2.
Design
The ProgRock2 schematic is shown below.
This is a very simple circuit consisting of:
•
STM32 Cortex M0 CPU controller
•
Si5351A/MS5351M triple clock generator
•
25MHz 0.25ppm TCXO reference (Temperature Controlled Crystal Oscillator)
•
MIC5219 3.3V voltage regulator
•
Micro-USB connector
•
Pads for other connections
All these are SMD components, pre-assembled at the PCB factory, onto the tiny ProgRock PCB.
The Si5351A synthesizer chip is now used in many other QRP Labs products such as the QCX
CW transceiver series and QDX digital transceiver. This is a Digital Phase Locked Loop (PLL or
DPLL) synthesizer which provides three separate frequency outputs, each having a frequency
range spanning 3.5kHz to 200MHz. The frequency stability is governed by the a crystal reference.
Due to unavailability of the Si5351A, the
equivalent MS5351M may be used. For test
details on the performance of Si5351A vs
MS5351M demonstrating the suitability of the
MS5351M (in fact, slight superiority in many
regards), please see
http://qrp-labs.com/synth/ms5351m.html
The block diagram (right) is taken from the
SiLabs Si5351A datasheet. Briefly, the 27MHz
reference oscillator is multiplied up to an internal
Voltage Controlled Oscillator in the range 600-900MHz (the PLL), then divided down to produce
the final output frequency. The multiplication up and the division down are both fractional and so
the frequency resolution is extremely finely controlled. The chip has two PLLs and three output
ProgRock2 manual 1.00b
2
