ADCMP354YKSZ-REEL7 Datasheet, PDF (9/12 Pages) Analog Devices – Comparators and Reference Circuits

APPLICATIONS INFORMATION
ADDING HYSTERESIS
To prevent oscillations at the output caused by noise or slowly
moving signals passing the switching threshold, positive feedback
can be used to add hysteresis to the noninverting parts
(ADCMP354 and ADCMP356).
For the noninverting configuration shown in Figure 20, two
resistors are used to create different switching thresholds,
depending on whether the input signal is increasing or decreasing
in magnitude. When the input voltage is increasing, the threshold is
above V_REF, and when it is decreasing, the threshold is below V_REF.
The upper input threshold level is given by
( ) _{VIN_HI =}
V_REF
R1 + R2 + R_PULLUP
R2 + R_PULLUP
− V_CCR1
where V_REF = 0.6 V, assuming R_LOAD >> R2, R_PULLUP
The lower input threshold level is given by
V_{IN_LO}
=
V_REF (R1+ R2)
R2
The hysteresis is the difference between these voltage levels and
is given by
∆V_IN
=
V_CC R1
R2 + R_PULLUP
V_CC = 5V
V_IN
R1
ADCMP354
V_REF = 0.6V
R_PULLUP
OUT
R_LOAD
ADCMP350/ADCMP354/ADCMP356
VOLTAGE DETECTOR
The ADCMP350/ADCMP354/ADCMP356 can be used to
monitor voltages, such as battery monitoring or threshold
detectors. Using a resistor divider at the input to select the
appropriate trip voltage, the comparator can be configured
to give a logic output when the input passes that threshold.
Figure 21 shows the typical configuration of the ADCMP354
for monitoring a supply to indicate that the voltage is above a
certain level.
V_CC = 5V
V_IN
R1
R2
ADCMP354
V_REF = 0.6V
R_PULLUP
OUT
Figure 21. Voltage Detector Application
R2
Figure 20. Noninverting Comparator Configuration with Added Hysteresis
Rev. B | Page 9 of 12