Datasheet > LMV7251MDC

LMV7251MDC

更新时间： 2024-02-02 19:58:40

品牌	Logo	应用领域
美国国家半导体 - NSC		/
页数	文件大小	规格书
17页	303K
描述
IC COMPARATOR, 6000 uV OFFSET-MAX, 670 ns RESPONSE TIME, UUC, DIE, Comparator

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LMV7251MDC 数据手册

hysteresis causes one input to effectively move quickly pass

the other. Thus, effectively moving the input out of region that

oscillation may occur.

Application Info

Basic Comparators

A comparator is quite often used to convert an analog signal

to a digital signal. The comparator compares an input volt-

age (V_IN) at the non-inverting pin to the reference voltage

(V_REF) at the inverting pin. If V_INis less than V_REFthe output

(V_O) is low (V_OL). However, if V_INis greater than V_REF, the

output voltage (V_O) is high (V_OH).

Hysteresis can easily be added to a comparator in a

non-inverting configuration with two resistors and positive

feedback Figure 3. The output will switch from low to high

when V_INrises up to V_IN1, where V_IN1is calculated by

V_IN1= (V_REF(R1 + R2))/ R2

The output will switch from high to low when V_INfalls to V_IN2

where V_IN2is calculated by

LMV7251

V_IN2= (V_REF(R1 + R2) - V_CCR1) / R2

The Hysteresis is the difference between V_IN1and V_IN2

∆V_IN= V_IN1- V_IN2= ((V_REF(R1 + R2)) / R2) - ((V_REF(R1 +

R2) - V_CCR1) / R2) = V_CCR1/ R2.

DS200057-15

LMV7255

DS200057-18

DS200057-16

Input/Output

DS200057-19

FIGURE 3. Non-Inverting Comparator Configuration —

LMV7251

For an inverting configured comparator, hysteresis can be

added with a three resistor network and positive feedback.

When input voltage (V_IN) at the inverting node is less than

non-inverting node (V_T), the output is high. The equivalent

circuit for the three resistor network is R1 in parallel with R3

and in series with R2. The lower threshold voltage V_T1is

calculated by:

DS200057-17

FIGURE 2. Basic Comparator

Hysteresis

V_T1= ((V_CCR2) / ((R1 R3) / (R1+ R3)) + R2)

The basic comparator configuration may oscillate or produce

a noisy output if the applied differential input is near the

comparator’s input offset voltage. This tends to occur when

the voltage on the input is equal or very close to the other

input voltage. Adding hysteresis can prevent this problem.

Hysteresis creates two switching thresholds (one for the

rising input voltage and the other for the falling input volt-

age). Hysteresis is the voltage difference between the two

switching thresholds. When both inputs are nearly equal,

When V_INis greater than V_T, the output voltage is low. The

equivalent circuit for the three resistor network is R2 in

parallel with R3 and in series with R1. The upper threshold

voltage V_T2is calculated by:

V_T2= V_CC((R2 R3) / (R2 + R3)) / ((R1 + ((R2 R3) / (R2 +

R3))

The hysteresis is defined as

∆V_IN= V_T1- V_T2= ((V_CCR2) / ((R1 R3) / (R1+ R3)) + R2) –

(V_CC((R2 R3) / (R2 + R3)) / ((R1 + ((R2 R3) / (R2 + R3)))

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