LMV331, NCV331, LMV393, LMV339
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12
VO HIGH
+VCC
R3
VT1
R1
R2
Figure 22.
VO LOW
+VCC
R3
VT2
R1
R2
Figure 23.
Noninverting Configuration with Hysteresis
A noninverting comparator is shown in Figure
24.Figure 24.
+VCC
VREF
+
R2
VIN
R1
VA
RPULLUP
VO
RLOAD
The hysteresis band (Figure
25) of the noninverting
configuration is defined as follows:
DVin + VCCR1 R2
VIN1
VIN2
VIN
VO
VCC
0
Figure 25.
When VIN is much less than the voltage at the inverting
input (VREF), then the output is low. R2 can then be viewed
as being connected to ground (Figure
26). To calculate the
voltage required at VIN to trip the comparator high, the
following equation is used:
Vin1 +
Vref (R1 ) R2)
R2
When the output is high, VIN must less than or equal to
VREF (VIN ≤ VREF) before the output will be low again
(Figure
27). The following equation is used to calculate the
voltage at VIN to switch the output back to the low state:
Vin2 +
Vref (R1 ) R2) * VCCR1
R2
R2
R1
VA = VREF
VIN2
VO HIGH
+VCC
Figure 26.
R1
R2
VA = VREF
VO LOW
VIN1
Figure 27.
Termination of Unused Inputs
Proper termination of unused inputs is a good practice to
keep the output from ‘chattering.’ For example, if one
channel of a dual or quad package is not being used, then the
inputs must be connected to a defined state. The
recommended connections would be to tie one input to VCC
and the other input to ground.