MAX13051
±80V Fault-Protected Can Transceiver
with Autobaud
10
Maxim Integrated
The CANH and CANL common-mode range is ±12V
exceeding the ISO 11898 specification at -2V to +7V.
RXD is logic-high when CANH and CANL are shorted
or undriven.
Driver Output Protection
The MAX13051 current-limiting feature protects the
transmitter output stage against a short circuit to a posi-
tive and negative battery voltage. Although the power
dissipation increases during this fault condition, current-
limit protection prevents destruction of the transmitter
output stage. Upon removal of a short, the MAX13051
resumes normal operation.
Thermal Shutdown
If the junction temperature exceeds +165°C, the device
is switched off. The hysteresis is approximately 13°C,
disabling thermal shutdown once the temperature
drops below 152°C. In thermal shutdown, CANH and
CANL go recessive. After a thermal-shutdown event,
the MAX13051 resumes normal operation when the
junction temperature drops below the thermal-shut-
down hysteresis, and upon the MAX13051 detecting a
rising edge at TXD.
Applications Information
Reduced EMI and Reflections
In slope-control mode, the CANH and CANL outputs
are slew-rate limited, minimizing high-frequency EMI,
and reducing reflections caused by improperly termi-
nated cables.
In multidrop CAN applications, it is important to main-
tain a direct point-to-point wiring scheme. A single pair
of wires should connect each element of the CAN bus,
and the two ends of the bus should be terminated with
120Ω resistors, see Figure 6. A star configuration
should never be used.
Any deviation from the point-to-point wiring scheme
creates a stub. The high-speed edge of the CAN data
on a stub can create reflections back down the bus.
These reflections can cause data errors by eroding the
noise margin of the system.
Although stubs are unavoidable in a multidrop system,
care should be taken to keep these stubs as small as
possible, especially in high-speed mode. In slope-con-
trol mode, the requirements are not as rigorous, but
stub length should still be minimized.
Layout Consideration
CANH and CANL are differential signals and steps
should be taken to insure equivalent parasitic capaci-
tance. Place the resistor at RS as close as possible to
the MAX13051 to minimize any possible noise coupling
at the input.
