Hi Jebem
I suspect it is currently set to the default "00" value.
I would try to test it with a value of "11".
I had a quick look at the source code.
I think 8mA is already set there, right?
/* Configure the clk control and enable the output */
/* TODO: Check if the clk control byte needs to be updated. */
uint8_t clkControlReg = 0x0F; /* 8mA drive strength, MS0 as CLK0 source, Clock
not inverted, powered up */
if (pllSource == SI5351_PLL_B)
clkControlReg |= (1 << 5); /* Uses PLLB */
if (num == 0)
clkControlReg |= (1 << 6); /* Integer mode */
switch (output) {
case 0:
ASSERT_STATUS(write8(SI5351_REGISTER_16_CLK0_CONTROL, clkControlReg));
break;
case 1:
ASSERT_STATUS(write8(SI5351_REGISTER_17_CLK1_CONTROL, clkControlReg));
break;
case 2:
ASSERT_STATUS(write8(SI5351_REGISTER_18_CLK2_CONTROL, clkControlReg));
break;
}
Hi Aldo,
Yap, I think so.
clkControlReg = 0x0F 0b00001111
The last two binary digits D1 and D0 are set to 1, so it is already at maximum current.
One other
optimization would be to run the VDDOx pin 7 at 3.3V, but the kit you are using most probable uses that voltage already from the LDO regulator. The 3.3V are important because the IC specs states that is a condition to have the alleged Zout of 50R.
I could not read the LDO regulator reference code from your pictures to learn the output regulated voltage, but the easier way would be to use a multimeter to check the voltage at pin 1 (VDD) and pin 7 (VDDOx).
Other
additional optimization would envolve the addition of two bypass capacitors between pin 7 and GND, soldered as close as possible to the pin 7 of the Si5351 IC.
One of them should be a small capacitance, like a 100nF, with wv of 50V minimum, ceramic capacitor, to clear fast RF transients;
The other one should be a larger, electrolytic type capacitor, like a 10uF or maybe a 22uF, 105°C grade, with a wv of 25V or higher to have a low ESR, able to clear lower frequency fluctuations.
Sorry, I missed your request on the OWEN HDS272 on waveforms quality.
I would need to check the reviews to find out.
But as you found out, the OWON shapes are not exactly perfect either and even look worse on that review than what our scope here can do.
It seems that the only big issue with this scope is the
bandwidth figure changing with the vertical amplitude of the signal.
This is really annoying and a big red flag on this scope if it is confirmed to be happening due to a design flaw.
I already commented initially about this PGA (programmable gain amplifier) section in scopes.
Not all are designed in the same way, but all of them need to present an adequate signal to the ADC, not too small and not too excessively large.
This implies that the input signal needs to be amplified if it is too small, and needs to be attenuated if it is too large.
At least on these low/medium cost scopes, we see the use of
signal relays (mechanical or SS) to insert/remove RC networks to change the attenuation, depending on the selected vertical sensitivity, hence the
clicks the mechanical relays do when changing selectivity.
My 200EUR OWON SDS1102 100MHz 1GSPS does the same.
So this scope decreases the usable bandwidth when the vertical sensitivity is decreased.
This seems to be related to the insertion of a RC network in series with the input circuit in order to attenuate the input signal.
Either it is a design flaw or else a production batch using wrong/defective component values.
In both cases I hope that the manufacturer have detected and corrected the issues.
I expect to get the latest H/W revision (v9.15) and hope to get a good free of red flag bugs unit.
I am afraid I will not be able to test my scope when it arrives, because due to personal reasons, I am away from my home where I have lab equipment, and I will not return before December.
Here at my mother's house I have just a LCR, a couple of multimeters, a small lab power supply and the usual tools including an soldering iron. I would need a proper RF signal generator and another scope.
Meanwhile, I will use my new scope to help on the repair of a few vintage PLL double conversion heterodyne radios in my collection, starting with a pair of Grundig Satellit 500.