Help With Design of 48-Channel Constant Current Sink, and Fault Detection

[Andy Chee]

As mentioned in my original post, the load is a Device Under Test (DUT), which is another electronic circuit with critical environmental and functional requirements.

Is the DUT something that already exists as a physical object? Or is it something that you are also designing on paper in conjunction with your test rig?

If it is something you are still designing on paper, then it would be immensely helpful if you could also provide more information on the DUT.

[PCB.Wiz]

2.5 mA on/off.

That's simpler, but you have still not replied to the voltage  compliance ?
Does this need to deliver 2.5mA from 0.5V to 30V, or from 28 to 30V, or ??  - at 2.5mA normal slew rates will limit voltage settling times.

If it needs > 5V..30V, you can open up more options.

Also keep in mind they often skew LED drive outputs deliberately, to reduce bounce effects
eg the OnSemi CAT4016, CAV4016 (would need voltage expansion buffers), mention skews of typ 17ns and max 40ns across each LED and 250ns typ across 16.

You may need to buy-and-try numerous parts, as you are heading into unusual territory.

[Monotoba]

Its bed time here in Montana, but I wanted to chime in and comment. Yes, I don't need to modulate the current. I just need to turn it on and off.

I also wanted to say thank you to everyone commenting as the more ideas I have the better!

Something like a 74HC595 might work. I have read several datasheets on similar devices that include constant current sinks for LEDs, relays, etc. Some of them are stable enough and can get down to 2mA. Most only go down to 5 mA. I only need the current to be anything from 2 to 3 mA, but whatever it is, it cannot change more than +-5%. The system just has to ensure the device has a connection to the jig, must sense open and short conditions, and must turn the current sinks on and off individually, in groups, and all at once.

You all have given wonderful input!

Thanks again!

 

[Monotoba]

Dear Colleagues,

I am reaching out to inquire about an 8051 ROM monitor I programmed into an 80C535 single-board computer (SBC) that I built back in 1992. The EPROM’s window cover is labeled "MONPLUS x 08-09-1992," which corresponds to the date it was programmed.

After rediscovering this SBC while clearing out my late father’s home, I was pleasantly surprised to find it still operational after over 30 years. The system communicates via RS232 at 1200 baud, 8-N-1. However, I am struggling to recall the exact functionality of the monitor commands. So far, I have identified the following:

D: Dumps memory
L: Loads Intel Hex files
I also know that commands I, R, and P perform specific functions, but I am unable to remember what they are.

If anyone has information about this monitor or its command set, I would greatly appreciate your assistance in helping me better understand and use this system.

Thank you in advance for your time and expertise.

Best regards,

Randall Morgan

[Marco]

The 48 window comparators for fault detection are going to dominate the partcount.

[pardo-bsso]

My next thought was an LED driver, Many of them come in 8, 16, 24, and 32 channels, have a fault detection system, and provide constant current. However, Most of them only accept 17 volts max on their outputs. I need 28 min and would prefer 30 volts.

Hi, you can add a common base/gate to each output to raise the voltage without using more expensive chips.