New Bipolar Boost TX and Front End

[waltr]

Looks great JL.
I like the single board, it makes the project look a bit simpler.
Also like having a connector to bring in all timing signals from the 'digital/control' board.

One thing I seem to see that might be an issue.
The ADC (LT237 ADC_REF cap (C51) needs to be very close to the ADC's ref pin 8 and ground.
We are using this ADC where I work and I found that there is a good current draw when the ADC starts acquisition (charging it's S&H cap).
This caused a huge error on the ADC value.

Also, 100nF is NOT enough C on this pin. Data sheet suggests 47uF, low ESR and we used a 100uF, 1206/1210 size.
Kemet C1210C107M8PACTU - Digikey #399-11631-1-ND
or Samsung CL32A107MPVNNNE - Digikey #1276-3364-1-ND

[Mdtoday]

Very nice work JL! I like it a lot.

@KingJL, I will go over the files today and have a first run check and report back

[KingJL]

One thing I seem to see that might be an issue.
The ADC (LT237 ADC_REF cap (C51) needs to be very close to the ADC's ref pin 8 and ground.
We are using this ADC where I work and I found that there is a good current draw when the ADC starts acquisition (charging it's S&H cap).
This caused a huge error on the ADC value.

Also, 100nF is NOT enough C on this pin. Data sheet suggests 47uF, low ESR and we used a 100uF, 1206/1210 size.
Kemet C1210C107M8PACTU - Digikey #399-11631-1-ND
or Samsung CL32A107MPVNNNE - Digikey #1276-3364-1-ND

There are two caps on that net ... 100n (C51) for short transients and a 47u (C55) for the surge.

[KingJL]

@KingJL, I will go over the files today and have a first run check and report back

I have already discovered (and corrected) 3 instances of REF's overlaping or too close to be easily read.

[Mdtoday]

I have already discovered (and corrected) 3 instances of REF's overlaping or too close to be easily read.

Thanks for the heads up JL

[KingJL]

Thanks for the heads up JL

I have also switched the LDO used for U1 from the LM317 to a AP2204K-ADJ. There is no need for 1.5A regulation, has a smaller footprint (SOT-23-5) and is readily available from LCSC and Mouser. After you have a chance to identify anything else, I will redo the gerbers and repost an updated Kicad archive.

[Mdtoday]

I have also switched the LDO used for U1 from the LM317 to a AP2204K-ADJ. There is no need for 1.5A regulation, has a smaller footprint (SOT-23-5) and is readily available from LCSC and Mouser. After you have a chance to identify anything else, I will redo the gerbers and repost an updated Kicad archive.

Great idea to swap to the AP2204k-ADJ

Looking at the ADC external reference and 2.5v regulator, even though its a bit of work, I would be inclined to either transpose U16/U14 circuit positions or shuffle U16/C55 to the right to get the ref circuit as close to ADC as possible.
I'll keep checking but it is looks very good, nice job.

[KingJL]

... or shuffle U16/C55 to the right to get the ref circuit as close to ADC as possible...

That I can probably do... I have to watch thoigh, the input voltage to U16 is the ~5.4V, not the Vcc going to U14.

[KingJL]

That I can probably do... I have to watch thoigh, the input voltage to U16 is the ~5.4V, not the Vcc going to U14.

Moved U16/C55to the right 2.4mm and down (toward the CMOD socket) 1.5mm.

[Mdtoday]

Moved U16/C55to the right 2.4mm and down (toward the CMOD socket) 1.5mm.

That should be better, thank you.

[KingJL]

That should be better, thank you.

I think I improved it some more... moved U15 adjacent and to the right of U14 and flipped C55 to the bottom and slid it adjacent to C51. Had to play with the power plane zones a little to make everything work.

[KingJL]

That should be better, thank you.

If you don't find anything else before the AM (my time), I will post the updates in the morning... if you do, I will address what you find and then post the updates.

[Mdtoday]

If you don't find anything else before the AM (my time), I will post the updates in the morning... if you do, I will address what you find and then post the updates.

Ok, not a problem Jl, I am looking over it again at the moment.

[Mdtoday]

I think I improved it some more... moved U15 adjacent and to the right of U14 and flipped C55 to the bottom and slid it adjacent to C51. Had to play with the power plane zones a little to make everything work.

Sounds good, would have been a bit of work for you, thanks.

[waltr]

There are two caps on that net ... 100n (C51) for short transients and a 47u (C55) for the surge.

Ahh.. I see the 47uF now.

Great idea to swap to the AP2204k-ADJ

Looking at the ADC external reference and 2.5v regulator, even though its a bit of work, I would be inclined to either transpose U16/U14 circuit positions or shuffle U16/C55 to the right to get the ref circuit as close to ADC as possible.
I'll keep checking but it is looks very good, nice job.

Agree, when we used that ADC here we had enough C but it was not close enough to the ADC like you did (C55 at U16). But the ADC_REF Voltage drooped at the ADC pin.

Moved U16/C55to the right 2.4mm and down (toward the CMOD socket) 1.5mm.

That should be better.
Ideally C55 needs to be as close to the ADC pins 7 & 8 as possible. Not into ground plane but directly to ADC's ref ground (pin 8 ).

This becomes much more important when the number of ADC bits increase. Getting good performance from a 16bit ADC is hard, 20 bit ADC is harder still.
20 bit ADC is only 7.8uV per bit.