FN8862 Rev.1.00

Page 21 of 27

Jul 27, 2017

ISL72027ASEH

4. Functional Description

4.5

Listen Mode

When a high level is applied to the RS pin, the device enters a low power Listen mode. The driver of the transceiver

is switched off to conserve power while the receiver remains active. In Listen mode, the transceiver draws 2mA

(maximum) of current.

A low level on the RS pin brings the device back to normal operation.

4.6

Using 3.3V Devices in 5V Systems

The differential voltages and recessive common-mode outputs are the same for both the 3.3V and 5V devices. The

dominant common-mode output voltage is slightly lower than that of the 5V counterparts. The receiver

specifications for both devices are also the same. Although the electrical parameters appear compatible, perform

necessary system testing to verify interchangeable operation.

4.7

Split Mode Termination

The VREF pin provides a VCC/2 output voltage for Split mode termination. The VREF pin has the same ESD

protection, short-circuit protection, and common-mode operating range as the bus pins.

The Split mode termination technique is shown in Figure 48.

Figure 48. Split Termination

Split mode termination is used to stabilize the bus voltage at VCC/2 and prevent it from drifting to a high

common-mode voltage during periods of inactivity. The technique improves the electromagnetic compatibility of a

network. The Split mode termination is put at each end of the bus.

The CL capacitor between the two 60Ω resistors filters unwanted high frequency noise to ground. The resistors

should have a tolerance of 1% or better and the two resistors should be carefully matched to provide the most

effective EMI immunity. A typical value of CL for a high speed CAN network is 4.7nF, which generates a 3dB

point at 1.1Mbps. The capacitance value used is dependent on the signaling rate of the network.

NODE

#1

NODE

#n

CANH

CANL

VREF

VREF

CL

CL

NODE

#2

60Ω

60Ω

60Ω

60Ω