Power supply notes
Due to the various odd voltages required by RF stages, there are no less than 4 rails:
- 3.3V for digital/analog wave generation
- 5V for RF gain stage
- 12V for VCO power
- 20-28V for VCO tuning
- 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 (?)
Parts List - Power supply
| Part # & Datasheets | Name |
Description | Distributor |
Qty |
Cost |
Total |
|---|---|---|---|---|---|---|
| J-188-1 | SW1 |
Alternate action push button switch | 1 |
$0.95 | $0.95 | |
IC1 |
3.3V/200mA LDO regulator | Digikey |
1 |
$0.53 |
$0.53 |
|
| *LM2733x | IC2 |
5 (or 7V) DC/DC converter | Digikey |
1 |
$2.58 |
$2.58 |
| *LT1301CS8 | IC3 |
12V DC/DC converter | Digikey |
1 |
$4.75 |
$4.75 |
| *LT1173CS8 | IC4 |
25V+ DC/DC converter | Digikey Linear |
1 |
$4.88 |
$4.88 |
| CDRH6D28NP-150NC | L1 |
15uH power inductor | 1 |
$1.03 |
$1.03 |
|
| CDRH6D28NP-330NC | L2, L3 |
33uH power inductor | 2 |
$1.03 |
$2.06 |
|
| 0.1uF 1206 ceramic capacitor | C2, C3 C7, C9, C11, C13, C16, C17 |
0.1uF ceramic filter capacitor | 8 |
$0.08 |
$0.64 |
|
| 1.0uF 1206 ceramic capacitor | C4, C6, C12, C15, C19 |
1.0uF ceramic filter capacitor | 5 |
$0.18 | $0.90 | |
| UWX0J101MCL1GB | C1 |
100uF 6.3V input filter capacitor | 1 |
$0.17 |
$0.17 |
|
| UWX0G101MCL1GB | C5 |
100uF/4V filter capacitor | 1 |
$0.17 |
$0.17 |
|
| TPSC107K010R0100 | C10 |
100uF/10V low ESR tantalum capacitor | 1 |
$1.18 |
$1.18 |
|
| TPSC686K016R0200 | C14 |
68uF/16V low ESR tantalum capacitor | 1 |
$1.44 |
$1.44 |
|
| B45197A6226K409 | C18 |
22uF/35V low ESR tantalum capacitor | 1 |
$1.40 |
$1.40 |
|
| 160pF 1206 ceramic capacitor | C20 |
feed foward capacitor for 5V regulator (do not place) | Digikey |
1 |
||
| 1206 5% resistors | R1, R2 |
Chosen value resistors for low battery detect: R1/(R1+R2)*Vlow = 1.1 | Digikey/Mouser |
2 |
$0.08 |
$0.16 |
| 120K 1206 5% resistor | R3 |
Boost voltage reference resistor for 5V | Digikey/Mouser |
1 |
$0.08 |
$0.08 |
| 12K 1206 5% resistor | R4 |
Boost voltage reference resistor for 5V | Digikey/Mouser |
1 |
$0.08 |
$0.08 |
| ~2K 5% resistor in 1206 pkg | R5 |
LED choke resistor (~1-2K depending on LED and brightness) | Digikey/Mouser |
1 |
$0.08 |
$0.08 |
| 50K 1206 resistor | R6 |
Boost voltage reference resistor for 24V | Digikey/Mouser |
1 |
$0.08 | $0.08 |
| 1Meg 1206 resistor | R7 |
Boost voltage reference resistor for 24V | Digikey/Mouser |
1 |
$0.08 | $0.08 |
SS14 (for example) |
D1-D3 |
Schottky Diode (at least 1A/20V) | 3 |
$0.30 |
$0.90 |
|
| Total | $11-$26 |
Power supply assembly
|
Get all your parts ready to solder in the 3.3V supply |
 |
Solder in the 3.3V supply, input filter caps and the power button as shown |
 |
Apply ~4V power, make sure the switch is on and test for 3.3V |
 |
Next is the 5V boost supply |
 |
Solder in all the necessary components for the boost converter. |
|
Test for 5V (here shown with a scope, a multimeter is fine too). |
 |
Next prepare to solder in the 12V boost converter. |
| needpix | Solder in 12V boost converter |
|
Verify 12V output. |
 |
Get your 28V boost supply parts |
 |
Solder in the 28V supply |
 |
Test with a meter, the actual voltage isnt so important just make sure its a little higher than your max Vtune. |
 |
You might see some noise on the boost converters |
