AS1970 데이터 시트보기 (PDF) - austriamicrosystems AG

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AS1970

Low-Voltage Single/Dual/Quad Comparators

austriamicrosystems AG 

AS1970

Data Sheet - Application Information

Hysteresis Band

Internal hysteresis creates two trip points (shown in Figure 20): rising input voltage (VTHR) and falling input voltage

(VTHF). The area between the trip points is the hysteresis band (VHB). When the comparator input voltages are equiva-

lent, the hysteresis effectively causes one comparator input to move quickly past the other, thus taking the input out of

the region where oscillation occurs.

In Figure 20 REF has a fixed voltage applied and IN+ is varied. If the inputs are reversed the output will be inverted.

Figure 20. Threshold Hysteresis Band

Thresholds

IN+

VTHR

REF

VTHF

VHB

OUT

Hysteresis

Band

Zero-Crossing Detector

Figure 21 shows the AS1970 in a zero-crossing detector circuit. The inverting input is connected to ground, and the

non-inverting input is connected to a 100mVp-p signal source. As the signal at the non-inverting input crosses 0V, the

signal at OUT changes states.

Figure 21. Zero-Crossing Detector

100mVp-p

3

IN+

4

IN-

2

VCC

+

–

AS1970

1

OUT

5

VEE

Logic Level Translator

The comparators can be used as a 5V/3V logic translator as shown in Figure 22. The circuit in Figure 22 converts 5V-

to 3V-logic levels, and provides the full 5V logic-swing without creating overvoltage on the 3V logic inputs. When the

comparator is powered by a 5V supply, RPULLUP for the open-drain output should be connected to the +3V supply volt-

age.

For 3V-to-5V logic-level translations, connect the +3V supply voltage to VCC and the +5V supply voltage to RPULLUP.

Figure 22. Logic Level Translator

+3/+5V

100kΩ

100kΩ

2

VCC

4

IN-

+5/+3V

3

Logic In IN+

AS1971

+

–

+3/+5V

1

OUT

5

VEE

RPullup

+5/+3V

Logic Out

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