RHR801 datasheet(24/32 Pages) STMICROELECTRONICS

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Parameters and implementation

RHR801

5.6

Application examples

5.6.1

Inverting comparator with hysteresis

The RHR801 comparator has a typical 2.5 mV implemented input voltage hysteresis which

improves device stability and ensures a clean output response when the input signal

amplude is relative small or moving slowly. However, in certain situations, like in noisy

environments, it is desirable to increase the hysteresis value. This can easily be done by

an external positive feedback network connected to the device.

Figure 44: External hysteresis circuit

Figure 44 shows the circuit with positive feedback between the output and non-inverting

input. Threshold voltages are given by the R1, R2, and R3 ratio and the VCC power supply

voltage. Neglecting input bias current and output voltage drop, VTH+, and VTH- can be

calculated using Equation 1.

Equation 1

The symbol “|” represents a resistors parallel combination. The threshold voltages of Figure

44 are set to VTH+ = 1.1 V and VTH- = 1.3 V.

5.6.2

Fast signal recovery

The circuit in Figure 45 represents an example of a simple translator input signal from a 50

Ω transmission line to a CMOS compatible output.

OUT

100n

9.1k

2.7k

VOL

VOH

VIN

VOUT

VTH+ VTH-

RHR801

3 V to 5 V

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