Honeywell's Nanopower series of Magnetoresistive (MR) sensor ICs are ultra-sensitive devices designed for a wide range of applications, featuring large air gaps, low magnetic field sensitivity, and low power characteristics. These sensor ICs respond to the application of a north or south pole in the direction parallel to the sensor. They do not require the identification of magnetic poles, simplifying installation and potentially reducing system costs. These sensor ICs consume very low average current and feature push-pull outputs that do not require pull-up resistors. The sensor ICs can operate with a supply voltage as low as 1.65 V, enhancing energy efficiency. The Nanopower series offers two magnetic sensitivities to meet various application needs:

1. SM351LT: Suitable for applications requiring ultra-high magnetic sensitivity (typical operation at 7 G, maximum operation at 11 G) and extremely low current consumption (typical value of 360 nA).

2. SM353LT: Suitable for applications requiring very high magnetic sensitivity (typical operation at 14 G, maximum operation at 20 G) and extremely low current consumption (typical value of 310 nA). The Nanopower series is packaged in an ultra-compact SOT-23 surface-mount package, available in tape and reel (3,000 units per reel), for automated pick-and-place component assembly. The operating temperature ranges from -40°C to +85°C.

Compared to existing Hall-effect sensors, Honeywell's Nanopower series sensor ICs offer several unique performance advantages that translate into practical benefits, including low power consumption, reduced overall system costs, greater design flexibility, simplified installation, and minimal changes in system design.

In typical cases of 310 nA and 360 nA, the Nanopower series uses 1/16th the power of even the most efficient Hall effect devices. For many battery-powered devices, the power budget is tight, and every nanoamp counts, allowing design engineers to save on battery life or incorporate additional low-power technologies into their applications.

In addition to providing energy savings, the sensor's CMOS output circuitry eliminates the need for external pull-up resistors. The MR sensors also remove the need for discrete components used to filter electrical noise generated by helicopter circuits, which are commonly used by Hall effect devices. Eliminating these discrete components can reduce the physical footprint of the sensor assembly, making them easier to use in space-constrained applications.

As an MR device, these new sensors also exhibit much higher sensitivity than Hall effect devices. In fact, in typical cases of 7 G and 14 G, these sensors can detect magnetic fields from more than twice the distance compared to Hall sensors currently on the market, directly translating into system cost savings by allowing for the use of smaller magnets, or even magnets made from different materials in their systems. This is especially important today as the prices of rare-earth magnets are rising rapidly due to a global shortage of rare-earth supply.

The high sensitivity offered by these devices also allows for greater design flexibility. Using higher sensitivity sensors will permit larger air gaps between the magnetic target and the sensor. This is beneficial in many applications where board space is limited, or the ideal position for the sensor needs to be just a few millimeters away from the target.

Applications of SM351LT and SM353LT

Industrial

• Mobile devices (e.g., handheld computing devices, scanners): The ultra-low power characteristics and small size of MR sensors make them suitable for battery-operated consumer electronics applications.
  

• Water, electricity, and gas utility meters.
  

• Door and window position detection for security sensors: Detecting whether a door or window is open or closed and sending a signal to a wireless module that transmits the signal to a central control unit for processing.
  

• Industrial smoke detectors: In this case, the sensor is used as a test switch to ensure that the backup batteries of building smoke detectors are operational. High sensitivity is required to ensure that personnel can test the system without error.
  

Medical

• Fitness equipment.
  
  
• Infusion pumps.
  
  
• Drawer position sensing (e.g., medical cabinets).
  
  
• Hospital beds.
  

White Goods

• Detection of lids, doors, and drawer positions.
  
  
• Fluid flow detection.
  
  
• Medium Consumer Electronics.
  
  
• Battery-optimized position sensors.