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Old 8th February 2008, 02:35 PM   #1
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Default Digital pot resistance measurement

I am using the PGA2320 from TI as a volume control/preamp. I want to measure the effective resistance of the digital pot to make sure my microcontroller is in fact increasing/decreasing the resistance levels properly at the touch of the attached volume buttons.

On the analog side, if I have nothing connected to the analog pots besides the analog ground, will I still be able to measure the resistance from wiper to ground with a simple voltmeter? I wonder if it will work like a conventional pot, because the digital potentiometer elements are actually a bunch of FETs in a ladder configuration.
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Old 8th February 2008, 06:10 PM   #2
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Default Re: Digital pot resistance measurement

Quote:
Originally posted by rtarbell
I am using the PGA2320 from TI as a volume control/preamp. I want to measure the effective resistance of the digital pot to make sure my microcontroller is in fact increasing/decreasing the resistance levels properly at the touch of the attached volume buttons.

On the analog side, if I have nothing connected to the analog pots besides the analog ground, will I still be able to measure the resistance from wiper to ground with a simple voltmeter? I wonder if it will work like a conventional pot, because the digital potentiometer elements are actually a bunch of FETs in a ladder configuration.
This chip isn't just a digital pot. If you look in the datasheet, you'll see that the output is buffered with an opamp. Also, there are two independent digital pots, one as an attenuator on the input, and one as a gain selector in the opamp feedback loop. This chip is also capable of producing gain, so it can't be modeled as a variable resistor. You won't be able to measure the variable resistance of the internal components.

DS1802 etc. are less complex parts that are just pots.
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