The AH277A is an integrated Hall sensor with an output driver designed for brushless DC motor electronic interchange. Packaged in TO-94 (SIP-4L), the device includes an on-chip Hall sensor for magnetic sensing, an amplifier that amplifies Hall voltage, a Schmidt flip-flop that provides switching hysteresis TO suppress noise, a temperature compensation circuit that compensates Hall sensitivity temperature drift, and two complementary open-collector drivers to reduce large-load currents.
Functional Block Diagram
It also includes an internal bandgap regulator to provide a bias voltage to the internal circuit. Place the device in a variable magnetic field. If the flux density is greater than the threshold BOp, pin DO will be lower (on) and pin DOB will be higher (off). This output state remains until the flux density reverses and drops below the BRP, which then causes the DO to become high (off) and the DOB to become low (on).
The AH277A has reverse supply voltage protection. For DC fan applications, it is sometimes necessary to test the power back connection. The internal diode only protects the chip side, not the coil side. It is recommended to add an external diode D1 to the application to block the reverse current on the coil side
Typical Application Circuit
Features
● On-Chip Hall Sensor
● 3.5V to 16V Supply Voltage
● 400mA (avg) Output Sink Current
● Reversed Supply Voltage Protection
● -20oC to 85oC Operating Temperature
● Low Profile TO 94 (SIP-4L) Package
● ESD Rating: 300V (Machine Model)
Applications
● Dual-Coil Brushless DC Motor
● Dual-Coil Brushless DC Fan
● Revolution Counting
● Speed Measurement
