74HCT125 quad driver as cheap 100mA push/pull driver

[0xdeadbeef]

Instead of using the relatively expensive (~5€) Microchip TC4468 as quad push/pull driver in one of my projects I thought about replacing it with 4 cheap 74HCT125 quad drivers, where I use 4 outputs in parallel on each 74HCT125 to get 100mA combined. This would reduce the cost to <1€ for the four 100mA/50Ohm outputs. I'll add Polyfuses and 5V Transil suppressor diodes as overvoltage protection.
So is this a bad idea for a low cost 100mA (MOSFET) push/pull driver? Are there maybe more elegant solutions?

[bingo600]

Do you need the tristate ?
Else a HCT14 has 6 outputs

Often used as 1 package as driver for the other 5 , and then as a bonus it's not inverting the output.


/Bingo

[edavid]

Look again, most vendors have a maximum supply pin rating of 50-70mA for a 74HCT125.  Exceeding this can cause latchup.

[0xdeadbeef]

Look again, most vendors have a maximum supply pin rating of 50-70mA for a 74HCT125.  Exceeding this can cause latchup.

Good point. Have to check that.

@bingo600
I don't need the tristate urgently, but it is sure nice to have.
Also I could use the 74HCT365 if I wanted a hex driver. This way I'd need only 3 instead of four ICs to get the 4 channels with 100mA each. However, the 74HCT365 has a 500 mW power limitation, so I couldn't use all 6 outputs without exceeding that.
Same is true for the 74HCT14 unfortunately.

[SeanB]

Use an octal bus buffer, then you can get 2 drivers out of each chip.

[0xdeadbeef]

Yeah, but I'm not so optimistic to find one that could really deliver 200mA without dying of heat. Letting aside that latch-up issue.

[MasterOfNone]

I’ve never tried doing anything like that, and I must admit I was thinking that if one of the drivers in the package is slightly slower than the others, then it could still be pulling its output low while the others start pulling their output high. But if the outputs are connected in parallel, this would temporarily short the Power Supply.  But in reality the transition time of the devices isn’t zero so it’s unlikely that you would get a full short if this was the case anyway.

[TerminalJack505]

You might also check out the drivers for the other logic families.  The 74ACxx, 74ACTxx and 74Fxx-series buffers/drivers can usually source/sink more current than the 74HCxx/74HCTxx equivalent part.  They can be a bit more finicky, however.