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| decent but affordable 16 bit DAC |
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| nemail2:
Hi currently I'm using a MCP4922 in my Lab PSU design. However as I have a gain of 6 currently for my voltage set circuit (DAC goes to opamp, opamp has a gain of 6 and has a darlington in it's feedback loop) and I want to output more than 12.228V (which is VREF = 2048mV * gain of 6) by still being able to control the voltage with 1mV steps, I thought I'd need a higher res DAC. The MCP4922 does have an internal programmable gain of 1 and 2 but with my current setup, at an internal gain of 2 and an external gain of 6 at a VREF of 2048mV I'd be setting my voltage in 6mV steps instead of 1mV. So I found this one: http://www.ti.com/lit/ds/symlink/dac8563t.pdf and was wondering if it was even possible to feed it with 5V (which would give me 5V full scale output) but use 3.3V (that's the MCU's voltage) for the SPI interface. According to the datasheet, the DAC recognizes voltage above 2.1V as logic input HIGH. According to the datasheet it should be possible even without the need of any voltage level shifters. Am I missing something or should this work? Does anybody know better suited/cheaper DACs with 16 bits or even a completely different/better idea how to solve this? Thanks! |
| thm_w:
--- Quote from: nemail2 on June 07, 2019, 11:52:03 pm ---So I found this one: http://www.ti.com/lit/ds/symlink/dac8563t.pdf and was wondering if it was even possible to feed it with 5V (which would give me 5V full scale output) but use 3.3V (that's the MCU's voltage) for the SPI interface. According to the datasheet, the DAC recognizes voltage above 2.1V as logic input HIGH. According to the datasheet it should be possible even without the need of any voltage level shifters. --- End quote --- Yeah looks like you are right, no outputs so no level shifting needed. You may need to do some calibration if the accuracy isn't good enough for you, but the typical values look good. Also depends on your external reference. $8/ea https://www.ti.com/product/DAC8563T There are some DAC8562SDGSR on LCSC for under $5: https://lcsc.com/products/Digital-To-Analog-Converters-DACs_615.html I tried to see what DAC is used in Rigol/Siglent PSU but couldn't find it. |
| mariush:
Have you looked at something like LTC2631H or LTC2640H (12bit, 4.096v internal reference) ... not sure you'd get mV precision, but 2-3 mV should be doable. May seem expensive for a 12bit DAC but if you include the built in reference... or maybe LTC2612 (14bit , needs external reference) |
| MasterT:
MCP4912 has INL +-12 LSB, so basically its' 8-bits DAC and you never get 1mV anyway, even in 0-2.048 range. It's easier /cheaper to use a sigma-delta adc (mcp3421, mcp 3551) and digital pots to lock a loop via micro. Accuracy 18 -3 bits (resistor divider to scale output back) =15-bits or so. If still prefer your design, than look at max5717A - 16 bits, INL +-1 |
| David Hess:
--- Quote from: MasterT on June 08, 2019, 01:55:37 am ---MCP4912 has INL +-12 LSB, so basically its' 8-bits DAC and you never get 1mV anyway, even in 0-2.048 range. --- End quote --- I was going to say this first but you beat me to it. The MCP4922 only has the absolute accuracy of an 8 bit DAC. Higher resolution than accuracy is common in servo applications where the only requirement is monotonic operation. --- Quote ---It's easier /cheaper to use a sigma-delta adc (mcp3421, mcp 3551) and digital pots to lock a loop via micro. Accuracy 18 -3 bits (resistor divider to scale output back) =15-bits or so. If still prefer your design, than look at max5717A - 16 bits, INL +-1 --- End quote --- Or there are 12 bit DACs which have 12 bit accuracy if that is required. |
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