Controlled Impedance Driver (Source Termination)

UltraScale Architecture SelectIO Resources User Guide (UG571)

Document ID
UG571
Release Date
2022-08-31
Revision
1.14 English

To optimize signal integrity for high-speed or high-performance applications, extra measures are required to match the output impedance of drivers to the impedance of the transmission lines and receivers. Optimally, drivers must have an output impedance matching the characteristic impedance of the driven line, otherwise reflections can occur due to discontinuities. To solve this issue, designers sometimes use external-source series-termination resistors placed close to the pins of high-strength, low-impedance drivers. The resistance values are chosen such that the sum of the output impedance of the driver plus the resistance of the source series-termination resistor roughly equals the impedance of the transmission line.

DCI can provide controlled impedance output drivers to eliminate reflections without requiring the use of an external source-termination resistor. The impedance is derived from the external reference resistor.

This Figure illustrates a controlled impedance driver inside a device.

Figure 1-9:      Controlled Impedance Driver

X-Ref Target - Figure 1-9

X16067-controlled-impedance-driver.jpg

The DCI input standards supporting the controlled impedance driver are shown in Table: All DCI I/O Standards Supporting Controlled Impedance Driver .

Table 1-2:      All DCI I/O Standards Supporting Controlled Impedance Driver 

HSTL_I_DCI

DIFF_HSTL_I_DCI

LVDCI_18

HSUL_12_DCI

DIFF_HSUL_12_DCI

SSTL18_I_DCI

DIFF_SSTL18_I_DCI

HSTL_I_DCI_18

DIFF_HSTL_I_DCI_18

LVDCI_15

POD12_DCI

DIFF_POD12_DCI

SSTL15_DCI

DIFF_SSTL15_DCI

HSTL_I_DCI_12

DIFF_HSTL_I_DCI_12

HSLVDCI_18

POD10_DCI

DIFF_POD10_DCI

SSTL135_DCI

DIFF_SSTL135_DCI

 

 

HSLVDCI_15

 

 

SSTL12_DCI

DIFF_SSTL12_DCI