ADXL50 データシートの表示（PDF） - Analog Devices

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ADXL50

Monolithic Accelerometer With Signal Conditioning

Analog Devices 

ADXL50

DENOTES EXTERNAL

PIN CONNECTION

C2

+3.4V

75Ω

EXTERNAL

OSCILLATOR

DECOUPLING

CAPACITOR

1MHz

OSCILLATOR

0°

180°

+5V

VREF

+3.4V

+5V

+5V

INTERNAL

REFERENCE

SYNC

COMMON

+3.4V +1.8V +0.2V

COM

+3.4V

CS1

BEAM

CS2

+0.2V

+1.8V

VIN–

+1.8V

3MΩ

+5V

33kΩ

33kΩ

C1

EXTERNAL

C1

DEMODULATION

CAPACITOR

PREAMP

VPR

SYNCHRONOUS

DEMODULATOR

+1.8V

LOOP GAIN = 10

INTERNAL

FEEDBACK

LOOP

RST

BUFFER

AMPLIFIER

VOUT

50kΩ

SELF–TEST

(ST)

+3.4V

Figure 18. Functional Block Diagram

The sensor’s tight mechanical spacing allows it to be electro-

statically deflected to full scale while operating on a 5 volt sup-

ply. A self-test is initiated by applying a TTL “high” level

voltage (>+2.0 V) to the ADXL50’s self-test pin which causes

the chip to apply a deflection voltage to the beam which moves

it an amount equal to –50 g (the negative full-scale output of the

device). Note that the ± 10% tolerance of the self-test circuit is

not proportional to the sensitivity error, see Self-Test section.

The output of the ADXL50’s preamplifier is 1.8 V at 0 g accel-

eration with an output range of ± 0.95 V for a ± 50 g input, i.e.,

19 mV/g. An uncommitted buffer amplifier has been included

on-chip to enhance the user’s ability to offset the 0 g signal level

and to amplify and filter the signal. Access is provided to both

the inverting input and the output of this amplifier via pins

VOUT and VIN–, while the noninverting input is connected inter-

nally to a +1.8 V reference. The +1.8 V is derived from a

resistor divider connected to the 3.4 V reference.

BASIC CONNECTIONS FOR THE ADXL50

Figure 19 shows the basic connections needed for the ADXL50

to measure accelerations in the ± 50 g range with an output scale

factor 40 mV/g corresponding to a 2.5 V 0 g level, a ± 2.0 V full-

scale swing around 0 g and a 3 dB bandwidth of approximately

1 kHz.

In general, the designer will need to take into account the initial

zero g bias when designing circuits. For the ADXL50J this off-

set is 1.8 V ± 250 mV. When microprocessors and software

REV. B

OSCILLATOR

DECOUPLING

CAPACITOR

4

C2

0.022µ F

OSCILLATOR

SELF TEST

(ST)

7

ADXL50

REFERENCE

+1.8V

+3.4V

6

VREF

OUTPUT

SENSOR

DEMODULATOR

PREAMP

BUFFER

AMP

5

COM

1

C3

+5V

2

C1

3

C1

0.022µF

DEMODULATOR

CAPACITOR

8

VPR

10

9

VIN– R3

105kΩ

R1

49.9kΩ

R2

274kΩ

VOUT

Figure 19. ADXL50 Application Providing an Output Sensitivity of

40 mV/g, a +2.5 V 0 g Level and a Bandwidth of 1 kHz

–9–

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