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How to protect ADC from overvoltage?
A way of eliminating overvoltage issues completely is to use a single-supply rail for the amplifier. This means the driving amplifier can never swing below ground or above the max input voltage if the same supply level is used as for the reference voltage (max input voltage), which is 5 V in this example.
How to protect ADC?
To protect the input of the ADC, the TVS diode breakdown voltage should never be lower than the absolute maximum ratings for the ADC. For example, if the absolute maximum rating of the ADC is plus/minus 15 volts, the breakdown voltage should be a lower voltage, such as plus/minus 12 volts.
Can ADC take negative voltage?
If you tie one channel to ground (called pseudo-differential mode), the ADC can accept a negative input voltage on the other, and translate it into a negative number, all without needing a negative voltage.
How do diodes work with negative voltage?
If the voltage across a diode is negative, no current can flow*, and the ideal diode looks like an open circuit. In such a situation, the diode is said to be off or reverse biased. As long as the voltage across the diode isn’t negative, it’ll “turn on” and conduct current.
How to protect ADC inputs from overvoltage?
A common issue that arises when designing an ADC circuit is how to protect the ADC inputs from overvoltage. The protection of ADC inputs has many scenarios and potential solutions. ADCs from all vendors have similar needs in this respect.
How does the series resistor protect the ADC?
The series resistor after the Schottky diodes also helps limit the current into the ADC if the internal diodes turn on slightly. For extra protection, if the reference has little to no sink current capability, a Zener diode or clamp circuit could be used on the reference node to guarantee the reference voltage cannot be pulled too high.
Can a strong driver circuit damage an ADC?
If the REF node is not driven by a strong driver circuit, then the voltage at the REF node (and input) will rise above the absolute maximum rated voltage and the ADC may be damaged if the voltage exceeds the breakdown voltage of devices on that process.
Are there protection diodes between the reference and the ground?
This circuit is representative of what we see in the AD798x (for example, the AD7980) family of PulSAR ® ADCs. There are protection diodes between the input, the reference, and the ground. These diodes are capable of handling high currents of up to 130 mA, but only for a few milliseconds— not for longer periods or repeated overvoltage.