AMX RX

[ivconic]

I would say yes, C7 needs to be 10uF, low ESR cap. This provides current to the ADC's internal reference when the Conversion starts.
No experience with this MAX11158 but with the LT2380 we (at my work) had the reference droop during conversion. This was solved by putting a big low ESR cap (10uF) directly across the ADC's Ref to gnd pins.

Ok, clear.
Once the ADC is negotiated finally; I plan to do this in form of module. But anything I can put through-hole; I intend to put through-hole. Only what I can't; I will make it SMD.
Such big value for non polarized cap is easier to find in SMD variant. Through-hole one would occupy too much "square meters" on pcb!
Now I am only waiting clarifications on those resistors and final concensus about the ADC chip.

[ivconic]

Like I said; I "don't like" the power supply. Since all those "chips" are SMD and probably tough to solder on pcb.
Not to mention sourcing them from abroad.
So I have "better" solution, probably for my case only.
I can obtain indeed cheap and very small module:

DC-DC convertor step up 5V to +/-12V
+12V / 50mA
-12V / 30mA
Input voltage 2.8 - 5.5V
...
Futrher I can add 78L05, 79L05 and 1117-3v3 or LM337L regulators (along with bunch of caps all around) to get voltages properly.
All these as integral part of the RX&ADC module.
Sweet and easy.
If my calculatiuons are correct; ADC will consume 12mA at 500ksps, which leaves 38mA for the opamps at positive rail and 30mA at negative rail.
Question is are the 78/79L05 regulators "eats" some mA during the regulation? If yes; I bet it is insignificant value.

[ivconic]

How many "low power" modules will be there?
RX&ADC is solved by this (above).
MCU and RX will draw significant current, I suppose.
Audio output probably too.
What else? LCD... insignficant.
So, for the rest of the circuitry I also have "poor sourcing components & soldering skills man" solution too:
DC-DC StepUp regulator 4A with XL6009. Additional 7805/7905 regulators can be added too.
All the power suplies are supplied then from one set of batteries, one battery pack; made of 3 or 4 LiPo 18650 (or similar), tied in series using BMS.


- Input voltage: 3-32V
- Output voltage: 5-35V
- Max. current: 3A, up to 4A with heatsink
- Efficiency: 94 % (max) Normal efficiency at 85%
- Frequency: 400KHz
- Accuracy: ± 0,5%
- Working temp: -40° C do + 85° C
- Dimm: 43mm x 21mm x 14mm

Test refference:
- In 3V Out 12V 0.4A 4.8W - One 18650 LiPo
- In 5V Out 12V 0.8A 9.6W
- In 7.4V Out 12V 1.5A 18W - Two 18650 LiPo in series
- In 12V Out 15V 2A 30W - Three 18650 LiPo in series
- In 12V Out 16V 2A 32W
- In 12V Out 18V 1.6A 28.8W
- In 12V Out 19V 1.5A 28.5W
- In 12V Out 24V 1 A 24W

...
Let no one worry about possible noise, interference, cross-talking from this module to the rest of the device, because there won't be any.
The FelezJoo PI detector has been on the forum for a long time, it is "known" for its sensitivity even to a "sharp look"... everything bothers
it to work properly.
The smallest detail, the smallest tolerance... and that detector doesn't work properly at all... Who made it; he knows the suffering about it.
I have done it on several occasions and always powered it with this module. With the addition of a couple of "thick" elcos on the module itself.
There was no problem at all! The module did not introduce any noise to the operation of the detector. Everything worked as it should.

[ivconic]

Maybe I was wrong to post all this on this topic? I should have started a new topic with the name: "Poor sourcing components & soldering skills man AMX version"!

[Carl-NC]

R1-4: these are for a voltage-mode option, as in Tony's original circuit. Yes, non-zero values will elevate the noise.

ADC: This AFE design probably can't do any better than 84dB SNR. I like the ADC to be at least 6dB better (results in an overall 1dB SNR degradation) so 90dB min. Any of the ADCs we've talked about will work, it's a matter of sample rate, price, and availability.

My intent for this design is 100% SMT (except for the bench supply regs). Sorry, I can't do it with thru-hole. However, I am using the biggest SMT parts I can, preferably SOIC, SOT23, and 0805 passives. I think one of the supply chips may be MSOP, and the ADC (still TBD) may be as well.

The board I'm working on will combine the TX, RX-AFE, ADC, and power supplies on one board. It will include an IO interface to easily hook it up to a micro dev board for driving the TX and reading the ADC. I will start off by building the TX & AFE only, probably using the bench supply option, to test out RX responses to ground and targets in both current mode & voltage mode. This will give me the information I need to see if any ground compensation needs to be designed in. If it does not, then I can add the ADC and start grabbing data. Even if it does, I can still add the ADC and start writing code while making design changes to the circuit.

[ivconic]

R1-4: these are for a voltage-mode option, as in Tony's original circuit. Yes, non-zero values will elevate the noise.

ADC: This AFE design probably can't do any better than 84dB SNR. I like the ADC to be at least 6dB better (results in an overall 1dB SNR degradation) so 90dB min. Any of the ADCs we've talked about will work, it's a matter of sample rate, price, and availability.

My intent for this design is 100% SMT (except for the bench supply regs). Sorry, I can't do it with thru-hole. However, I am using the biggest SMT parts I can, preferably SOIC, SOT23, and 0805 passives. I think one of the supply chips may be MSOP, and the ADC (still TBD) may be as well.

The board I'm working on will combine the TX, RX-AFE, ADC, and power supplies on one board. It will include an IO interface to easily hook it up to a micro dev board for driving the TX and reading the ADC. I will start off by building the TX & AFE only, probably using the bench supply option, to test out RX responses to ground and targets in both current mode & voltage mode. This will give me the information I need to see if any ground compensation needs to be designed in. If it does not, then I can add the ADC and start grabbing data. Even if it does, I can still add the ADC and start writing code while making design changes to the circuit.

I hear you. Understand too.
Not you; I am gonna do it in through-hole variant. Probably will not be as good as SMD version, but I don't mind.
But until I start; first I have to see what I can obtain from material.

[Carl-NC]

I have settled on the ADC. I like the one Paul proposed, the LTC2338-18, because it can be driven differentially up to the full 20vpp that I'd like to use. Except for 2 pins, it is pin-compatible with the LTC family I originally considered so I will try to include connection options for either one.

[ivconic]

I have settled on the ADC. I like the one Paul proposed, the LTC2338-18, because it can be driven differentially up to the full 20vpp that I'd like to use. Except for 2 pins, it is pin-compatible with the LTC family I originally considered so I will try to include connection options for either one.

$56 in Mouser!
I can obtain it actually!
I totally forgot that my older son is "American" living in the USA.
But... the price is pfffffff....
Would be good if we could find cheaper yet adequate alternatives.

[ivconic]

Is the LTC2338CMS-18#TRPBF version the right version?
I have found that specific version at somewhat lower price.
What is the difference among dozen the same LTC2338 chips with so dramatically different prices?

[KingJL]

... The board I'm working on will combine the TX, RX-AFE, ADC, and power supplies on one board. It will include an IO interface to easily hook it up to a micro dev board for driving the TX and reading the ADC. I will start off by building the TX & AFE only, probably using the bench supply option, to test out RX responses to ground and targets in both current mode & voltage mode...

If you could, will you add adequate test points to the schematic/pcb layout to enhance the test/analysis environment? The only real downside I have experienced with SMD is my propensity to destroy otherwise functional PCB's with an errant probe slip! My preferred test point is the plated through hole type as the probe point has a secure area to rest in while my eyes wander to a scope or test meter.

[Tinkerer]

If you could, will you add adequate test points to the schematic/pcb layout to enhance the test/analysis environment? The only real downside I have experienced with SMD is my propensity to destroy otherwise functional PCB's with an errant probe slip! My preferred test point is the plated through hole type as the probe point has a secure area to rest in while my eyes wander to a scope or test meter.

https://www.aliexpress.com/item/1005...CH%21187950949

https://www.aliexpress.com/item/1005...d=NFuMFVpRAzkE

[Carl-NC]

If you could, will you add adequate test points to the schematic/pcb layout to enhance the test/analysis environment?

Yes, I always do that on my designs. If you look at the Power schematic, those rectangular boxes attached to every power rail are for test points. My preference is a 35mil (0.9mm) thru-hole for the wire-loop type as seen in Tony's first Aliexpress link. I don't like as much the SMT type (second link) because I'm always afraid of pulling them off the board.

[KingJL]

Great!!!

[Carl-NC]

Is the LTC2338CMS-18#TRPBF version the right version?

There are CMS, IMS, and HMS versions, all just different temperature grades. Any will work. TRPBF means "tape & reel" and "lead free." These also don't matter.

I will also try to support the LTC family of converters listed here. They have an almost identical pinout and you can get started for as little as $20.

[waltr]

Yes, I always do that on my designs. If you look at the Power schematic, those rectangular boxes attached to every power rail are for test points. My preference is a 35mil (0.9mm) thru-hole for the wire-loop type as seen in Tony's first Aliexpress link. I don't like as much the SMT type (second link) because I'm always afraid of pulling them off the board.

I also prefer the wire loop thru-hole test points.
We use the SMT ones on board at my work due to lower cost of assembly (can be pick-n-placed). They DO pull off the board when you snag a probe and pull. Luckly, it htypically does not pull the pad off the pcbso can be soleder back on.

We also use the pads, we call them Access Points since you can probe but not connect a probe.
They are handy for troubleshoot is densely pack areas of a board..