A3054 데이터 시트보기 (PDF) - Allegro MicroSystems

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A3054

MULTIPLEXED TWO-WIRE HALL-EFFECT SENSOR ICs

Allegro MicroSystems 

3054

MULTIPLEXED

TWO-WIRE

HALL-EFFECT SENSOR ICs

Bus Driver

It is recommended that the bus be controlled

by microprocessor-based hardware for the

following reasons:

• Sensor address information may be stored

in ROM in the form of a look-up table.

• Bus faults can be pinpointed by the

microprocessor by comparing the diagnos-

tic response to the expected response in

the ROM look-up table.

• The microprocessor, along with an A/D

converter, can also be used to self cali-

brate the quiescent currents in the bus and

hence be able to easily detect a signal

response.

• The microprocessor can also be used to filter out random line noise

by digitally filtering the bus responses.

• The microprocessor can easily keep track of the signal responses

and initiate the appropriate action (e.g., light a lamp or sound an

alarm, and also pinpoint the location of the signal).

Optimally, the microprocessor is used to control bus-driving

circuitry that will accept TTL-level inputs to drive the bus and will return

an analog voltage representation of the bus current.

Interface Schematic

The bus driver is easily designed using a few operational amplifi-

ers, resistors, and transistors. Figure 4 shows a schematic of a

recommended bus driver circuit that is capable of providing 6 V to 9 V

transitions, resetting the bus, and providing an analog measurement of

the bus current for the A/D input of the microprocessor.

+15 V

1 kΩ

10 kΩ R 4

9V

0.001

Z1

µF

20 kΩ

R5

ADDRESS 5 kΩ

Q1

RESET 5 kΩ

FIGURE 4

BUS INTERFACE SCHEMATIC

1 kΩ

Q3

OP 1

50 Ω R 6

Q2

50 kΩ

R8

BUS SUPPLY

X

X

50 kΩ

R7

12 3

NC

100 kΩ R 9

12 3

SWITCH

BUS RETURN

100 kΩ

R 10

OP 2

ANALOG OUT

Dwg. EH-003A

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