Good cheap 12 bit DAC

[mabd]

Hi;

I am looking for some good cheap DAC serial and parallel
any advice, suggestion
thank you.

[mayler]

There are some PICs with A/D who have 12 bits of precision.

[caveman508]

I use the 18F4423, It has all of the toys and a 12 bit DAC

[maddoc]

I had good results in the past using Microchips TC132x series. TC1322 is a 12-bit DAC using SMBus/I2C. You should be able to buy it for around 2$ (US). Good luck!

Sorry mayler and caveman, but mabd asked for a DAC not ADC.

[caveman508]

Sorry All,

That is what we all get when we don't read, confused and mis-informed.

But I might add, now that I am here:
If you have a PWM module (most are 10 bit though), or create one based on a timer, you get a DAC for free.  The code for the hardware PWM is very easy, the code for any number of bits wide is fairly simple.

Now that is what I call a "Good cheap 12 bit DAC".

Sorry to not have seen DAC, my mind just saw ADC, I have been working with them for a long time.

Caveman

[mabd]

PWM+resistor+cap (Low pass Filter) is not enough for me, I have used it for sometime.


Thanks maddoc, I will look for the datasheet.

Isn't there something "popular"

** caveman508   18F4423:
Mah!!! interesting, I know 16C681/2 (6 or 7 booh!!!)
and I think 16F785

But 18F with DAC; interesting

[caveman508]

mabd,

As maddoc pointed out, I read your request wrong, I have never seen a PIC with a built in DAC.

PWM+resistor+cap (Low pass Filter) is not enough for me, I have used it for sometime.

Why is that simple approach not "enough" for you?

Caveman

[maddoc]

Mabd, here is the datasheet: http://www.ortodoxism.ro/datasheets/microchip/21388b.pdf
Those parts are simple, robust DACs. I always used them without problems.

Caveman, if for example one wants 100k samples /second then PWM simply won't cut it, you must set the PWM for at least 4 times the sample frequency (8 times is even better) so you won't have hiss in the signal. No PIC can produce such a high frequency PWM at more than 4bits precision. This is a clear case for DAC's.

Let's assume you want to output a 16kHz wave file. You must put the PWM for 4x that frequency to still have 8 bits precision, but you will still have a high pitch hiss and if you filter that out than you loose the upper freq. part of that wave file. If you try 8 or 10 times that frequency you won't get 8bits precision anymore. Now just think of a 96kHz wave file...

On the other hand if you use a 8bit DAC then all your problems are solved and you just have to pump those 8bits at the required frequency to get a clear and crisp sound.

(a pic 18F with a built in DAC would be great! somebody should hear this at microchip - how hard would it be to put an 8 or even 16bit register and 16 or 32 100k and 200k resistors in there, tied to a pin?)

[adrian]

There are several ways to construct a DAC. The PWM RC circuit is only suitable for low frequency application. typically 0-100Hz.
Hopefully you have a lot of extra pins. R2R Ladder is quite easy to construct but it used up lots of your i/o pins. It has good accuracy and the cheapest that i can think off without using extra external part. Use 12pins instead of 8pins.Resistors value should be changed. Buffer the output (opamp/transistor) incase drive current is too low. Hope this helps.

More detail information here;
DA Conversion Using PWM and R-2R Ladders to Generate Sine and DTMF Waveforms
http://ww1.microchip.com/downloads/en/AppNotes/00655a.pdf

[jestanoff]

Look for DAC7512 from Texas Instruments. It is very cheap and fast serial 12-bits DAC.
http://www.ti.com/lit/gpn/dac7512

[mabd]

thank you everybody, you are very nice.
a small gift to everybody
Read about
The Man Behind the Microchip: Robert Noyce and the Invention of Silicon Valley
http://www.sonsivri.com/forum/index.php?topic=11586.0

[mayler]

Sorry for my mistake... I read ADC   

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1155,C1005,P1509

I think it maybe can attend your necessity.
There are cheaper models, but with other caractheristics...