LTC1864 Help

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#1
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I'm looking for an ADC to sample an audio input and have a few questions.

First off, I have purchased a LTC1864, it will be used to sample line level audio (2 channel) but I'm not sure if the ADC I purchased will actually work with two channels. This is the ebay listing that I bought it off:
http://www.ebay.com/itm/27113550...

And this is the datasheet:
http://cds.linear.com/docs/en/da...

The datasheet specifies that the LTC1864 MSOP8 has two inputs, an in+ and in- which leads me to believe that this particular device is a differential converter. Meaning the output will be the difference between the two inputs. But there is an analogue reference pin... which confuses me further.

But the ebay listing says "LTC1864CMS8 ~ LTC1864 μPower, 16-Bit, 250ksps 1- and 2-Channel ADCs in MSOP IC"

Is there some sort of tricky way to make a differential converter into a 2-channel converter? Or is the ebay add just incorrect?

Lastly, since I'm sampling line level audio, my input is going to go negative with respect to ground. What is the best way to sample a negative voltage, I was thinking of just adding a DC bias with a passive adder. I know the best way would be to add the bias with an active adder (op amp circuit) but unfortunately I have a single supply (+5v).

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From the data sheet it's clear that the LTC1864 is a single channel converter with differential inputs and the LTC1865 is a dual channel, single ended inputs. Both need 0-5V in and no negative signals.

It pays looking at the datasheet BEFORE a purchase. :-)

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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So no, I can't pull some trick to make a differential converter able to convert two channels and the ebay add was just wrong?

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Well semiwrong I guess. :-) It does say 1 channel as well as 2 channels but the 2 channels is not the advertised one.

See http://www.ebay.com/itm/LTC1865A...

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Why did you not get a device specifically for audio?

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Kartman wrote:
Why did you not get a device specifically for audio?

I didn't know where to look, could you point me in the right direction?

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You use the device selection guide at the semiconductor manufacturer's site. Texas Instruments, Analog Devices, Linear technologies.

Imagecraft compiler user

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Hey guys if I could get a little help that would be awesome. I have spent a couple hours on it already and maybe you guys might think of a device off the top of your heads :P Its worth a shot.

So it needs to be:
- 2 channel
- Audio (48ksps+)
- +5v(analog and digital)
- SPI protocol
- <$10
- 16bit to 24bit

Then I need a matching DAC with close to the same specs. I have looked at a lot of Data conversion units and most of them seem to use I2S, which I can't interface with my ATMEGA32.

Any help would be much appreciated.

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Take those terms you typed in, and find the check box in the product selector at the TI, AD and LT sites that has the same words. The xmega and avr32 are designed for audio. avr32 might have an i2s chennel or two on it.

Imagecraft compiler user