Supply voltage:
ProgRock2 current consumption is approximately 30-35 mA. It does vary a little depending on
Si5351A output loading, the configured outputs and their frequency.
The MIC5219 datasheet specifications for voltage and power dissipation need to be observed.
According to the MIC5219 datasheet the input voltage range, for a 3.3 V 50 mA output is +3.5 to
+12 V.
At a +12 V supply and 30 mA current consumption the power dissipation in the voltage regulator
will be 261 mW. According to the MIC5219
datasheet this level of power dissipation is
acceptable. Therefore even a +12V supply may be
used. However, 261 mW is quite a lot of power
dissipation (and hence heating) so you may wish to
bear that in mind and use a lower supply voltage if
possible.
The minimum acceptable supply voltage is
determined by the dropout voltage graph in the
MIC5219 datasheet which for 30mA load is approx
100mV. I’d suggest allowing a little safety margin
and supply ProgRock2 with at least 3.5V.
Care should be taken when powering ProgRock2
directly from the USB cable (see below), and using a power supply connected to +V at the same
time. The USB cable +5V will power ProgRock2 via an onboard diode, resulting in about 4.4V
supply to ProgRock2. If you have connected an additional external supply voltage to ProgRock2,
and that is less than 4.4V, then your external supply will fight with the USB voltage, potentially
drawing excessive current through the onboard diode.
3.3V output
The regulated 3.3V output from the onboard voltage regulator is provided on one of the pads. If
you use this, please be sure to observe all MIC5219 datasheet specifications regarding loading
etc.
Bank selection
Bank selection inputs BANK 0, BANK 1 and BANK 2 may be used to select one of 8 banks of
three frequencies programmed into the module. They have internally activated pull-up resistors.
To activate a BANK input, it should be grounded.
For example, if you want to select bank 5: ground the BANK 0 and BANK 2 inputs (4 + 1 = 5).
If the BANK pins are left unconnected, bank 0 is active by default.
Note that these processor I/O pins should not be connected to a voltage higher than 3.3V.
ProgRock2 manual 1.00b
6
