74LS05 vs 74LS06

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74LS05 vs 74LS06

Post by exxos »

Just noticed the reset circuit has a LS05 which seems to be exactly the same as a LS06... only the LS06 has higher pull down current.

If anyone is bored enough, and then try a LS06 in the reset circuit instead of the LS05... Likely I will update this schematic use a LS06 instead. Basically it will reduce having to order 2 separate parts in the future..
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Re: 74LS05 vs 74LS06

Post by PhilC »

Will see if I have another one over the weekend
If it ain't broke, test it to Destruction.
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Re: 74LS05 vs 74LS06 (reducing chip count thoughts)

Post by exxos »

Still trying to figure out how to reduce the TTL chips.

Mostly there are inverters used before other inverters because of the pull down current needed. If we had a high current driver instead, we could do away with a chip almost. Though there are a couple of inverters used as well which makes it not so easy to swap :(

We actually have the LS11 on the ROM CE line, is a little waste of the chip as two gates are not used. This could probably be replaced with diodes, but then extra parts count isn't really what I want to do, and the end result of soldering pins isn't going to be much different.

Really using a GAL to do exactly what functions are needed would be a good idea. With the chips becoming harder to find, and people needing to be able to program them, the fact it would actually cause more routing around the board because everything will be going to one chip, I don't actually think that is a good idea to do.

Probably the best idea be to go with SMT tiny logic like I've used on boosters for buffers and inverters. This way we can have exactly gates we want exactly where they need to be. Plus as they are tiny chips, they take up hardly any PCB space.

The inverters on the WD1772 simply have to stop as there are a few used. This could be changed to a SMT chip to save a little space. There are some inverters used on the reset circuit as well.. This could be changed something else but it was still require a IC anyway.

There are some very high power mosfet driver chips which can push up to several amps output current either inverting or noninverting outputs. If the cost isn't silly, may look towards using those the main output drivers such as midi port etc. would save on having to have 4 inverters in two separate chips. Though some are open collector stuff so have to be careful there also.

The decoupling capacitors would likely go on the back of the PCB as a SMT part. So this would actually save a little space reduce clutter a little bit.

Also possible we could change the audio amp the normal general op amp buffer circuit. Would probably reduce the part count of fraction and make the circuit a little smaller.
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Re: 74LS05 vs 74LS06

Post by exxos »

It looks like a SN74LVC1G07 Is a good choice for a open collector buffer. The slightly higher output capability than the LS06 (inverter) at 50mA.

Some of the gates are not even used in the packages, but then twice the amount or used because of the open collector buffers are inverters, so their inputs have to be inverted also, is using twice the amount of gates for basically no reason.

So I think using the tiny logic to give just the gates we need is probably the way to go. These are rather tiny to solder, but not impossible. Ultimately the board will likely have to have more SMT parts in the future anyway.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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