Hall-effect ICs sleep to save power

Sensor ICs provide a voltage output that is directly proportional to an applied magnetic field

The A139x family of linear Hall effect sensor ICs from Allegro MicroSystems Europe combines micropower operation, a tristate output and a user-selectable sleep mode. The new sensor ICs provide a voltage output that is directly proportional to an applied magnetic field. The sleep mode allows the devices to operate at a current consumption of less than 25uA, which contrasts with typical Hall-effect ICs whose sensitivity before amplification is directly proportional to the current flowing through the transducer element.
As a result, it is difficult to achieve sufficient sensitivity levels with traditional Hall-effect sensor ICs without consuming more than 3mA of current.

This low-current operation and the resulting power consumption of less than 10mW makes these devices perfect for battery-operated applications such as mobile telephones, digital cameras, and portable tools.

The operating voltage of 3V makes them compatible with 2.5-3.5V supplies.
There are four devices in the family, differentiated only by sensitivity: A1391, 1.25mV/Gs; A1392, 2.5mV/Gs; A1393, 5mV/Gs; and A1395, 10mV/Gs.

Despite the low power consumption of the circuitry in the A139x family, the features required to produce a highly accurate linear Hall effect IC have not been compromised.

Each BiCMOS monolithic circuit integrates a Hall element, improved temperature-compensating circuitry to reduce the intrinsic sensitivity drift of the Hall element, a small-signal high-gain amplifier, and proprietary dynamic offset cancellation circuits.

End-of-line post-packaging factory programming allows precise control of device sensitivity and offset.

End users can control the current consumption of the A139x by applying a logic level signal to the sleep pin.

The outputs of the devices are not valid during sleep mode, when they switch to high-impedance mode.

The high-impedance output feature allows the connection of multiple A139x Hall-effect devices to a single A/D convertor input.

The quiescent output voltage of these devices is 50% nominal of the ratiometric supply reference voltage applied to the reference pin of the device.

The new sensors will operate over a wide ambient temperature range from -20 to +85C, and feature electrostatic discharge protection of greater than 3kV.

The A1391x Series devices are available in a small (2.0 x 3.0 x 0.75mm) microleaded MLP/DFN package.