AMC22C11 datasheet(13/33 Pages) TI

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7.3 Feature Description

7.3.1 Analog Input

The comparator trips when the input voltage (VIN) rises above the VIT+ threshold that is defined as the reference

value plus the internal hysteresis voltage. The comparator releases when VIN drops below the VIT– threshold that

equals the reference value.

The difference between VIT+ and VIT– is referred to as the comparator hysteresis and is 4 mV for reference

voltages below 450 mV. The integrated hysteresis makes the AMC22C11 less sensitive to input noise and

provides stable operation in noisy environments without having to add external positive feedback to create

hysteresis. The hysteresis increases to 25 mV for reference values (VREF) greater than 600 mV. See the

Reference Input description for more details.

Figure 7-1 shows a timing diagram of the relationship between hysteresis and switching thresholds.

VIN

OUT

VIT+

VIT– (VREF)

VHYS

0 V

LATCH

Figure 7-1. Switching Thresholds and Hysteresis

7.3.2 Reference Input

The voltage on the REF pin determines the trip threshold of the comparator. The internal precision current

source forces a 100-μA current through an external resistor connected from the REF pin to GND1. The resulting

voltage across the resistor (VREF) equals the trip threshold, see Figure 7-1. Place a 100-nF capacitor parallel to

the resistor to filter the reference voltage. This capacitor must be charged by the 100-μA current source during

power-up and the charging time may exceed the high-side blanking time (tHS,BLK). In this case, as shown in

Figure 7-2, the comparator may output an incorrect state after the high-side blanking time has expired until

VREF reaches its final value. See the Power-Up and Power-Down Behavior section for more details on power-up

behavior.

tHS, STA + tHS,BLK

OUT

VREF settling time

low

Output not valid

Output valid

VREF

VDD2

VDD1

<1%

OUT not valid

if VIN is in this range

during power-up

Figure 7-2. Output Behavior for Long Settling Times of the Reference Voltage

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AMC22C11

SBASAJ6 – APRIL 2022

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