MAX13050 Datasheet, PDF (12/20 Pages) Maxim Integrated Products – Industry-Standard High-Speed CAN Transceivers with ±80V Fault Protection

Industry-Standard High-Speed CAN
Transceivers with ±80V Fault Protection
MAX13052
CANH
TXD
R_L = 60Ω
RXD
SPLIT
R_L = 60Ω
CANL
TWISTED PAIR
STUB LENGTH
KEEP AS SHORT
AS POSSIBLE
TRANSCEIVER 1
R_L = 120Ω
TRANSCEIVER 3
TRANSCEIVER 2
Figure 4. Multiple Receivers Connected to CAN Bus
disabling thermal shutdown once the temperature
drops below +152°C. In thermal shutdown, CANH and
CANL go recessive. After a thermal-shutdown event,
the IC resumes normal operation when the junction
temperature drops below the thermal-shutdown hys-
teresis, and upon the CAN transceiver detecting a ris-
ing edge at TXD.
Applications Information
Reduced EMI and Reflections
In slope-control mode, the MAX13052’s CANH and CANL
outputs are slew-rate limited, minimizing EMI and reduc-
ing reflections caused by improperly terminated 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 4. 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-
R_C
50MΩ to 100MΩ
R_D
330kΩ
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
HIGH-
VOLTAGE
DC
SOURCE
Cs
150pF
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
Figure 5. IEC 61000-4-2 Contact Discharge ESD Test Model
I
100%
90%
10%
tr = 0.7ns to 1ns
t
30ns
60ns
Figure 6. IEC 61000-4-2 ESD Test Model Current Waveform
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