3.3V to 5V voltage transceiver IC (Min 16mA) - Page 1
Forum section: electronics / projects

author: hobbyelectronics
author_rank: Regular Contributor
timestamp: August 25, 2024, 04:54:42 pm
content: Hello,Hopefully, this is a quick and easy question to answer.I need to drive a stepper driver (Stepper Online CL42T-V4.1) with a ARM MCU based controller.The DIR, ENABLE & PULSE inputs are optocoupled in the driver itself, and are 5V inputs (These do not work reliably at 3.3V, I tried it).The data sheet states the input current (For each i/p) is 10 mA typical and 16mA Max.I have a prototype circuit working using a SN74AHCT125 (8mA typical recommended o/p current, with 25mA Max continuous).This was all I had to hand for testing, and looking at the data sheet is not really ideal, because if all stepper inputs (En, Dir, Pul) were at 16mA (worse case), this would not be supported the max current the 125 IC.Anyway, my question really is what transceiver (or buffer) IC can I use which has a high enough output current.I did find a single (SOT Package) single channel that fit perfectly, but I cannot remember the details. Most are 8mA or 12mA outputs.Ideally, I would want a 1, 2 , or 4 channel device that can simply take my 3.3V MCU o/p and drive the opto input of the stepper driver at 5V (Max 16mA).I Know I could use a MOSFET (x2 for non inverting) but an IC would be better for me in many respects. (Maybe Multiple BSS138's in a single package would work, but I am looking for a single IC)Any thoughts or ideas about this or better still a part number of a suitable device (Not something like a a 244, but maybe a small footprint single of dual channel device).Thanks

author: Ian.M
author_rank: Super Contributor
timestamp: August 25, 2024, 05:09:36 pm
content: 74LVC1T45 (single) or ...2T45 (dual) bus transceivers. I would expect >24mA with about 0.5V drop @ 5V Vcc on the output side.

author: hobbyelectronics
author_rank: Regular Contributor
timestamp: August 25, 2024, 05:52:44 pm
content: Perfect.That's exactly what I was looking for. Rated at 32mA so plenty of legroom.Not sure why I couldn't find them when I was looking earlier today.Thanks for your reply.

author: langwadt
author_rank: Super Contributor
timestamp: August 25, 2024, 06:11:19 pm
content: you don't need two transistor per output, you can either do common gate/base for non inverting, or you can just use common source/emitter on the low side of the optocouplersif the MCU can handle 5V in open collector mode you can also use that with 5V to the opto and driving with low side open collector directly from the MCU

author: hobbyelectronics
author_rank: Regular Contributor
timestamp: August 26, 2024, 10:49:23 am
content: Hi.I did consider using a transistor setup to control the LED on the opto input of the driver.That's a good idea, but I do like the idea of using the IC to control the conversion from 3.3 to 5V and it gives me the option to swap out the drive for another make/model if required that may have a different input setup.This way as long as its has a 5V i/p it should work.Of course these are all excellent solutions, so thanks again for your replies.Cheers

author: Zero999
author_rank: Super Contributor
timestamp: August 26, 2024, 11:26:30 am
content: Well if the 74AHCT125 works, then it should be fine.Failing that, any 74ACT gate will do.The 74ACT08/74HCT32 come to mind as they're non-inverting AND/OR gates.https://www.onsemi.com/download/data-sheet/pdf/74act08-d.pdfhttps://www.mouser.com/datasheet/2/149/74AC32-180325.pdfIf you need more channels, there's the 74ACT241.https://www.ti.com/lit/ds/symlink/sn54act241.pdf

author: Nominal Animal
author_rank: Super Contributor
timestamp: August 26, 2024, 12:29:04 pm
content: Me only hobbyist, but:I like to keep a dozen or soTI SN74LVC1T45DBV(4.06€ for ten at Mouser) in SOT23-5 in stock, because it can source or sink 24mA, is fast, can do any voltage translation between 1.65V and 5.5V, and most importantly, is large enough for a hobbyist like myself to dead-bug: solder directly to wires and cover with heatshrink, even without a PCB.A suitable adapter PCB is of course very easy to do at e.g. EasyEDA and order from JLCPCB/PCBWay/etc.I've also usedNXP NX138AKs (N-MOSFET) in SOT23-3 for open collector drive; it's very similar to BSS138, but faster (lower gate capacitance). This would require inverting the logic on the host, though. (I got a hundred of thesefrom Mouserfor 5.30€, for logic type use cases, also dead-buggable.) In my experience, these are fast enough for most purposes, and the gate-source voltage can vary between +20V and -20V, which covers all my interfacing needs nicely. They conduct very well at about Vgs=2.5V, so are easy to use with 3.3V logic. I picked them when I first wanted to interface microcontrollers to standard 4-pin 12V PWM fans and tach signals. (25 kHz PWM, two tach pulses per revolution, open collector but with some pull-up requirements/suggestions.)I also keepTI TXU0304in TSSOP-14 in stock for SPI translation (0.79€ apiece at Mouser), and it should work here too (the fourth, return signal, would be unused or free for you to use for other purposes), although its outputs are only rated at 12mA source/sink at 4.5V and higher (absolute maximum is 25mA continuous). For this, you'd need a TSSOP-14 adapter board or your own PCB, though, and I think three SOT23-5 (TI SN74LVC1T45DBVs) would make more sense anyways. The 0.65mm pitch is too dense for me to solder directly wires to, I definitely need a PCB for these.