High-speed 24V - 5V logic level converter

Official Hardware Pro Solutions Portenta Machine Control
1

Hello everyone!
This is my first post, so please bear with me. I need some help finding a suitable high-speed 24V - 5V logic level converter.

Project
I am planning to use an Arduino Portenta Machine Control to coordinate several motors and sensors for a research imaging setup. I have several different sensors (mass spectrometer, proximity sensors, position encoders, etc) which all capture data at different frequencies, so synchronising them to work together is a bit of a challenge! Specifically, I have some Thorlabs KDC101 brushed servo motor controllers which can execute preprogrammed motor moves when they receive a 5 V TTL "trigger", or can output a 5 V TTL "trigger" when specific motor positions are met. I also have several switches which can be turned on / off using a 5 V TTL trigger.

Aim
I need the Portenta to execute a function (such as take a measurement) when it receives a 5 V trigger. Also, I need the Portenta to be able to output 5 V triggers to control external equipment (such as turning on a switch).

The problem
The Portenta Machine Control board uses 24 V logic. I therefore need a logic level converter to input and output 5 V triggers. High-speed switching is very important for this application, so the logic level converter needs to be as fast as possible (ideally < 1 microsecond delay).

Why not try a 5 V native board
The Arduino technical support team have recommended that I use the Portenta board for high-speed applications. "Maker" series Arduino boards would be too slow.

Isolation would be nice
Some of our equipment is quite sensitive. For example, the Thorlabs KDC101 will break if we accidentally put more than 5.25 V across its trigger input. To protect equipment, it might be good to have some isolation. I came across optocouplers, which physically isolate the two sides (24 V never actually connected to the 5 V) and then use light to cross the gap. I'm not sure if optocouplers are the only way to get isolation, or whether the other logic level converter designs also have clever built-in protections?

Summary of design requirements

  1. 24 V - 5 V logic level conversion
  2. As fast as possible (< 1 microsecond delay)
  3. Protection between the two sides
  4. Total of 10 channels (it would be great if these were all together on the same board, but it's not essential)

What solution would you recommend?

Thank you for your help :smiley:

2

Get a scope and find out which solutions do (not) match your requirements. Then try to tune the slow solutions.

What's more important, propagation delay or slope symmetry?

3

24 V - 5 V logic level conversion, I would use a resistor divider unless the grounds cannot be shared. I would use the divider then feed that output via 100k resistor into a buffer such as a 74C914 running at the processor voltage. This gave me reasonable speed and survived nasty transients form the power system.

Opto is good for complete isolation, here is a link where you can make a choice of what you want. Optocoupler High Performance Transistors

You can put as many as you like on one board, I have seen as many as 16 available on commercial equipment. I have not used this but here is an image of one.
image

4

Thanks for the suggestion. Could you clarify what you mean by "slope symmetry"? My background is clinical, not in electrical engineering, so there's a lot of confusing new terminology to learn!

5

Turn ON time delay may be different from turn OFF time. This can lead to wrong PWM duty cycle or loss of short pulses.