drivers. Polarity selection allows for
software correction of cross-wired field cables, ensuring
that the transmitter continues to operate correctly in the
field. See Table 1 for detailed operation.
Thermal Shutdown
If the junction exceeds +160°C (typ), the device is
switched off. During thermal shutdown, CANH and CANL
are high-impedance and all IC functions are disabled.
The transmitter outputs are re-enabled and the device
resumes normal operation when the junction temperature
drops below 145°C (typ).
POL TXD TXD LOW TIME CANH CANL BUS STATE RXD
LOW LOW < t
DOM
HIGH LOW DOMINANT LOW
LOW LOW > t
DOM
V
DD
/2 V
DD
/2 RECESSIVE HIGH
LOW HIGH X V
DD
/2 V
DD
/2 RECESSIVE HIGH
HIGH LOW < t
DOM
LOW HIGH DOMINANT LOW
HIGH LOW > t
DOM
V
DD
/2 V
DD
/2 RECESSIVE HIGH
HIGH HIGH X V
DD
/2 V
DD
/2 RECESSIVE HIGH
Table 1. Transmitter and Receiver Truth Table (When Not Connected to the Bus)
MAX14883E CAN Transceiver with ±60V
Fault Protection and Selectable Polarity
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Maxim Integrated
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