5v to 3.3 quality and fast step down part
- Thread starter anbolge
- Start date
currently I am used TL431 with adjustable resistor and it seems to be working, however sometimes during setup procedure of teensy my veml3300 light sensor does not get recognized. But for example when i use TL431 for interrupts, in this case it seems to be working absolutely fine and takes up 7 mhz signal and brings from 5v to 3v.
PaulStoffregen
Well-known member
Difficult to answer without a bit more context. Is this power, or digital signal, or analog signal?
For a digital signal, usually my favorite is 74LV1T125, made by both TI and Nexperia.
74LCX125 is also pretty nice. I usually reach for that one when I want hot plugging (it's guaranteed high impedance when power is off) but I believe it's also faster.
For a digital signal, usually my favorite is 74LV1T125, made by both TI and Nexperia.
74LCX125 is also pretty nice. I usually reach for that one when I want hot plugging (it's guaranteed high impedance when power is off) but I believe it's also faster.
Thank you for the quick response. Yes, i need it for digital. I have a sqaure wave generated with 5v and I am counting the pulses via interrupt, which should be 3.3v max.
if we speak through hole elements, would something like this TPS757 work ? or maybe because of the output capacitor it is not good for fast signal changes? I checked TI site, and can not find a through hole analog for 74LV1T125, are these Fixed-direction voltage translators typically small and a way to go for digital signals?
if we speak through hole elements, would something like this TPS757 work ? or maybe because of the output capacitor it is not good for fast signal changes? I checked TI site, and can not find a through hole analog for 74LV1T125, are these Fixed-direction voltage translators typically small and a way to go for digital signals?
The TL431 is a reference, not a logic level converter, its probably a 100 times too slow on the edge transitions to produce reliable clocking - go with suitable 5V tolerant logic families like 74LCX, 74LVC with strong hysteresis, the 74LVC14 hex Schmitt-trigger inverter is a common choice, but annoyingly it inverts which might or might not be a problem. Be certain to decouple any logic chips you use properly.
TPS757 would be awful - don't use a regulator as a logic component unless its powering the logic!
TPS757 would be awful - don't use a regulator as a logic component unless its powering the logic!
PaulStoffregen
Well-known member
TPS757 is meant for power supply, not digital signals.
Generally speaking, through hole and high speed don't go together. You'll end up limiting yourself to a dwindling supply of older tech and obsolete parts. But if you had to go that less-than-ideal route, maybe 74HC4050 would be worth considering, or 74HC4049 if you can deal with the signal being inverted. Digikey still has 1 part in stock which isn't "marketplace" (aka surplus dealers reselling obsolete parts). But if you check out the speed in the datasheet, be prepared for underwhelming performance and lack of 3.3V specs (but at least they do guarantee a worst case for 2V which is only about 10X slower than modern high speed parts).
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I know the spec is thru hole, but SMT is really not that hard. Reflow ovens are on ebay for even $200, get some nice solder paste and tweezers and a magnifier (wearable is nice), and stick with doable size parts, at first.
It really is worthwhile to learn the craft. As Paul says, the good stuff is SMT.
P/S i use a warming stage too, it helps when deploying the paste.
It really is worthwhile to learn the craft. As Paul says, the good stuff is SMT.
P/S i use a warming stage too, it helps when deploying the paste.