Products > Test Equipment
Affordable <200MHz PDN analysis / impedance measurement hardware?
inevitableavoidance:
--- Quote from: Smokey on November 12, 2024, 09:10:50 pm ---
--- Quote from: inevitableavoidance on October 28, 2024, 02:57:41 pm ---...
Here's the board measuring a low impedance capacitor array:
...
--- End quote ---
what is that capacitor board??? I gots to know! purpose, total capacitance, how the hell did they place/solder all those caps when they are damn near touching??
--- End quote ---
Hehe, I wondered when someone would scratch their head about those. I had them made a while ago for both fun (they spot weld) and for those occasions where someone says “maybe we can solve it by adding more capacitors”. There’s a total of 6960 10V 10uF 0603 capacitors on there - cheapest I could find per uF - adding up to around 70mF, with a negligible ESR (limited by the 35oz copper planes) and an ESL limited by the wires you solder on there. Works great at eradicating supply ripple if it’s within the right bandwidth. I also have some stacked together with bismuth solder. :)
The alternating rows of capacitors are flipped in polarity, so the ends nearly contacting other ends are all the same net. Placement is done with tiny vacuum nozzles, soldering with solder paste and a reflow oven.
inevitableavoidance:
--- Quote from: joeqsmith on November 12, 2024, 09:29:08 pm ---In the manual, I show measuring my standards using my old HP network analyzer at 2.5kHz. The 0.1 ohm standard had 2.74% error without the common mode transformer. With it, 0.54%. I could repeat this at higher frequencies but it will only get worse. I could also attempt it with my H4 with / without transformer. I doubt it would meet your requirements with a direct connection.
--- End quote ---
Hmm, shit, I blindly hoped it would stay the same regardless of frequency. I’ll start cooking up a board for that differential amplifier.
tszaboo:
--- Quote from: inevitableavoidance on November 12, 2024, 09:32:03 pm ---
--- Quote from: Smokey on November 12, 2024, 09:10:50 pm ---
--- Quote from: inevitableavoidance on October 28, 2024, 02:57:41 pm ---...
Here's the board measuring a low impedance capacitor array:
...
--- End quote ---
what is that capacitor board??? I gots to know! purpose, total capacitance, how the hell did they place/solder all those caps when they are damn near touching??
--- End quote ---
Hehe, I wondered when someone would scratch their head about those. I had them made a while ago for both fun (they spot weld) and for those occasions where someone says “maybe we can solve it by adding more capacitors”. There’s a total of 6960 10V 10uF 0603 capacitors on there - cheapest I could find per uF - adding up to around 70mF, with a negligible ESR (limited by the 35oz copper planes) and an ESL limited by the wires you solder on there. Works great at eradicating supply ripple if it’s within the right bandwidth. I also have some stacked together with bismuth solder. :)
The alternating rows of capacitors are flipped in polarity, so the ends nearly contacting other ends are all the same net. Placement is done with tiny vacuum nozzles, soldering with solder paste and a reflow oven.
--- End quote ---
I think everyone had the idea of just using a lot of capacitors, but you took this to a new level.
Your circuit is quite interesting. Any reason you decided to AC couple the signals instead of accepting the small DC offsets?
rhb:
An HPAK 4395A is reasonably priced and had a very long life, so plentiful. I’m using one to develop EMI filters to suppress conducted noise from my LED shop lighting.
It will really get a workout when I start building the screen room feeds.
I really can’t see how you can improve on the price - performance. I love it. Best possible tool for the frequency range of interest. It’s both a VNA and an SA with 1 Hz resolution. It covers 10 Hz to 500 MHz. For HF work it’s the king.
Designing appropriate fixtures and calibration standards for testing boards won’t be easy. You’ll need machine tool access. Helps a lot if you design in test points. Low impedance fixtures are likely to be “interesting” to make. But then the challenge is the whole point for a lot of projects.
Have Fun!
Reg
inevitableavoidance:
--- Quote from: tszaboo on November 12, 2024, 09:59:02 pm ---Your circuit is quite interesting. Any reason you decided to AC couple the signals instead of accepting the small DC offsets?
--- End quote ---
Thanks! When for example measuring the output impedance of a buck converter under load the DC bias will be equal to the output voltage, so for measurements like this being able to handle high DC offsets is essential
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