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How Tiny Hall Switches Save Space in Portable Devices

AH138x and AH139x Hall Effect Switches

By Charles Kuo, Product Line Manager

The electronics industry possesses a never-ending drive for lower power consumption and more compact devices. It is most obvious in battery-powered consumer products, such as wearables, smartphones, and wireless earbuds. The demands for smaller and power-efficient solutions hold true almost everywhere—across home appliances, industrial applications, data centers, and more.

Every component in a system design needs to be analyzed in terms of these two objectives: “can it be smaller”, and “can it use less power”. At the same time, we can’t compromise on performance, reliability, and cost. For switches in portable, battery-powered devices, the solution to meeting these challenges is often to use a Hall-effect sensor—yearly sales of over $1.5 billion[1] show how popular this type of component is.

These sensors are based on the Hall effect: when a current is applied to a strip of metal in the presence of a magnetic field, a voltage difference is produced at right angles to the current. This voltage is proportional to the strength of the magnetic field. Hall sensors are ideal for use in many types of switches, where they can simply detect the presence or absence of a small permanent magnet. They are often used in proximity sensing applications, such as detecting whether a laptop’s lid is open or closed. Since the switches are contactless, they are reliable and have a long operating life.

To meet the demand for small, power-efficient switches, Diodes Incorporated launched the AH138x and AH139x. This is a family of micropower, push-pull, unipolar Hall switches that are ideal for portable, battery-powered devices.

The two switches differ in the outputs provided. Firstly, the AH139x series has two outputs: one responds to a North pole, the other responds to a South pole. The AH138x series has a single output, which responds to a South pole.

These devices have a wide input voltage range of 1.6V to 5.5V. As a result, they can be powered directly from a battery, thus eliminating the cost and board space demands of power conversion. They only require an ultra-low 1.6μA (typical) average supply current over the full voltage range, and this drops to only 1.1µA at 1.85V. This means that power consumption is minimized, helping extend battery life.

A pull-up resistor is unnecessary as the AH138x and AH139x have an internal push-pull output structure to reduce external component count. This makes the design simpler and smaller, further saving board space.

All switches in this family are provided in compact DFN1010-4 and DFN1410-4 packages, and the AH1381, AH1382, and AH1383 versions are additionally available in SOT23 packages. They have high electrostatic (ESD) protection to improve their robustness and reliability.

Overall, the AH138x and AH139x provide small, simple, and flexible contactless switch solutions for portable, battery-powered applications.

[1] https://www.knowledge-sourcing.com/report/hall-effect-sensor-market

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