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General => Technical support => Topic started by: Arnulfo Gonzalez on June 09, 2003, 11:32:13 AM

Title: Is there a resistor value limit ?
Post by: Arnulfo Gonzalez on June 09, 2003, 11:32:13 AM

I am planning to read current (transducer output is 0 to +/- 1mA) with ADC input 1. According to ohm?s law i need a 2.5 K resistor to get 5 Volts. Is there a limit on the value of the resistor to connect in parallel with ADC1 ? ???

Title: Re: Is there a resistor value limit ?
Post by: support on June 11, 2003, 07:47:58 PM

If you connect a higher resistor the voltage will become higher (up to the limit of the voltage of the current power supply). However, the ADC input employ series resistors and diode clamp to clamp the input voltage to no more than 0.7V + AVcc. So the maximum voltage that the ADC input will see is about 5.7V. That will drive the ADC to saturation and the value read will be 4092.