Power-On Time Power-on time depends to some extent on the device design. Here the device is off, and the output voltage V OUT , on the vertical axis depends on the device design: The branded face is where you will find the identification markings of the device, such as partial part number or date code. While the magnetic field remains more positive than B RP , the device remains turned-on, and the output state remains unchanged. This causes the output to change back to the original state.
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When the vehicle operator moves the lever, the magnet is alleyro past the individual Hall devices. The devices near the magnet are subjected to the magnetic field and are turned-on, but more remote devices are not affected and remain turned-off.
The magnet south pole is directed towards the branded face of the device package.
The following are terms used to define the transition points, or switchpointsof Hall switch operation:. B can have a north or south polarity, so it is useful to keep in mind the algebraic convention, by which B is indicated as a negative value for north-polarity magnetic fields, and as a positive value for south-polarity magnetic fields.
A single magnet presenting a south polarity positive magnetic field of sufficient strength magnetic flux density will cause the device to switch to its on state. When a unipolar switch turns on, the resulting output signal can be either at logic high or logic low, depending on the design of the device IC output stage.
Taken to the extreme, this can reduce the output voltage enough to inhibit proper external logic functions. Digital output devices, such as the unipolar switch, reach stability with the following approximate delays: Chopper-stabilized sensor ICs allow greater sensitivity with more-tightly controlled switchpoints than non-chopped designs. This causes the output voltage to change to the opposite state either to high or to low, depending on the device design.
Magnetic Switchpoint Terms The following are terms used to define the transition points, or switchpointsof Hall switch operation: Digital output wllegro, such as the unipolar switch, reach stability with the following approximate delays:. Following the arrows toward the right, the magnetic field becomes increasingly positive.
The top panel displays switching to logic low in the presence of a strong south polarity field, and the bottom panel displays switching to logic high, also in a south polarity field.
Here the device is off, and the output voltage V OUTon the vertical axis depends on the device design: After it has been turned-on, the unipolar IC will remain turned-on until the magnetic field is removed and the IC reverts to its alleggro state. There are four general categories of Hall-effect IC devices that provide a digital output: The distance from the branded face to the Hall element is referred to as the “active area depth.
Unipolar Hall-effect sensor ICs, often referred to as “unipolar switches,” are operated by a positive magnetic field. While the magnetic field remains more positive than B RPthe device remains turned-on, and the output state remains unchanged. When the magnetic field again drops below B RPthe device turns off. The gear-shift lever incorporates a magnet the red-and-blue cylinder.
The transfer function of a Hall device is designed with this offset between the switchpoints to filter out small fluctuations in the magnetic field that can result from mechanical vibration or electromagnetic noise in the application. Allegro unipolar devices are listed in the selection guides on the unippolar website, at Hall-Effect Unipolar Switches.
Allegro MicroSystems – Unipolar Hall-Effect Sensor IC Basics
When the field is more positive than B OPthe device turns on. Take this number to the derating chart in the datasheet for the package in question and check to see if the maximum allowable operational temperature must be reduced.
For example, for the “UA” package, the chip with the Hall element is 0. Typical Operation When a unipolar switch turns on, the resulting output signal can be either at logic high or logic low, depending on the design of the device IC qllegro stage. A “cleaner” signal is available when approaching from the package front side, because the Hall element is located closer to the front side the package branded face than to the back side.
Unipolar switch output characteristics. Basically, this means that prior to this elapsed time hnipolar providing power, device output may not be in the correct state, but after this time has elapsed, device output is guaranteed to be in the correct state. The minimum pull-up resistance is a function of the Hall IC maximum output current the devices usually are designed to sink unipolag and the supply voltage.
A very strong field will not damage an Allegro Hall-effect device nor uniplar such a field add additional switchpoint hysteresis other than the designed hysteresis.
Unipolar Hall-Effect Sensor IC Basics
The line of miniature black boxes is an array of unipolar switch devices. This convention allows arithmetic comparison of north and south polarity values, where the relative strength of the field is indicated by the absolute value of B, and the sign indicates the polarity of the field.
Jnipolar Hall effect refers to the measurable voltage present when an applied current is influenced by a perpendicular magnetic field.
