DAC With built-in up/down counter

[lucidtech]

Hi All,

It's my first post here, so please be kind

I have been out of the electronics design area for around 10 years and now I'm just getting back in for a small project.

As the title suggests, I'm looking for a DAC device with a built-in up/down counter. This is for a project to effectively generate ramp type waveforms from 0-12V. Ramp up to 12V and hold for a period of time then ramp down. Similar to a fade-in fade-out.

I can do this with a DAC8080 with an 8 bit up/down counter, this is no problem, I'm looking for a device that does this in one package. I'd assume it would only be an 8 pin package (maybe 14 pin)

Any thoughts/suggestions would be greatly appreciated.

Kind Regards,
Robbie...

 

[Mikebits]

A DAC converts a digital signal to a analog signal, a counter updates based on logic pulses, your digital input to the DAC would determine the waveform generated.

 

[crutschow]

You will not likely find a DAC with a build-in counter. You will need to use an external one.

 

[ronsimpson]

0 to 12V from a DAC. Probably not.
0 to 5V + amplifier. Yes

8 bit? 10 bit? 6 bit?
How fast?

How about three 8pin ICs?

 

[lucidtech]

Possibly, but I'm still looking (and hoping) Thanks for the reply

 

[lucidtech]

Yes I probably will need an external amp and speed is not an issue as it will be slow, approx. 1hz.

 

[ronsimpson]

Option A.
1.) 6 pin IC: amplifier with 0 to 12V out.
2.) 6 pin Micro controller with software PWM.
Option B.
1.) 6 pin IC: amplifier with 0 to 12V out.
2.) 8 pin DAC.
3.) 6-8 pin Micro controller.

I know you don't want to program a micro but I just don't see other choices.
Could easy fit with in 1cm x 1cm.

 

[MrAl]

Hi,

Depending on how much accuracy you need and bits of resolution, you might find a digital potentiometer with up/down count inputs. You might be able to use that as a variable voltage divider. You'd have to look for the parts as it's been a while since i looked them up myself and dont have the part numbers anymore.

 

[ronsimpson]

digital potentiometer with up/down count inputs. You might be able to use that as a variable voltage divider.

There are a number of "digital pots" that have UP and DOWN inputs.
Data sheet attached.

 

[ronsimpson]

Digital pots have high output impedance and need a buffer.

The PIC12F1501 is a 8 pin micro with a 5 bit DAC that is of the type of a digital pot. Needs a buffer/amplifier. It is a counter and DAC in a 8 pin package.

 

[ronsimpson]

The PIC12F1822 and PIC16F1823 have 8 or 10 bit PWM DACs and a 5 bit DAC. Everything but the amplifier in 8 pins.

 

[ericgibbs]

hi,
These older A2D2A IC's have a 8 bit internal counter.

 

[ronsimpson]

Eric, Good find. I have not thought about these parts for years. They make a good ramp wave, sawtooth. Won't count down. Can anyone find a part.

 

[lucidtech]

Hi All,

Just a quick note to say thank you everyone for all your efforts. These are all great suggestions and I know your time is limited and valuable and I really appreciate it.

I do like the idea of using a digital pot, so I might look into that option and see where that takes me.

In the meantime, if anyone has any further input, again it will be greatly appreciated.

Robbie...

 

[lucidtech]

Hi All,

Once again thanks for all your responses.

Just thought I'd drop a note to say I've decided on the device. The AD5220. It's exactly what I was hoping for. I've ordered a few (AU$2.50 each, cheap enough) and will be playing this weekend.

Robbie...

 

[MrAl]

Hi,

Did you get the 10k type?

 

[lucidtech]

Hi,

Did you get the 10k type?

Yes I did.

 

[lucidtech]

Hi Again,

Hope everyone is well...

I have the AD5220 and it works well, just like I need it to. I'd like to use a N Channel Enhanced MOSFET to switch the load (LED Strips connected to the Drain), but I have only tinkered with Logic Level MOSFETs, which aren't good for ramping up and down in a linear way.

Can anyone suggest a suitable device? Also, as I understand it, in order to switch these MOSFETs on hard, the Gate voltage needs to go higher than the Drain voltage, is this correct? If so, what do I use to achieve this?

Thanks in advance.
Robbie...