ALLEGRO UNIPOLAR DRIVER

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. Note that the south pole of the magnet colored red is toward the Hall devices, and that the Hall devices are oriented with the branded face of the device toward the magnet south pole. When the magnetic field again drops below B RP , the device turns off. Allegro unipolar devices are listed in the selection guides on the company website, at Hall-Effect Unipolar Switches. Following the arrows toward the right, the magnetic field becomes increasingly positive.

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Power-on time depends to some extent on the device design. A single magnet presenting a umipolar polarity positive magnetic field of sufficient strength magnetic flux density will cause the device to switch to its on state.

Taken to the extreme, this can reduce the output voltage enough to inhibit proper external logic functions.

A very strong field will not damage an Allegro Hall-effect device nor will such a field add additional switchpoint hysteresis other than the designed hysteresis. An application for detecting the position of a vehicle gear-shift lever is shown in figure 1.

Power-On Time Power-on time depends to some extent on the device design. Unipolar switch output characteristics. The north pole would then generate a positive field relative to the Hall element, while the south pole would generate a negative field. This causes the output to change back to the original state. Unipolar Hall-effect sensor ICs, often referred to as “unipolar switches,” are operated by a positive magnetic field.

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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.

This is not a device problem, rather the leakage occurs in the conductors between the pull-up resistor and the device output pin. Basically, this means that prior allehro this elapsed time after 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.

Allegro MicroSystems – Unipolar Hall-Effect Sensor IC Basics

For example, for the “UA” package, the chip with the Hall element is 0. There are four general categories of Hall-effect IC devices that provide a digital output: Note that the south pole of the magnet colored red is toward the Hall devices, and that the Hall devices are oriented with the branded face of the device toward the magnet south pole.

The unpiolar from the branded face to the Hall element is referred to as the “active area depth. Unipolar switches are described in this application note. This convention allows arithmetic comparison of north and south polarity values, where the relative strength of the field is indicated unpiolar the absolute value of B, and the sign indicates the polarity of the field.

Unipolar Hall-Effect Sensor IC Basics

The line of miniature black boxes is an array of unipolar switch devices. The ultra-small Hall ICs switch as the magnet red and blue cylinder moves past them during gear-shifting. Allegro unipolar devices are listed in the selection guides on the company website, at Hall-Effect Unipolar Switches.

Digital output devices, such as the unipolar switch, reach stability with the following approximate delays: The resulting state of the device output depends on the individual device electronic design.

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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 output stage.

The branded face is where you will find the identification markings of the device, such as partial part number or date code.

An application using unipolar switch sensor ICs. The Hall effect refers to the measurable voltage present when an applied current is influenced by a perpendicular magnetic field. These currents could be high enough to reduce the output voltage, regardless of the state of the magnetic field and device switching state. This causes the output voltage to change to the opposite state either to high or to low, depending on the device design.

Yes, however bear this in mind: Most new device designs utilize a chopped Hall element. When the field is more positive than B OPthe device turns on.

The magnet south pole is directed towards the branded face of the device package.

Chopper-stabilized sensor ICs allow greater sensitivity with more-tightly controlled switchpoints than non-chopped designs. The minimum pull-up resistance is a function of the Hall IC maximum output current the devices usually are designed to sink current and the supply voltage.

Take alllegro 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.