Output Terminations For Qclk And Qref Drivers; Lvpecl Type Driver Terminations - Renesas 8V19N49 Series Manual

8V19N49x Hardware Design Guide
4.2

Output Terminations for QCLK and QREF Drivers

The output stage of the 8V19N490 QCLK drivers can be configured to an LVPECL or LVDS style driver.
4.2.1

LVPECL Type Driver Terminations

When the output is configured to an LVPECL style driver, the driver is open-emitter type and requires a pull-down
resistor for the DC current path in order for the output to switch. A standard LVPECL driver termination is
displayed in Figure 17. There are many ways to terminate the LVEPCL driver.
examples of LVPECL style driver termination.
R31UH0005EU0100 Rev.1.0
Jun 3, 2021
VCC=3.3V
Zo = 50
Zo = 50
LVPECL Driv er
VTT=VCC-2V=1.3
Figure 17. Standard LVEPCL 750mV Driver Termination
VCC=3.3V
Zo = 50
Zo = 50
LVPECL Driv er
Figure 18. LVPECL 750mV Termination Example 1
Figure 18
VCC=3.3V
CLK
nCLK
High Input Impedance
R2 R4
50 50
VTT
VCC=3.3V
VCC=3.3V
R1 R3
133 133
CLK
nCLK
High Input Impedance
R2 R4
82.5 82.5
to Figure 21 show several
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