ADCMP394 datasheet(12/18 Pages) AD

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ADCMP394/ADCMP395/ADCMP396

Data Sheet

Rev. B | Page 12 of 18

TYPICAL APPLICATIONS

ADDING HYSTERESIS

To add hysteresis, see Figure 33; two resistors are used to create

different switching thresholds, depending on whether the input

signal is increasing or decreasing in magnitude. When the input

voltage increases, the threshold is above VREF, and when the

input voltage decreases, the threshold is below VREF.

Figure 33. Noninverting Comparator Configuration with Hysteresis

The upper input threshold level is given by

REF

IN_HI

)

(





(2)

Assuming RLOAD >> R2, RPULLUP.

The lower input threshold level is given by



PULLUP

REF









(3)

The hysteresis is the difference between these voltages levels.

)

(

PULL

REF

HYS













)

(

)

(

(4)

WINDOW COMPARATOR FOR POSITIVE VOLTAGE

MONITORING

When monitoring a positive supply, the desired nominal

operating voltage for monitoring is denoted by VM, IM is the

nominal current through the resistor divider, VOV is the

overvoltage trip point, and VUV is the undervoltage trip point.

Figure 34. Positive Undervoltage/Overvoltage Monitoring Configuration

Figure 34 illustrates the positive voltage monitoring input

connection. Three external resistors, RX, RY, and RZ, divide the

positive voltage for monitoring, VM, into the high-side voltage,

VPH, and the low-side voltage, VPL. The high-side voltage is

connected to the INA+ pin and the low-side voltage is

connected to the INB− pin.

To trigger an overvoltage condition, the low-side voltage (in

this case, VPL) must exceed the VREF threshold on the INB+ pin.

Calculate the low-side voltage, VPL, by the following:

















REF

(5)

In addition,

RX + RY + RZ = VM/IM

(6)

Therefore, RZ, which sets the desired trip point for the

overvoltage monitor, is calculated as



 



REF

R 

(7)

To trigger the undervoltage condition, the high-side voltage,

VPH, must be less than the VREF threshold on the INA− pin. The

high-side voltage, VPH, is calculated by

















REF

(8)

Because RZ is already known, RY can be expressed as



 

 Z

REF





(9)

When RY and RZ are known, RX can be calculated by

RX = (VM/IM) – RY − RZ

(10)

If VM, IM, VOV, or VUV changes, each step must be recalculated.

OUTx

INx–

INx+

VREF = 2.5V

VIN

VCC = 5V

RLOAD

RPULL-UP

VOUT

VIN

VIN_LOW VIN_HIGH

OUTA

INA+

INA–

REF

OUTB

INB+

INB–

VPL

VPH

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