LPV7215 datasheet(14/28 Pages) TI1

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VIN1 =

VREF (R1 + R2)

'VA =

+VCCR1R2

R1R2 + R1R3 + R2R3

LPV7215

SNOSAI6I – SEPTEMBER 2005 – REVISED APRIL 2013

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INVERTING COMPARATOR WITH HYSTERESIS

The inverting comparator with hysteresis requires a three resistor network that is referenced to the supply voltage

V+ of the comparator as shown in Figure 34. When VIN at the inverting input is less than VA, the voltage at the

non-inverting node of the comparator (VIN < VA), the output voltage is high (for simplicity assume VO switches as

high as V+). The three network resistors can be represented as R1//R3 in series with R2.

The lower input trip voltage VA1 is defined as

VA1 = VCCR2 / ((R1//R3) + R2)

When VIN is greater than VA, the output voltage is low or very close to ground. In this case the three network

resistors can be presented as R2//R3 in series with R1.

The upper trip voltage VA2 is defined as

VA2 = VCC (R2//R3) / ((R1+ (R2//R3)

The total hysteresis provided by the network is defined as

ΔVA = VA1 - VA2

Figure 34. Inverting Comparator with Hysteresis

NON-INVERTING COMPARATOR WITH HYSTERESIS

A non-inverting comparator with hysteresis requires a two resistor network, and a voltage reference (VREF) at the

inverting input. When VIN is low, the output is also low. For the output to switch from low to high, VIN must rise up

to VIN1 where VIN1 is calculated by.

As soon as VO switches to VCC, VA will step to a value greater than VREF, which is given by

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