Contents
- 1 How to protect ADC inputs from overvoltage?
- 2 How does the series resistor protect the ADC?
- 3 Can a strong driver circuit damage an ADC?
- 4 Are there protection diodes between the reference and the ground?
- 5 When does overdrive of ADC inputs take place?
- 6 How is series Your used to protect ADC inputs?
- 7 Why are ADC conversions inaccurate in a multi-ADC system?
- 8 Which is the minimum and maximum ADC range?
- 9 How does the ads1115 16-bit ADC work?
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.
How to read battery voltage with STM32 ADC?
Remember, if you have two resistors (R1 and R2) in series with a total voltage of V across them, the voltage across R1 is: Simple voltage divider to cut the battery voltage in half for the ADC.
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.
How are Schottky diodes connected to the ground?
The Schottky diodes are connected to the ground and a 5 V system rail capable of sinking current. Without the Schottky diodes, there is a reference disturbance when the input exceeds the reference and ground by a diode drop. As can be seen, the reference disturbance is completely removed with the Schottky diodes.
When does overdrive of ADC inputs take place?
Overdrive of ADC inputs generally occurs when the rails of the driving amplifier are significantly greater than the max input range of the ADC—for example, if the amplifier runs from ±15 V and the ADC input is 0 V to 5 V.
How is series Your used to protect ADC inputs?
The series R in the RC filter between the amplifier and the ADC input can also be used to limit the current seen at the ADC input during an overvoltage condition. However, this will be a trade-off between current limiting and ADC performance. Larger series R will give better input protection but result in greater distortion in the ADC performance.
How does an input clipping diode protect the input?
Figure 13: Reading high voltage inputs. The input clipping diode to ground is to protect from less than zero volt spikes. The input clipping diode to the positive bus is removed in favor of the zener diode after the current limiting resistor. This provides a known voltage for the input pin and reduces the amount of current shunted to the power bus.
Why are ADC conversions inaccurate in a multi-ADC system?
In a simultaneous sampling multi-ADC system sharing the one reference, the conversions on the other ADCs will be inaccurate, as the system depends on a highly accurate reference voltage. Subsequent conversions may also be inaccurate if the recovery time from the fault condition is long.
Which is the minimum and maximum ADC range?
The ADC range is the maximum and minimum ADC input (e.g., 0 to +3.3V). The ADC resolution is the smallest distinguishable change in input (e.g., 3.3V/4095, which is about 0.81 mV). The resolution is the change in input that causes the digital output to change by 1. Range (volts) = Precision (alternatives) • Resolution (volts)
How is the ADC used in an embedded system?
An embedded system uses the ADC to collect information about the external world (data acquisition system.) The input signal is usually an analog voltage, and the output is a binary number. The ADC precision is the number of distinguishable ADC inputs (e.g., 4096 alternatives, 12 bits).
How does the ads1115 16-bit ADC work?
Normally you would need two inputs to switch between 4 addresses but the ADS1115 16-bit ADC uses a clever scheme. The single address input is sampled continuously and if you connect it to GND, VDD, SDA or SCL you can set the address from 0x48, 0x49, 0x4a, 0x4b respectively.