General Physical Layer Requirements Section 1 Introduction
16 9ARD000015-600
General Physical Layer Requirements
Table 1 lists the specifications for the physical layer.
Table 1. Physical Layer Specifications
General Characteristics Specifications
Bit rates 125 K, 250 K, 500 K
Distance with thick trunk 500 m at 125 kBaud
250 m at 250 kBaud
100 m at 500 kBaud
Number of nodes 64
Signaling CAN
Modulation baseband
Media Coupling Encoding NRZ with bit stuffing
Media Coupling Media Coupling DC coupled
differential Tx/Rx
Isolation
(1)
(Electric Current Limit)
Between network conductors and earth ground. Also
between network conductors and any other conductors that
are common between nodes.
Note: Network Conductors are V-, V+, CAN HI, and CAN LO
(1) This specification is intended only to prevent large loops, which can contribute to signal interference. Meeting this
requirement does not imply meeting any particular safety requirement. The vendor is responsible to determine
applicable safety standards and assuring compliance to those standards.
+/- 500 Volt DC test voltage -
maximum electric current flow = 1
milliamp (optional opto-isolators on
transceiver’s node side)
Differential input impedance typical (recessive state) Shunt C = 5 pF
Shunt R = 25 Kiloohms (power on)
Differential input impedance minimum (recessive state) Shunt C = 24 pF plus 12 pF/ft of
permanently attached dropline
Shunt R = 20 Kiloohms
Absolute maximum voltage range -25 to +18 Volts (CAN_H, CAN_L)
(2)
(2) Voltages at CAN_H and CAN_L are referenced to the transceiver IC ground pin. This voltage is higher than the
V- terminal by an amount equal to the voltage drop on the Schottky diode. The maximum voltage should not exceed 0.6 V.
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