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©2019-2023 Renesas Electronics Corporation

R31DS0029EU0601 September 13, 2023

XF Datasheet

Recommended Termination for HCSL Outputs

Figure 11 is the recommended source termination for applications where the driver and receiver will be on a separate PCBs. This

termination is the standard for PCI Express™ and HCSL output types. All traces should be 50Ω impedance single-ended or 100Ω

differential. Figure 12 is the recommended termination for applications where a point-to-point connection can be used. A point-to-point

connection contains both the driver and the receiver on the same PCB. With a matched termination at the receiver, transmission-line

reflections will be minimized. In addition, a series resistor (Rs) at the driver offers flexibility and can help dampen unwanted reflections.

The optional resistor can range from 0Ω to 33Ω. All traces should be 50Ω impedance single-ended or 100Ω differential.

Figure 11. Recommended Source Termination (where the driver and receiver will be on separate PCBs)

Figure 12. Recommended Termination (where a point-to-point connection can be used)

CML Termination

Figure 13 shows an example of the termination for a CML driver. In this example, the transmission line characteristic impedance is 50Ω.

The R1 and R2 50Ω matched load terminations are pulled up to VDDO. The matched loads are located close to the receiver.

Figure 13. CML Termination Example

0-0.2"

PCI Expres s

L1

L1

1-14"

Driver

Rs

0.5" Max

L3

L4

L2

L2

49.9 +/- 5%

22 to 33 +/-5%

Rt

L3

L4

L5

0.5 - 3.5"

L5

Connector

PCI Expres s

Add-in Card

PCI Expres s

0-0.2"

PCI Expres s

0-0.2"

0-18"

L1

L1

Rs

Driver

0.5" Max

L3

L3

L2

L2

49.9 +/- 5%

0 to 33

0 to 33

Rt

CML Driv er

Zo = 50

Zo = 50

R1

50

R2

50

VDDO

VDDO