LMV7235_16 Datasheet, PDF (14/30 Pages) Texas Instruments – 75-ns, Ultra Low Power, Low Voltage, Rail-to-Rail Input Comparator with Open-Drain and Push-Pull Output

LMV7235, LMV7239, LMV7239-Q1
SNOS532N – SEPTEMBER 2000 – REVISED APRIL 2015
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Device Functional Modes (continued)
The positive feedback resistor, R₆, is made very large with respect to R₅ || R₆ = 2000 R₅). The resultant
hysteresis established by this network is very small (ΔV₁ < 10 mV) but it is sufficient to insure rapid output
voltage transitions.
Diode D₁ is used to insure that the inverting input terminal of the comparator never goes below approximately
−100 mV. As the input terminal goes negative, D₁ will forward bias, clamping the node between R₁ and R₂ to
approximately −700 mV. This sets up a voltage divider with R₂ and R₃ preventing V₂ from going below ground.
The maximum negative input overdrive is limited by the current handling ability of D₁.
V_CC
R3
R₄
R₁
R₂
V_IN
-
V₂
V_O
D1
V₁
+
R₆
R₅
Figure 22. Zero Crossing Detector with Hysteresis
8.4.5 Threshold Detector
Instead of tying the inverting input to 0V, the inverting input can be tied to a reference voltage. As the input on
the non-inverting input passes the V_REF threshold, the comparator’s output changes state. It is important to use a
stable reference voltage to ensure a consistent switching point.
Figure 23. Threshold Detector
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