Teensy 3.2 with 12bit Parallel Dac?

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Wow, that's an old part. I'm assuming you mean this, right?

https://www.ti.com/product/DAC811

The good news is it uses TTL level inputs, where anything over 2V is logic high and anything under 0.8V is logic low, so it should be able to receive Teensy's 3.3V signals directly.

There are several ways you could connect this to Teensy. Probably the simplest way would be to just connect all 5 of its control signals to GND and then use 12 pins for the 12 data inputs. I'd probably try that first and get the analog output working before attempting anything more complicated. This chip needs several connections on its analog pins to make the output the way you want... so if you're not experienced with this chip, I'd keep the Teensy side simple while you figure out the analog part.

If you use 12 data signals, you'll probably want to also wire up a 13th signal from Teensy to the LDAC pin. You probably won't get all 12 to change at exactly the same moment. So you'll drive LDAC high to tell the DAC to ignore Teensy's pins, then get the 12 pins set the way you want, then drive LDAR low to tell it to update. That way the output won't momentarily skip to other voltages you didn't want while you set the 12 bits.


Now, a word of warning. This ancient DAC requires 3 power supplies, +5V, +12V, and -12V. Any of these can instantly destroy Teensy if they touch the wrong place, even for just a brief moment. While Teensy 3.2 does have 5V tolerant inputs, that 5V tolerance only applies when the pin is disabled or configured for input mode. The 12 or 13 signals you will connect are all going to be using output mode. If 5V touches any of those signals, you can expect it to destroy your Teensy. Likewise for +12V or -12V - those will completely kill any Teensy if they touch anything other than GND (and might burn the board touching GND depending on how powerful your power supply is). You need to be extremely careful with your wiring. Especially those +12V and -12V wires are a disaster waiting to happen if they're not connected securely or any loose wire is able to accidentally touch them.

Also, if +12V or -12V accidentally touches VIN or VUSB, it could damage your computer by feeding that higher voltage back into your USB port. Be careful.
 
Wow, that's an old part. I'm assuming you mean this, right?

https://www.ti.com/product/DAC811

The good news is it uses TTL level inputs, where anything over 2V is logic high and anything under 0.8V is logic low, so it should be able to receive Teensy's 3.3V signals directly.

There are several ways you could connect this to Teensy. Probably the simplest way would be to just connect all 5 of its control signals to GND and then use 12 pins for the 12 data inputs. I'd probably try that first and get the analog output working before attempting anything more complicated. This chip needs several connections on its analog pins to make the output the way you want... so if you're not experienced with this chip, I'd keep the Teensy side simple while you figure out the analog part.

If you use 12 data signals, you'll probably want to also wire up a 13th signal from Teensy to the LDAC pin. You probably won't get all 12 to change at exactly the same moment. So you'll drive LDAC high to tell the DAC to ignore Teensy's pins, then get the 12 pins set the way you want, then drive LDAR low to tell it to update. That way the output won't momentarily skip to other voltages you didn't want while you set the 12 bits.


Now, a word of warning. This ancient DAC requires 3 power supplies, +5V, +12V, and -12V. Any of these can instantly destroy Teensy if they touch the wrong place, even for just a brief moment. While Teensy 3.2 does have 5V tolerant inputs, that 5V tolerance only applies when the pin is disabled or configured for input mode. The 12 or 13 signals you will connect are all going to be using output mode. If 5V touches any of those signals, you can expect it to destroy your Teensy. Likewise for +12V or -12V - those will completely kill any Teensy if they touch anything other than GND (and might burn the board touching GND depending on how powerful your power supply is). You need to be extremely careful with your wiring. Especially those +12V and -12V wires are a disaster waiting to happen if they're not connected securely or any loose wire is able to accidentally touch them.

Also, if +12V or -12V accidentally touches VIN or VUSB, it could damage your computer by feeding that higher voltage back into your USB port. Be careful.

Hi Paul,

Thank you for the speedy and detailed reply.

Yes, ancient it is! :) I inherited quite a few from my old university LAB with a bunch of other ICs when it shut down recently.

I am going to try out what you suggest and see if I can do them some honor.
Thanks for the warning. I will keep the 12's in check.

Cheers!

RB
 
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