ClockTamerFeaturesAndTechnicalSpecification

Output types
ClockTamer comes with one or more 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.

USRP users can use either CMOS or half-LVDS outputs, although CMOS is the default and 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:



Output frequencies
The output frequency can be set with 1Hz precision (this is a firmware limitation and could be fixed in later firmware versions). Tuning is possible within the following ranges:

Schematics, PCB layout and bill of materials
Schematics

Download PDF

PCB layout (click for larger version)





Bill of materials

Download XLS

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
Measured for 52MHz output.



Output waveform
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

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

Schematics, PCB layout and bill of materials
Bill of materials

Download XLS

Schematics

These are the same as ClockTamer-1.2.

PCB layout

PCB layout has only minor changes compared ClockTamer-1.2