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HMC1021D 参数 Datasheet PDF下载

HMC1021D图片预览
型号: HMC1021D
PDF下载: 下载PDF文件 查看货源
内容描述: 1和2轴磁传感器 [1- and 2-Axis Magnetic Sensors]
分类和应用: 传感器
文件页数/大小: 15 页 / 628 K
品牌: HONEYWELL [ Honeywell ]
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LINEAR MAGNETIC FIELD SENSORS  
BASIC DEVICE OPERATION  
The OFFSET strap allows for several modes of operation  
when a dc current is driven through it.  
Honeywell magnetoresistive sensors are simple resistive  
bridge devices (Figure 1) that only require a supply voltage  
to measure magnetic fields. When a voltage from 0 to 10  
volts is connected to Vbridge, the sensor begins measuring  
any ambient, or applied, magnetic field in the sensitive axis.  
In addition to the bridge circuit, the sensor has two on-chip  
magnetically coupled strapsthe OFFSET strap and the  
Set/Reset strap. These straps are patented by Honeywell  
andeliminatetheneedforexternalcoilsaroundthedevices.  
An unwanted magnetic field can be subtracted out  
The bridge offset can be set to zero  
The bridge output can drive the OFFSET strap to cancel  
outthefieldbeingmeasuredinaclosedloopconfiguration  
The bridge gain can be auto-calibrated in the system on  
command.  
Vbridge  
TheSet/Reset(S/R)strapcanbepulsedwithahighcurrentto:  
(7)  
3.5 max.  
OFFSET +  
(2)  
OFFSET -  
(6)  
R
R
R
R
Force the sensor to operate in the high sensitivity mode  
Flip the polarity of the output response curve  
Be cycled during normal operation to improve linearity  
and reduce cross-axis effects and temperature effects.  
Ioffset  
R=600-1200 Ω  
2.0 max.  
OUT+  
(5)  
OUT-  
(8)  
S/R +  
(1)  
S/R -  
(3)  
Iset, -Ireset  
GND  
(4)  
The output response curves shown in Figure 2 illustrate the  
effects of the S/R pulse. When a SET current pulse (Iset) is  
drivenintotheSR+pin,theoutputresponsefollowthecurve  
with the positive slope. When a RESET current pulse  
(Ireset) is driven into the SR- pin, the output response follow  
the curve with the negative slope. These curves are mirror  
images about the origin except for two offset effects.  
Figure 1On-Chip components (HMC1001)  
Magnetoresistive sensors are made of a nickel-iron  
(Permalloy) thin film deposited on a silicon wafer and  
patterned as a resistive strip. In the presence of an applied  
magnetic field, a change in the bridge resistance causes a  
corresponding change in voltage output.  
In the vertical direction, the bridge offset shown in Figure 2,  
isaround-25mV. Thisisduetotheresistormismatchduring  
themanufactureprocess.Thisoffsetcanbetrimmedtozero  
by one of several techniques. The most straight forward  
technique is to add a shunt (parallel) resistor across one leg  
of the bridge to force both outputs to the same voltage. This  
must be done in a zero magnetic field environment, usually  
in a zero gauss chamber.  
An external magnetic field applied normal to the side of the  
film causes the magnetization vector to rotate and change  
angle.Thisinturnwillcausetheresistancevaluetovary(R/  
R) and produce a voltage output change in the Wheatstone  
bridge.ThischangeinthePermalloyresistanceistermedthe  
magnetoresistive effect and is directly related to the angle of  
the current flow and the magnetization vector.  
The offset of Figure 2 in the horizontal direction is referred to  
hereastheexternaloffset.Thismaybeduetoanearbyferrous  
object or an unwanted magnetic field that is interfering with the  
applied field being measured. A dc current in the OFFSET  
strap can adjust this offset to zero. Other methods such as  
shielding the unwanted field can also be used to zero the  
external offset. The output response curves due to the SET  
and RESET pulses are reflected about these two offsets.  
During manufacture, the easy axis (preferred direction of  
magnetic field) is set to one direction along the length of the  
film. This allows the maximum change in resistance for an  
appliedfieldwithinthepermalloyfilm.However,theinfluence  
of a strong magnetic field (more than 10 gauss) along the  
easy axis could upset, or flip, the polarity of film  
magnetization, thus changing the sensor characteristics.  
Following such an upset field, a strong restoring magnetic  
field must be applied momentarily to restore, or set, the  
sensor characteristics. This effect will be referred to as  
applying a set pulse or reset pulse. Polarity of the bridge  
outputsignaldependsuponthedirectionofthisinternalfilm  
magnetization and is symmetric about the zero field output.  
40  
Vcc=8V  
(1001/1002)  
20  
0
response  
after Iset  
response  
after Ireset  
bridge  
offset  
-20  
-40  
-60  
-80  
external  
offset  
Applied Field (Gauss)  
Figure 2Output Voltage vs. Applied Magnetic Field  
6