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Cheaper & Better ADCs Are Here

Every time I turn around, it seems like there is another ADC on the market that has improved upon the specs of the parts that came out last week. Not too long ago, if you wanted more than 8 bits of data at more than 100kSa/s, you would pay dearly for it. Now, these devices are like jelly beans.

You can get a 12-bit device that zooms along at 187.5kSa/s conversion rate from Touchstone Semiconductor. The TS7001 would be perfect for industrial applications. Typical usage is in process control equipment, where lots of sensors are monitored (temperature, pressure, flow rate, voltage, current) and some sort of control is effected (motors turned on and speed adjusted, linear or rotary actuators powered on, valves opened and closed). For some sensor inputs, you really don't need a very fast ADC (e.g., temperature). But for motor control, you do.

At first glance, you might not think so — the motor (probably an AC induction motor) is powered from 60Hz, right? Maybe not. More likely, it's driven from a variable voltage, variable frequency power inverter. The inverter synthesizes the necessary voltage and frequency from a PWM waveform to get the motor to turn at the correct speed without overheating. It is preferable to monitor the current and voltage output of the inverter at a sufficiently high rate to prevent damage to the inverter or motor. For this reason, a data conversion rate above 100kSa/s is highly preferred.

These devices from Touchstone are low cost enough (the '7001 is $1.15 in 1,000 piece quantities) that even if you don't think you need the speed, you might as well go for it. Part of the reason they are inexpensive is they are packaged in an eight-pin MSOP. Packaging costs are a significant portion of IC cost. Of course, since it's only an eight-pin package, you know its data output is in serial format.

Besides industrial applications, the device could even be used in portable equipment, where battery life becomes an issue. The device consumes 3mW when converting at full speed (supply voltage: 2.7V to 3.6V); it draws 1μA when in shutdown mode. It has an internal voltage reference with initial accuracy of ±0.5% and a tempco of 30ppm/°C. Its integral nonlinearity (INL) is spec'd at ±1LSB. Operating temperature range is industrial (-40°C to +85°C).

Oh, and incidentally, it's a dual ADC, so you are actually getting two in one eight-pin package. I need to take a closer look at these to see if they would be suitable for audio applications. If the noise is low enough, they might even lend themselves to one of my guitar-effects projects.

4 comments on “Cheaper & Better ADCs Are Here

  1. Michael Dunn
    February 15, 2013

    We're in a golden age for converters, that's for sure. See an old ADC here: Remembrance of Chips Past.

    Guess this chip would be usable for lower quality audio. Oversample and get maybe 14 bits out of it.

  2. David Maciel Silva
    February 15, 2013

    Maybe for a specific application of audio amplifier, it is interesting to use an integrated circuit that enables a good output power:

    http://www.digikey.com/product-detail/en/TDA2004R/497-11748-5-ND/2035169

    The cost is a little higher, but perfomace output and relatively good.

    Thinking of a digital analog converter, I found that this model of IT, in a resolution of 24 bits.

    http://www.ti.com/lit/ds/symlink/ads1225.pdf

  3. jkvasan
    February 18, 2013

     

    In our products, during the 90's, the first ever and extensively used IC was the ICL7107 from Intersil. Then came the ICL7135. Though these were pocket-friendly, they were not fast enough as they used Dual Slope Method.

    MCP3202 from Microchip became the next choice as it was the only 12 bit ADC avaialble at that cost. 

    Touchstone ADC seems to be very promising – functionality with good price. Shall try in one of the designs soon.

  4. Brad Albing
    February 18, 2013

    I used those Intersil parts back around 1978-1980 – worked for a small company (Hickok) manufacturing  a variety of test equipment models. We used the '7106 and '07 in a nice DMM we made. Good parts for that application, but like you said, pretty slow.

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