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TL331 Hysteresis

Other Parts Discussed in Thread: TL331, TLV3501, TIPD144

The TL331 datasheet does not discuss the inherent hysteresis of this comparator.  As a comparative (excuse the pun) example, the TLV3501 has an extensive description of hysteresis, along with a calculation of the affect when a feedback resisotr is added from OUT to IN+:

. . . comparator inputs have little noise immunity within the range of specified offset voltage (±5mV). For slow moving or noisy input signals, the comparator output may display multiple switching as input signals move through the switching threshold. In such applications, the 6mV of internal hysteresis of the TLV350xmight not be sufficient. In cases where greater noise immunity is desired, external hysteresis may be added by connecting a small amount of feedback to the positive input. Figure 2 shows a typical topology used to introduce 25mV of additional hysteresis, for a total of 31mV hysteresis when operating from a single 5V supply. Total hysteresis is approximated by Equation 1:

VHYST _

( V_)_R1

R1_R2

_6mV

I would like to see the same information for the TL331, as I have a 604k resistor added in a similar manner ( out to IN+, along with a resistor dvider from 12v 22.1k and 17.4k to 0v, 1%) at the IN+ pin.

~Leonard