Power Supply

Due to the various odd voltages required by RF stages, there are no less than 4 rails:

1. 3.3V for digital/analog wave generation
2. 5V for RF gain stage
3. 12V for VCO power
4. 20-28V for VCO tuning
5. If you're using the PLL tuning system, there's an additional 2.5V rail (in the PLL section). grr!

• You should adjust the 24V boost converter to be .5V higher than the Vtune_max of the VCOs you're using to conserve power and reduce the chance of messing up the VCO
• Winding your own inductors isnt necessary but if you want to save some $ and you have magnet wire hanging around, go for it.
• Pick R1/R2 to make a voltage divider for your battery input so that the low battery input = 1.1V. You might want to use 1% resistors or measure the 5% ones to get as close as possible.
• If you're using 5V VCOs, you can power it from the gain stage converter or, alternately, cut the input trace and tie it to the battery input (~3.7V) and tie the select line low. This will change it to a 5V boost.
• The power supply is rather expensive if you're buying the boost converters. Useful input as to how this can be remedied is appreciated. Currently it seems like some sort of hand-wound multi-tap transformer and a Simple Switcher might be the easiest way.
• Dont place C20, the datasheet suggests it but it seems to make things worse (?)

* Can be sampled for free at low quantities

coming soon…