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SN65HVD257 EVM Setup and Operation for Redundant (Parallel Networks)

3.2 Using CAN Bus Load and Termination Configuration

Each bus of the EVM is populated with two 120Ω power resistors selectable via jumpers between CANH

and CANL. By using one of the resistors, the EVM may be used as a terminated end of a bus. For

electrical measurements to represent the total loading of the bus, use both 120Ω resistors in parallel to

give the standard 60Ω load for parametric measurement. The EVM also has footprints for customer

installation of split termination if the application requires it. The table below summarizes how to use these

termination options. If split termination is used, care must be taken to match the resistors. The common-

mode filter frequency may be calculated by: f

= 1 / (2 π R C). Normally, the split capacitance is in the

range of 4.7nF to 100nF. Keep in mind that this is the common-mode filter frequency, not a differential

filter that will impact the differential CAN signal directly.

Table 3. CAN Bus Termination Configuration

Split Termination CM Stabilizing

120Ω Resistors

Footprints Capacitor

"Termination Configuration Bus 1"

JMP4 JMP6 R5 R13 C3

Standard Termination (120Ω) shorted open NA NA NA

60Ω load - Electrical Parameterics shorted shorted NA NA NA

Split Termination (Common Mode

open open 60Ω 60Ω populated

Stabilization)

Split Termination CM Stabilizing

"Termination Configuration Bus 2" 120Ω Resistors

Footprints Capacitor

JMP9 JMP11 R29 R37 C23

Standard Termination (120Ω) shorted open NA NA NA

60Ω load - Electrical Parameterics shorted shorted NA NA NA

Split Termination (Common Mode

open open 60Ω 60Ω populated

Stabilization)

SLLU172–August 2012 SN65HVD257 CAN EVM: Functional Safety and Redundant CAN Network

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