VO

0

VIN2

VIN1

VIN

VO

VIN

VCC

VREF

-

+

R2

R1

LMV761, LMV762, LMV762Q-Q1

SNOS998I – FEBRUARY 2002 – REVISED OCTOBER 2015

www.ti.com

Feature Description (continued)

Hysteresis can easily be added to a comparator in a noninverting configuration with two resistors and positive

feedback Figure 22. The output will switch from low to high when VIN rises up to VIN1, where VIN1 is calculated by

Equation 1:

VIN1 = [VREF(R1 + R2)] / R2

(1)

The output will switch from high to low when VIN falls to VIN2, where VIN2 is calculated by Equation 2:

VIN2 = [VREF(R1 + R2) – (VCC R1)] / R2

(2)

The Hysteresis is the difference between VIN1 and VIN2, as calculated by Equation 3:

ΔVIN = VIN1 – VIN2 = [VREF(R1 + R2) / R2] – [VREF(R1 + R2)] – [(VCC R1) / R2] = VCC R1 / R2

(3)

Figure 21. Basic Comparator With Hysteresis

Figure 22. Noninverting Comparator Configuration

7.3.3 Input

The LMV76x devices have near-zero input bias current, which allows very high resistance circuits to be used

without any concern for matching input resistances. This near-zero input bias also allows the use of very small

capacitors in R-C type timing circuits. This reduces the cost of the capacitors and amount of board space used.

7.4 Device Functional Modes

7.4.1 Shutdown Mode

The LMV761 features a low-power shutdown pin that is activated by driving SD low. In shutdown mode, the

output is in a high-impedance state, supply current is reduced to 20 nA and the comparator is disabled. Driving

SD high will turn the comparator on. The SD pin must not be left unconnected due to the fact that it is a high-

impedance input. When left unconnected, the output will be at an unknown voltage. Do not three-state the SD

pin.

The maximum input voltage for SD is 5.5 V referred to ground and is not limited by VCC. This allows the use of

5-V logic to drive SD while VCC operates at a lower voltage, such as 3 V. The logic threshold limits for SD are

proportional to VCC.

12

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