Recent Posts

1

Repair / Re: Please help, how can I adjust this transistor?

« Last post by daisizhou on Today at 11:59:15 am »

You mean I disconnected the 8920a input?
In other words, the 8920a input is left floating,Then use a multimeter to measure the voltage value in the picture above, right?

2

Beginners / Re: Reducing ripple voltage in 2 MCU circuit

« Last post by selcuk on Today at 11:57:16 am »

The inductances of 3.3V and GND nets may cause an issue. You can short F1 to see its effect. Additionally you can use a star connection for GND net going to the MCUs. Is 3.3V net going through a single via?

3

Repair / Re: Please help, how can I adjust this transistor?

« Last post by Harry_22 on Today at 11:53:52 am »

Could you measure the following points by multimeter not oscilloscope.
Be careful and don't short the pins with the transistor case.

We don't need the generator any more.

4

Projects, Designs, and Technical Stuff / Re: Anyone familiar with LEA-M8F?

« Last post by Solder_Junkie on Today at 11:51:06 am »

I use a TinyPFA phase frequency analyser, you can also load alternative firmware into a NanoVNA H4 and use it as a PFA (and swap back again to VNA firmware).

I have three GPSDOs, 2 home made (Lars Walenius and G3RUH type), and a Leo Bodnar GPSDO (uses a TCXO and navigation grade GNSS module). My rubidium is an Efratom FRS-C that is ex cellular use, it was a gift from an electronic surplus dealer.

Of my four "standards", the poorest stability one is the Leo Bodnar, but oddly enough it is the one that I use the most as it is almost instantly stable within a few seconds from switch-on and can output any frequency up to 800 MHz. It can also be powered from USB, so consumes very little power.

SJ

5

Microcontrollers / Re: Additional high res. PWMs by using Configurable Logic Cell (CLC) block?

« Last post by JPortici on Today at 11:45:27 am »

Hi,
check the device datasheet. You can't use just any peripheral signal with CLC (see the CLCxSEL register!)
Altough, it might be possible to take one of the HSPWM with PPS output and route to CLCINx via virtual connections, but i don't have a device at hand to test if it works. Even if it worked, only PWM4 can be routed through PPS in the dsPIC33CK2556MP508 family.
I couldn't find timing specifications for the CLC, so additional delays are not characterized.

If you can live with some channel at lower frequency PWM, remember that you have 8 pair of HSPWM + 1 MCCP (which can do full bridge/deadtime) + 8 SCCP (which require CLC trickery to achieve full bridge/deadtime)

6

Beginners / Re: Component identification help

« Last post by gamalot on Today at 11:43:41 am »

Thanks for that, i think you are mostly correct.

Not sure about the .85v voltage reg, see attached picture.

In my opinion it is a MC74HC1G04.

https://www.onsemi.com/pdf/datasheet/mc74hc1g04-d.pdf

7

Test Equipment / Re: Siglent SDS800X HD Review & Demonstration Thread

« Last post by mawyatt on Today at 11:42:56 am »

Digital summation with a math function does, of course, not introduce any IMD between the two signals. You just get the sum of the two (complex) spectra, since FFT(x+y) = FFT(x) + FFT(y).

Exactly!! The separate channel digitized signals can't "see" each other, thus no IMD should be present and why we mentioned such.

Best,

8

Beginners / Re: Reducing ripple voltage in 2 MCU circuit

« Last post by doru.cazan on Today at 11:35:46 am »

Thanks @tszaboo,
Here are the details of the buck converter (attached images). There is a 4 layers board and tried to design the PCB as close as possible to the data-sheet recommendation. The components values are the ones from WEBENCH® POWER DESIGNER with the difference that I doubled the input and output ceramic capacitors (10uF and 100uF)-orange rectangle. The low power MCU is an AVR, it will run at 10Mhz and there are 10uF, 1uF and 0.1uF capacitors very near it so probably it is fine; the second MCU is and esp32-s3 and about 200mV ripple is, I think, dangerously close to the 3V lowest power requirement for it... if possible I would like to reduce the ripple and I do not mind adding the LDOs if those will help: it is a hobby project so the cost for one board is not relevant in this case. it is just that I am not sure if adding LDOs it will really help reducing the ripple...
I can also test it with an electrolytic cap but there are already 2 x 100uF ceramic caps in parallel for the 3.3V output voltage and the enclosure will be really thin; not sure how many uF I can squeeze inside (height from the PCB to the enclosure is about 7mm)  Oh! I would like to avoid tantalum caps if possible.

9

Projects, Designs, and Technical Stuff / Re: Anyone familiar with LEA-M8F?

« Last post by SCSKITS on Today at 11:35:12 am »

SJ:

The plots were made against an HP Z3801 GPSDO.
I also have a couple Rubidium oscillators, but have to permanently install them so they can run for a while before use.
For my purposes, the PLL type GPSDO is adequate.

What do you use for a Phase/frequency analyzer?

ed

10

Metrology / Re: LM399 based 10 V reference

« Last post by Birb on Today at 11:32:33 am »

Oh, ok. Thanks!