SNAU210B March   2020  – July 2021

 

  1.   Trademarks
  2. 1Evaluation Board Setup
  3. 2EVM Description
    1. 2.1 Installing the Software
  4. 3Bringing LMX2594 to a Lock State
  5. 4Loop Filter Configuration
  6. 5Key Results to Expect
  7.   A Schematic
  8.   B Bill of Materials
  9.   C Board Layers Stack-Up
  10.   D Changing Reference Oscillator and Setup
  11.   E Connecting Reference Pro
  12.   F Ramping Feature
  13.   G SYSREF Feature
  14.   H Enabling Onboard DC-DC Buck Converter (TPS62150)
  15.   Revision History

E Connecting Reference Pro

To use Reference Pro, change the configuration for SE or differential connection as shown on Section D.

GUID-0448E5EB-AEBC-4AD9-B5E5-8EB0FA486881-low.gif Figure E-1 LMX2594EVM Setup With Reference Pro

The LMK61PD0A2 has several control pins dedicated for output format control, output frequency control, and output enable control. These control pins can be configured through the jumpers shown in Table E-1 and Table E-2.

Jumpers FS1, FS0, OS, and OE can be used to configure the corresponding control pin to either high or low state by strapping the center pin to VDD position (tie pins 2-3) or GND position (tie pins 1-2), respectively. Connections from the VDD position to the device supply or from the GND position to the ground plane are connected by 1.5-kΩ resistors.

Table E-1 Output Frequency of LMK61PD0A2 (Reference Pro)
FS1 FS0 OUTPUT FREQUENCY (MHz)
0 0 100
0 NC 312.5
0 1 125
NC 0 106.25
NC NC 156.25
NC 1 212.5
1 0 62.5
Table E-2 Output Type of LMK61PD0A2 (Reference Pro)
OS OE OUTPUT TYPE
X O Disabled (PLL Functional)
0 1 LVPECL
NC 1 LVDS
1 1 HCSL

The OS pin is used to bias internal drivers and change the output type. It is imperative to match the output termination passive components as shown on Table E-3 with the output type from Table E-2.

Table E-3 lists component values for each configuration.

Table E-3 Output Termination Schemes
OUTPUT FORMAT COUPLING COMPONENT VALUE
LVPECL AC
(default EVM configuration)		 R25, R28 0 Ω
R26, R29 150 Ω
C24, C25 0.01 µF
R27, R30, R31 DNP
DC(1) R25, R28, C24, C25 0 Ω
R26, R29, R27, R30, R31 DNP
LVDS(2) AC R25, R28, R27, R30 0 Ω
R31 100 Ω
C24, C25 0.01 µF
R26, R29 DNP
DC R25, R27, R28, R30, C24, C25 0 Ω
R31 100 Ω
R26, R29 DNP
HCSL AC R25, R28 0 Ω
R26, R29 50 Ω
C24, C25 0 Ω
R27, R30, R31 DNP
DC R25, R28 0 Ω
R26, R29 50 Ω
C24, C25 0.01 µF
R27. R30, R31 DNP
(1) 50 Ω to VCC – 2-V termination is required on receiver.
(2) 100-Ω differential termination (R31) is provided on Reference Pro PCB. Removing the differential termination on the EVM is possible if the differential termination is available on the receiver.
GUID-05519C28-099A-4299-9AC5-5C1F853354F1-low.png Figure E-2 LMK61PD0A2 Output Termination