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ADS1113: 16 Bit ADC (and DAC) suitable for Bench Power Supply - Low Cost is Important

Ted Mawson 3.0
Expert 1795 points
Part Number: ADS1113
Other Parts Discussed in Thread: ADS1118, ADS1115

I'm coming up with a design for a bench PSU that will have 3 isolated outputs; each output will have a small slave microcontroller 'talking' over a digital isolator using I2C/SPI to a master micro that runs the display, buttons etc.  The PSU will have a max output of 32V at 6A so 16 bits will get me <1mV resolution which I want.  Sampling a few hundred times per second is fine but ideally, I want to use the same ADC to sample voltage and current by switching th einput in some way plus I'll need a 16 bit DAC to set the desired voltage from the slave microcontoller(s).  Size and power consumption isn't very important but cost is.  The ADS1113 is small (making it difficult to prototype) but it might do the job but I wonder if there are ICs that have ADC and DAC on the same chip? There are many Audio devices that are 16 bit ADC + DAC that 'talk' I2S but this would be a pain to implement I think.

Any suggestions for TI devices that would be suitable for my requirements?

  • 0
    TI__Guru* 97465 points

    Ted,


    First, I don't know of any combined ADC+DAC type parts that could be used for your application.

    Similar to the ADS1113, I think the ADS1115 would be close to what you would like to use for your system ADC. This would be an ADS1113 with an configurable input multiplexer and a PGA with some gain to measure different full scale ranges. I would note that the maximum data rate is 860SPS so if you want to run the ADC a several hundred samples per second, you might be pushing it. Again these devices have multiplexers, so you'd be taking data sequentially, so you'd need to cycle through the different measurements. Additionally, you'd be setting the configurations with I2C, which might be a bit slow to make multiple measurements with multiple devices. The communication with the ADS1118 may be a bit faster (this is similar to the ADS1115, but with SPI communication).

    I'd also point out that the input voltage of the ADC is limited to the input range of the device. This means that the ADC can only measure voltages from VDD to GND. If you plan on measuring the PSU supply voltages (up to 32V), then you'll need some sort of voltage divider to get the input low enough. Additionally, if you want to measure the PSU current, you may need to do it with a low side current sense measurement, if you're making a direct measurement with a current sense resistor.

    As for the DAC, I would post another question asking about DAC product possibilities and you can reference this post. As I mentioned, I don't know of any ADC+DAC combo devices. However, they can can help you with a product selection.


    Joseph Wu

  • 0 in reply to Joseph Wu
    Expert 1795 points

    Great answer, thanks Joseph.

    Ted