Si5351 current consumption #chat

Eduard Voiculescu

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Hi guys,

I am comparing the current consumption of the Si5351 under the same conditions (same VCC, same 68 ohm load resistor, full power, unused outputs turned off, steady carrier within the 20m band, same frequency) in two software cases:
1. , which looks just about right in terms of power draw to what the U3S is having (~33mA)
2. Within the Etherkit 5351 library (, which you may be also aware of. The instructions are as follows:
  si5351.init(SI5351_CRYSTAL_LOAD_0PF, 27000000, 0); - external TCXO
  si5351.drive_strength(SI5351_CLK0, SI5351_DRIVE_8MA); - set max drive for output 0
  si5351.set_freq(1409717000ULL, SI5351_CLK0); - set frequency to 20m;PLL settings are calculated by the library
  si5351.output_enable(SI5351_CLK0, 1); - enable output 0;other are by default turned off
This yields about 43mA current draw by the Si5351 (10mA more than U3S/OE1CGS sketch).
Adding a couple of instructions to turn off the unused outputs clocks:
results in a lower current, ~ 39mA, but still about 6mA higher than U3S/OE1CGS sketch.
I suspect there is a catch, like finding the exact PLL specifications or turning off the unused PLL or anything like this, but I cannot figure it out. I'm just hoping anyone has any ideas.
Thank you,
Eduard YO3ICT

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