Industry-Standard High-Speed CAN

Transceivers with ±80V Fault Protection

12

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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

120

Ω 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-

MAX13052

RXD

Ω

Ω

TRANSCEIVER 2

TRANSCEIVER 1

TRANSCEIVER 3

CANH

CANL

TXD

TWISTED PAIR

Ω

SPLIT

STUB LENGTH

KEEP AS SHORT

AS POSSIBLE

Figure 4. Multiple Receivers Connected to CAN Bus

CHARGE-CURRENT-

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

150pF

50M

Ω to 100MΩ

330k

Ω

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 5. IEC 61000-4-2 Contact Discharge ESD Test Model

tr = 0.7ns to 1ns

30ns

60ns

t

100%

90%

10%

I

Figure 6. IEC 61000-4-2 ESD Test Model Current Waveform