ADAF1080BCPZ datasheet(20/36 Pages) AD

20 / 36 page

Data Sheet

ADAF1080

THEORY OF OPERATION

analog.com

Rev. 0 | 20 of 36

The ADAF1080 provides a completely coreless solution for wide

range low-noise and low-hysteresis magnetic field measurements,

with reduced package size and current consumption. Unlike tradi-

tional Hall-based magnetic field sensors, the ADAF1080 does not

require a magnetic core or flux concentrator.

The ADAF1080 includes the following in a single package:

►

An AMR sensor with an electrical-offset cancellation capability

provided through an integrated flip coil

►

An integrated, precision, zero-drift instrumentation amplifier and

ADC driver for signal conditioning

►

Digital circuitry for additional functionality such as gain control,

temperature compensation, electrical-offset cancellation, and

clock synchronization

AMR MAGNETIC FIELD SENSOR

The integrated AMR magnetic field sensor is composed of four

AMR elements in a Wheatstone bridge configuration. The output

voltage of the Wheatstone bridge changes when the elements

sense a magnetic field along the sense field axis as shown in

Figure 42. The cross field axis of the sensor is the long axis of

the AMR elements. The bridge output is then amplified by the inte-

grated signal conditioning circuit (see the Integrated Signal-Chain

Conditioning section). The bridge supply is driven by the internal

bridge driver circuit that keeps the bridge supply proportional to

VDD.

The transfer function of the ADAF1080 can be described by the

following equation:

VOUT= BSENSE×SDEVICE ×VDD5+VSET2 (1)

where:

VOUT is the measured output of the ADAF1080 on the VOUT pin.

BSENSE is the magnetic field along the sense field axis.

SDEVICE is the sensitivity of the device due to a magnetic field on

the sense field axis.

VDDis the voltage on the VDD pin.

VSETis the voltage on the VSET pin.

Figure 42. AMR Sensor Bridge and Flip Coil

A short high-current pulse is applied on the flip coil by the flip coil

driver circuitry to generate a strong, localized magnetic field at the

AMR sensor elements to align the internal magnetic domains of

the sensor to set its sensitivity polarity. Changing the polarity of

this current pulse reverses the magnetic domains of the sensor

along the easy axis, as shown in Figure 43, which can be used

for electrical-offset measurement and cancellation (see the Flip Coil

and Flip Coil Driver section). The flip coil can also be used after a

saturation event to realign the magnetic domain along the easy axis

and to reset the sensitivity polarity.

Figure 43. Effect of the Flip Coil to Align the Magnetic Domains of the Sensor

SENSE FIELD AXIS

The integrated AMR sensor in the ADAF1080 produces an analog

output that is proportional to the magnetic field strength on a single

axis in the plane of the package. This AMR sensor is capable of

sensing over a wide magnetic field up to ±8 mT.

The sense field axis of the ADAF1080 is shown in Figure 44 and is

referenced by Pin 1 of the lead frame chip-scale package.

ADAF1080BCPZ датащи(PDF) 20 Page - Analog Devices

ADAF1080BCPZ датащи(HTML) 20 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

датащи скачать

ссылки URL