prescaler OnSemi MC12080

This PCB is some kind of evaluation board for the OnSemi MC12080. This is a programmable prescaler with divisions of 10,20,40, and 80. The chip is supposed to work up to 1.1 GHz.

This PCB is intended to be used to scale down a beat note to a more usable frequency range. In specific to be measured after downscaling by a RedPitaya, which is then used for offset locking.

The logic inputs for divisor selection is optional. It can also be used in a fixed mode by soldering resistors selectively.

first tests show that it works for up to 1 GHz (for now the largest frequency tested) and divisions of 80. More will follow.

tested for div = 80 (logic: 3x Low):

notes:
* with $R_L = 820 Ohm$ and $C_L = 10p$ there is not the full 1.2V output swing (ca 900 mV). Maybe changing the load helps.
** start of decreasing output swing

Beginn des Projekts: März 2018

prototype in testing phase
effort for reproduction: 3 PCBs left, MC12080 needs to be ordered

Christian Meiners, meiners@iqo.uni-hannover.de

VLBAI

The schematic is based on the testing circuit given in the datasheet. The logic input is based on a triple schmitt trigger, to (if necessary) convert from 3.3 V to 5 V logic. The power supply is expected to be 5 V and is filtered onboard.

• schematic in PDF-format
• the source is created via KiCad and can be found on the git server: https://git.iqo.uni-hannover.de/vlbai/prescaler.git

• Size: 43 x 22 mm
• Supply: +5V
• Logic; 3x 3.3 V or 5V optional
• Eingang: SMA, up to 1.1 GHz
• Ausgang: SMA $ f_{out} = f_{in} / div $ (1.1 GHz / 10 = 110 MHz max)
• Der Bestückungsdruck: start_layout.pdf
• Die Bestückungsliste: start_bom.pdf, start_bom.xls
• zipped gerber files for PCB ordering
• Die Source des Layouts im pcb-Format liegt auf der Download-Seite des Wiki.

Was für die nächste Version zu tun ist: (: verworfen, : in Arbeit, : im Schaltplan, aber noch nicht im Layout, : erledigt)

• there seems to be a DC offset on the output. maybe a highpass on the output would be nice to get rid of it.