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:

Specifications

Output clock temperature stability	0.28ppm in 0-70C temperature range (without GPS option) or 50ppb with GPS option
Outputs	up to 2 CMOS outputs up to 5 LVDS outputs (default is 1 CMOS and 0 LVDS outputs)
Output connector type	U.FL
Input power voltage	3.7 - 6.0V
Input power types	miniUSB (enough to power !ClockTamer with 1 or 2 outputs with or without GPS) or 6V 2-pin connector (it has 2 connectors to connect into daisy-chain with USRP fan)
Surge protection	6V power input is protected with fast acting resetable fuse
Size	35mm x 86mm x 14mm
Control	miniUSB and SPI (16-pin connector for easy connection to USRP)

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:

	CMOS	LVDS/LVPECL
3.75 - 94.75 MHz	X	X
95.20 - 113.70 MHz	X	X
119.00 - 142.13 MHz	X	X
158.67 - 189.50 MHz	X	X
238.00 - 284.25 MHz		X
476.00 - 568.50 MHz		X
952.00 - 1137.00 MHz		X

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

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ClockTamer-1.1

Specifications

Output clock temperature stability	0.28ppm in 0-70C temperature range (without GPS option) or 50ppb with GPS sync option
Outputs	up to 2 CMOS outputs up to 3 LVPECL/LVCMOS outputs up to 2 LVDS outputs (default is 1 CMOS, 0 LVPECL/LVCMOS and 0 LVDS outputs)
Output connector type	U.FL
Power	miniUSB or 6V 2-pin connector (2 inputs to connect into daisy-chain with USRP fan)
Surge protection	6V power input is protected with fast acting resetable fuse
Size	35mm x 86mm x 14mm
Control	miniUSB and SPI (16-pin connector for easy connection to USRP)

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:

	CMOS	LVDS/LVPECL
1.42 - 32.92 MHz	X	X
32.95 - 35.91 MHz	X	X
36.25 - 39.50 MHz	X	X
40.28 - 43.89 MHz	X	X
45.31 - 49.38 MHz	X	X
51.79 - 56.43 MHz	X	X
60.42 - 65.83 MHz	X	X
72.50 - 79.00 MHz	X	X
90.63 - 98.75 MHz	X	X
120.83 - 131.67 MHz	X	X

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