2. Functional Description
The Si7201/2/3/4/5/6 family of Hall Effect magnetic sensors digitize the component of the magnetic field in the z axis of the device (pos-
itive field is defined as pointing into the device from the bottom). The digitized field is compared to a pre-programmed threshold and the
output pin goes high or low if the threshold is crossed. The parts are normally used to detect the presence or absence of a magnet in
security systems, as position sensors or for counting revolutions.
Table 2.1. Part Ordering Guide
Part Number Description
Si7201 Low voltage switches
Si7202 Low voltage latches
Si7203 Low voltage switch with tamper and/or disable pins
Si7204 Low voltage latches with tamper and/or disable pins
Si7205 High voltage switches
Si7206 High voltage latches
The output pin (push pull or open collector) can go high or low when the magnetic field crosses a threshold. The output pin configura-
tion is determined by the type of part ordered.
The parts are preconfigured for the magnetic field measurement range, magnetic field operate and release points, sleep time, tempera-
ture compensation, tamper threshold and digital filtering and will wake into this mode when first powered. The specific configuration
output type (open collector or push pull) are determined by the part number.
Following is a list of configuration options:
• Measurement Range: This is normally set so that after temperature compensation the full scale output is ±20.47 mT or ±204.7 mT
For convenience these are referred to as the 20 mT and 200 mT scales
• Decision Points:
• For 20 mT switch mode parts, the middle of the decision point can be configured from 0.08 mT to 19.2 mT. For 200 mT parts, the
middle point of the decision threshold can be programmed from 0.8 mT to 192 mT
• For latch mode parts the middle of the decision point is zero.
• For 20 mT scale switch mode parts, the hysteresis can be programmed to ±0.04 mT to ±8.96 mT. On the 200 mT scale, these
numbers are multiplied by 10.
• For latch mode parts the decision points can be configured from ±0.08 mT to ±17.92 mT on the 20 mT scale. On the 200 mT
scale these numbers are multiplied by 10.
• For 20 mT scale parts, the tamper threshold can be configured from 2.65 mT to 19.84 mT. On the 200 mT scale these numbers
are multiplied by 10. Tamper detection can also be disabled.
• Digital Filtering: To reduce noise in the output (normally 0.03 mT RMS on the 20 mT scale), digital filtering can be applied. The digi-
tal filtering can be done to a burst a measurements (FIR filter) or can be configured to average measurements in IIR style. The filter-
ing can be done over a number of samples in powers of 2 (1,2,4,8,…) for up to 2
12
(4096) samples
• Time between Measurements (or Measurement Bursts for the Case of FIR Filtering):
• For lowest power, the part can be configured to sleep between measurements. Sleep times are configurable from 1 msec to 200
msec.
• For faster measurement rates and for analog output mode the part is configured to idle between samples. Idle times are variable
from 13.2 μsec to 206 msec nominally.
• The Digital Output Pin:
• The direction in which the output pin goes in response to an increase in field
• There is an option to take the magnitude of the field prior to the comparison so that the polarity is not field dependent
• For 3 pin parts in the case of tamper detection the output pin will go to its zero field value (which in security systems is normally
an indication of door or window open).
• For 4 and 5 pin parts there is a separate tamper indication pin
• Temperature compensation of the magnetic field response to compensate for the nominal drop in magnetic field output of common
magnets with increasing temperature.
Note: In this case accuracy is defined at 25°C and the sensitivity increases at higher temperature
Si720x Switch/Latch Hall Effect Magnetic Position Sensor Data Sheet
Functional Description
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