exxos's Atari, Amiga & retro forum

exxos wrote: 12 Nov 2018 00:27 http://www.ti.com/product/TPS3808/technicaldocuments

Looks good.. But output drive seems a bit wimpy :roll:

I guess a small MOSFET could be used to beaf it up.. Still smaller than a TTL chip..

Did you look at these https://www.st.com/en/reset-and-supervi ... m1816.html

Icky wrote: 12 Nov 2018 07:03 Did you look at these https://www.st.com/en/reset-and-supervi ... m1816.html

That looks cool as well. I only had a quick look at TI so far..

I am thinking though that a programmable delay time might be better as I don't actually know what the reset time is of the ST... 0.2s might be fine, though I was thinking of more like 0.5 second.

https://www.mouser.co.uk/datasheet/2/38 ... 250874.pdf


https://www.mouser.co.uk/ProductDetail/ ... 2bx6HAI%3d

MIC6315 - cheapest one in mouser... 200ms delay, manual reset, 20mA seems about as good as anything gets...

This wouldn't technically need the external buffers, my only slight concern is that there is RESET & HALT which are actually two different signals which need to be driven independently.. This could be done with 2 diodes.. Or I guess use 2 logic level MOSFETs to do the actual switching independently... Or we could just use two of these chips..

Logic level MOSFETs would have been my first choice, but the problem is this is a additional part... If we were going to have additional parts anyway, it would make sense to just use two of these chips then it is only actually one part, and buying more one part generally gets better price breaks.

It would have been nice just to have done this all in one part, but it does do away with the external buffering, so it wouldn't really be any more expensive in using two chips, but the footprint is obviously a lot smaller and of course is just one single part..

I will have a look and see if there is anything else, there are chips which have multiple monitoring inputs, so one of those might be better suited....

EDIT:

I'd say this one is the best candidate to try next...

https://uk.farnell.com/microchip/mic631 ... st=MIC6315

Even though I detest evil bay....

https://www.ebay.co.uk/itm/5pcs-SOT-143 ... :rk:1:pf:0

It would be far quicker to obtain these than wait for them to come from a pcb fab house for a month...

exxos wrote: 12 Nov 2018 14:08

EDIT:
I'd say this one is the best candidate to try next...

https://uk.farnell.com/microchip/mic631 ... st=MIC6315

Even though I detest evil bay....

https://www.ebay.co.uk/itm/5pcs-SOT-143 ... :rk:1:pf:0

It would be far quicker to obtain these than wait for them to come from a pcb fab house for a month...

Challenge accepted

Icky wrote: 12 Nov 2018 19:19
Challenge accepted

:dualthumbup:

exxos wrote: 12 Nov 2018 19:47

Icky wrote: 12 Nov 2018 19:19
Challenge accepted

:dualthumbup:

Step one of challenge get the boards - tick

Icky wrote: 14 Nov 2018 23:20 Step one of challenge get the boards - tick

:dualthumbup:

I rebuilt the original reset circuit as a hack to leave the reset circuit part of the board empty ready for testing the new reset chip.

Thought I would just share the ugliness of my hack that allows me to boot and reset. Made even the more ugly as I had to use lead free solder.

However it works and I can pull the chip out to test.

9 out of 10 for ugliness, some of those connections look far too well soldered for a 10.

Icky wrote: 16 Nov 2018 14:49 I rebuilt the original reset circuit as a hack to leave the reset circuit part of the board empty ready for testing the new reset chip.

Thought I would just share the ugliness of my hack that allows me to boot and reset. Made even the more ugly as I had to use lead free solder.

However it works and I can pull the chip out to test.


IMG_3288.png

Man if that was a Joe Master cap in the center it would look like a blue beatle being eaten by ants!! :) :) :)