DACs on microcontrollers

Lord Steve

One can easily find microcontrollers with ADCs on them.· However, I can't find any well-known microcontrollers which have a DAC output.· It would be really sweet for audio apps to have both an internal ADC and an internal·DAC.· Am I missing something here?· I am not an electronics expert so maybe good-quality external DAC-ing is way easier than I know.

Thanks!

Paul Baker

Typically analog voltages are generated using PWM on a resistor-capacitor low pass filter connected to a pin, if the load has a low resistance the voltage will need to be buffered using an op amp configured as a voltage follower.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

N0QBH

Most PIC micros with built in comparator modules also have a 4 bit DAC used as a voltage reference. On many of the chips, this reference (VRCON) is available on one of the pins. If 4 bit resolution is enough for your application, it can be a simple solution. Usually, it's a good idea to buffer the signal with a op amp configured as a unity gain voltage follower unless the circuit is high impedance.

Lord Steve

Thank you for your responses.··Does a DAC take up to much room on silicon?· I'm just wondering why you don't find a plain ol' DAC output on micros (like PICs).

Thanks!

LoopyByteloose

I suspect the reasoning behind excluding DACs as a microcontroller feature is two fold.
1. One can easily use PWM or serveral other methods to produce an analog signal. Even Sigma-Delta can do it.
2. Usually the analog signal requires additional amplification to be of some use. These choices may be too diverse for the chip makers to care to develop inventory.

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