neiltechspec
Senior Member
As subject - What's an M2 chips ADC input impedance ?
Does anybody have a quick answer.
Neil
Does anybody have a quick answer.
Neil
What's an M2 chips ADC input impedance ?
- Thread starter neiltechspec
- Start date
Hi,
The base PIC data sheet recommends a source resistance of less than 10 kohms, which suggests an input impedance of >10 Mohms for 10-bit accuracy.
The input resistance is not defined but it's basically "very high". However, the input load is principally a capacitance which is briefly connected to the input (to "sample and hold" the voltage). Thus, you can use a higher than 10 kohms source resistance by connecting a capacitor (say 10 - 100 nF) from the analogue input to ground.
Cheers, Alan.
The base PIC data sheet recommends a source resistance of less than 10 kohms, which suggests an input impedance of >10 Mohms for 10-bit accuracy.
The input resistance is not defined but it's basically "very high". However, the input load is principally a capacitance which is briefly connected to the input (to "sample and hold" the voltage). Thus, you can use a higher than 10 kohms source resistance by connecting a capacitor (say 10 - 100 nF) from the analogue input to ground.
Cheers, Alan.
neiltechspec
Senior Member
Problem is, the O/P impedance of what I want to connect is 85k, it will have a 1uF cap on the O/P (LTC1966 RMS to DC converter).
I may have to buffer it then, although I might have to anyway to increase conversion O/P voltage.
Neil
I may have to buffer it then, although I might have to anyway to increase conversion O/P voltage.
Neil
Hi,
It depends what resolution you require (full 10 bits? ) and the maximum temperature that might be encountered. But I would think that in most cases an 85k source impedance should be "good enough", particularly if the source capacitance is not a "leaky" electrolytic type.
You may be able to increase the "sensitivity" a little by using the FVR as the Reference, (or other methods are possible).
Cheers, Alan.
It depends what resolution you require (full 10 bits? ) and the maximum temperature that might be encountered. But I would think that in most cases an 85k source impedance should be "good enough", particularly if the source capacitance is not a "leaky" electrolytic type.
You may be able to increase the "sensitivity" a little by using the FVR as the Reference, (or other methods are possible).
Cheers, Alan.
neiltechspec
Senior Member
Won't be a leaky electrolytic, LTC1966 datasheet recommends Metalized Polyester Film.
Neil.
Neil.