I'm considering using the Si5351 as the quadrature oscillator in my receiver. I've read a lot about this part, but I'm still unsure how it will perform in practice, so I bought a breakout board to experiment with.

In order to make experimentation easy, I'm using a set-up that allows me to configure the part using Python code running on my laptop. In particular, I'm running Adafruit's Blinka and their Si5351 library on my laptop, and using a Raspberry Pi Pico running the u2if firmware to interface between the laptop and the Si5351.

Here's some code I ran as an initial test. It sets up two 100 MHz outputs that are 90 degrees out of phase:

import board
import busio
import adafruit_si5351

# Set the following environment variable when using the Pico:
# export BLINKA_U2IF=1

i2c = busio.I2C(board.SCL, board.SDA)
si5351 = adafruit_si5351.SI5351(i2c)

# 25 MHz (crystal) * 24 = 600 MHz
si5351.pll_a.configure_integer(24)

# 600 MHz / 6 = 100 MHz
si5351.clock_0.configure_integer(si5351.pll_a, 6)
si5351.clock_2.configure_integer(si5351.pll_a, 6)

# 90 degree phase offset for output 0
si5351._write_u8(165, 6)
si5351.reset_plls()

si5351.outputs_enabled = True

And here's what that looks like on the scope:

One key thing I'd like to understand is whether this part can provide the 7 dBm of power required to drive the ADE-1 mixer I plan to use. My understanding is that this figure indicates the power that the LO ought to deliver to a 50 ohm load. To measure this, I connected the breakout board to the 50 ohm input of my scope (AC coupled), and used the FFT to determine the amplitude of the oscillator's fundamental frequency, from which I calculated the power.  The output drive strength of the part can be adjusted between 4 levels (called 2, 4, 6, and 8 mA) so I repeated the measurement for each level. Here are the results:

If this is correct then it seems the part can at least deliver sufficient power. In truth, I'm not at all confident I'm doing the right thing here, but this is sufficiently promising that I'm happy to proceed.

However, one thing I know I don't understand is the choice of names given to the different drive strength levels, since I can't see how these currents correspond to e.g. the amplitude of the outputs as measured on the scope. Please leave a comment if you can help me with this!