blakeAlbion
Well-known member
Seems the 16 bit dac has become rare? I’m looking for some kind of breakout like a pmod board. I need a real dac that gives me a voltage for a number, not a stereo audio stream.
Where can I obtain a 16 bit dac to generate control voltage?
- Thread starter blakeAlbion
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Nominal Animal
Well-known member
They're rare, because their uses are limited (compared to say ADCs, that can be used to measure a number of things); and it is almost as easy and cheap to design a bespoke one using the rapid prototyping services like JLCPCB and PCBWAY and others that are nowadays so easily available.
For example, I have a Teensy-based display project, where I wanted a LED backlight to be absolutely flicker-free, individually adjustable (so I can get uniform backlight distribution), and also dimmable (for very smooth power on and off). With some help from experts at the EEVblog Beginners forum, they helped me design a suitable circuit (including a bit of temperature compensation) using just a few transistors, resistors, and an MCP4801 SPI DAC (for the dimming control via MCU). I simulated the entire thing using ngspice (in Linux in Qucs-S), and learned a lot about practical circuit design in the process. My actual circuit will have both the DAC and a physical potentiometer for controlling the maximum brightness, so the DAC only controls the ramping between that and no backlighting at all. This particular DAC has an internal voltage reference that matches well to my needs (it can output 0-2.048 V or 0-4.096 V, although the latter requires operating voltage over 4.1 V), with sufficient stability for my needs, and the 8-bit resolution suffices for this use case. So, I only need a couple of bypass capacitors, and that's it.
Since I recently took a look at both I2C and SPI DACs (I got mine off Mouser), I can say that the DAC price itself rises dramatically when the bit depth increases. The 8-bit ones are cheap (I paid 1.5€ for mine), and the 16-bit ones start at 8€ to 9€ apiece (aside from DAC161P997, which is designed for 4-20mA current loops), but moreover, many of them require an external voltage reference. There are a few (Maxim MAX5136, Texas Instruments DAC8562, Analog Devices AD5660) that do have internal references that give them output voltage ranges of 0 to 2.44 or 2.5 or 5 V.
Thus, for anyone to help you further, perhaps you could state what kind of output voltage range (and at what kind of current) do you need? What kind of sample rate, i.e. how many voltage changes per second? And what kind of interface –– I2C, SPI, something else –– would you prefer?
For example, I have a Teensy-based display project, where I wanted a LED backlight to be absolutely flicker-free, individually adjustable (so I can get uniform backlight distribution), and also dimmable (for very smooth power on and off). With some help from experts at the EEVblog Beginners forum, they helped me design a suitable circuit (including a bit of temperature compensation) using just a few transistors, resistors, and an MCP4801 SPI DAC (for the dimming control via MCU). I simulated the entire thing using ngspice (in Linux in Qucs-S), and learned a lot about practical circuit design in the process. My actual circuit will have both the DAC and a physical potentiometer for controlling the maximum brightness, so the DAC only controls the ramping between that and no backlighting at all. This particular DAC has an internal voltage reference that matches well to my needs (it can output 0-2.048 V or 0-4.096 V, although the latter requires operating voltage over 4.1 V), with sufficient stability for my needs, and the 8-bit resolution suffices for this use case. So, I only need a couple of bypass capacitors, and that's it.
Since I recently took a look at both I2C and SPI DACs (I got mine off Mouser), I can say that the DAC price itself rises dramatically when the bit depth increases. The 8-bit ones are cheap (I paid 1.5€ for mine), and the 16-bit ones start at 8€ to 9€ apiece (aside from DAC161P997, which is designed for 4-20mA current loops), but moreover, many of them require an external voltage reference. There are a few (Maxim MAX5136, Texas Instruments DAC8562, Analog Devices AD5660) that do have internal references that give them output voltage ranges of 0 to 2.44 or 2.5 or 5 V.
Thus, for anyone to help you further, perhaps you could state what kind of output voltage range (and at what kind of current) do you need? What kind of sample rate, i.e. how many voltage changes per second? And what kind of interface –– I2C, SPI, something else –– would you prefer?
blakeAlbion
Well-known member
Thanks Nominal!
That validates my question.
Ben
That validates my question.
Ben
PaulStoffregen
Well-known member
Just went to look at what Ornament & Crime used. As I recall, they put a lot of work into finding the best DAC to use for synth CV controlling oscillator pitch. Sure enough it's the same DAC8562 part just mentioned.
Digikey has them in stock at $18 single, $13 at hundreds. Looks like questionable Chinese merchants sell it at about $12 to $15.
Digikey has them in stock at $18 single, $13 at hundreds. Looks like questionable Chinese merchants sell it at about $12 to $15.
blakeAlbion
Well-known member
I have a couple 12 bit dacs with an SPI interface. This was Ages ago. I was able to get a sketch working with the Teensy. These are the Digilent PMOD DA4 boards using the AD5628. 8 channels, so I was saving them for the day I was going to make an analog synth. Maybe I should dust them off.