When choosing the input voltage range,
the input common mode voltage range (VICR) must be taken in to account.
If operating temperature is above or below 25°C the VICR can range from 0
V to VCC– 0.7 V. This limits the input voltage range to as high as
VCC– 0.7 V and as low as 0 V. Operation outside of this range can
yield incorrect comparisons.
Below is a possible list of input
voltage situation and their outcomes:
- When both IN- and IN+ are
both within the common mode range:
- If IN- is higher than
IN+ and the offset voltage, the output is low and the output
transistor is sinking current
- If IN- is lower than
IN+ and the offset voltage, the output is high impedance and the
output transistor is not conducting
- When IN- is higher than
common mode and IN+ is within common mode, the output is low and the output
transistor is sinking current
- When IN+ is higher than
common mode and IN- is within common mode, the output is high impedance and
the output transistor is not conducting
- When IN- and IN+ are both
higher than common mode, the output is low and the output transistor is
sinking current