LMV7275-Q1 Datasheet, PDF (15/31 Pages) Texas Instruments – Automotive Single 1.8-V Low Power Comparator With Rail-to-Rail Input

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LMV7275-Q1
SNOSD09 – SEPTEMBER 2015
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 −300 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.
7.4.5 Threshold Detector
V_IN
V_D
R₁
+
V_REF
R₂
R_PULL-UP
V_OUT
Figure 24. Threshold Detector
Instead of tying the inverting input to 0 V, the inverting input can be tied to a reference voltage. As the input on
the Non-Inverting input passes the V_REF threshold, the output of the comparator changes state. It is important to
use a stable reference voltage to ensure a consistent switching point.
7.4.6 Universal Logic Level Shifter
V_A
V_CC
V_B
10 NŸ
10 NŸ
Logic
In
R_PULL-UP
+
Logic
Out
V_B ”9_CC
Figure 25. Logic Level Shifter
The output of LMV7275-Q1 is an unconnected drain of an NMOS device, which can be pulled up, through a
resistor, to any desired output level below the comparators power supply voltage (V_B ≤ V_CC). Hence, the following
simple circuit works as a universal logic level shifter, pulling up the signal to the desired level.
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