Table of Contents

• Table of Contents
• Output types
• ClockTamer -1.2
• Specification of ClockTamer -1.2
• Output frequencies of ClockTamer -1.2
• Schematics, PCB layout and bill of materials of ClockTamer -1.2
• Phase noise of ClockTamer -1.2
• Output waveform of ClockTamer -1.2
• ClockTamer -1.1
• Specification of ClockTamer -1.1
• Output frequencies of ClockTamer -1.1
• Schematics, PCB layout and bill of materials of ClockTamer -1.1

Output types

ClockTamer comes with one or several of the following output types:

• CMOS - single-ended output, <3V peak-to-peak. The most popular option for low output frequencies (<200 MHz)
• LVDS - differential output, <0.5V peak-to-peak. Useful if you want to generate frequencies above 200 MHz. Requires correct termination of both ends of LVDS output. You cannot use one end and leave the other floating.
• "half-LVDS" - single-ended output, <0.5V peak-to-peak. In half-LVDS outputs only positive end (N+) is accessible to a user, while negative end (N-) is terminated with 50 Ohm resistor on the ClockTamer PCB. This output has the same frequency limitation as CMOS (<200 MHz), but has lower peak-to-peak voltage.

Users of USRP can use either CMOS or half-LVDS outputs, though CMOS is the default and is the most popular option.

ClockTamer-1.2

ClockTamer-1.2 with a single CMOS output and no GPS:

ClockTamer-1.2 with all outputs and GPS:

Specification of ClockTamer-1.2

Output frequencies of ClockTamer-1.2

Output frequency can be set with 1Hz precision (this is a firmware limitation and could be fixed in later firmware versions). Tunning can be done in the following ranges:

Schematics, PCB layout and bill of materials of ClockTamer-1.2

• Schematics: (pdf)
• PCB layout: top (png), bottom (png)
• Bill of materials: (xls)

Links to datasheets of the most important parts:

• Atmel ATMega (AT90USB162/AT90USB82) - (pdf)
• Connor Winfield D75A (TCXO, 10MHz/20MHz 0.28ppm) - (pdf)
• National Semiconductor LMX2531LQ1515E/LMX2531LQ2080E (PLL + fractional VCO) - (pdf)
• National Semiconductor LMK01000/LMK01010 (Clock Buffer, Divider, and Distributor) - (pdf)

Phase noise of ClockTamer-1.2

Measured for 52MHz output.

Output waveform of ClockTamer-1.2

Measurements made by Sylvain Munaut.

 USRP is modified with 51R resistor across the SMA socket on the USRP.

 Measured with a 350 MHz scope and a 4GHz active probe freshly
 calibrated with as short a ground lead as you can make.
 
 It shows a dead center 2 Vpp, low ringing, and fast enough rise time
 to meet the USRP clock chip input requirements.

Measurement for ClockTamer CMOS output

Measurement for ClockTamer single-ended LVDS output

ClockTamer-1.1

Specification of ClockTamer-1.1

Output frequencies of ClockTamer-1.1

Output frequency can be set with 1Hz precision (this is a firmware limitation and could be fixed in later firmware versions). Tunning can be done in the following ranges:

Schematics, PCB layout and bill of materials of ClockTamer-1.1

• Bill of materials: (xls)

Schematics is the same as in ClockTamer-1.2, PCB layout has only minor changes comparing to ClockTamer-1.2. Find !ClockTamer-1.2 schematics and PCB layout here.