5275

The increased current sinking capability of the UGN5275K ideally suits it for building small, inexpensive brushless dc motors using a minimum number of external components.  Figure 2 shows that the only components required to commutate motor windings L1 and L2 are the Hall effect IC, flyback diodes D1 and D2, and one decoupling capacitor.  The remaining components are optional for improving motor performance.  Care should be taken to ensure that the motor winding impedances are high enough to guarantee that start-up surge currents do not exceed the maximum rating of the Hall effect IC.

In the circuit shown, diodes D1 and D2 supply a flyback path for the current of each winding to prevent reactive voltages from exceed-ing the sustained voltage rating of the Hall-effect IC output transistors.Zener diode Z1 enables the windings to switch more rapidly by allowing the output voltage to rise above the source voltage, while simultaneously clamping the extreme reactive voltages.

The maximum output voltage level will be restricted to the following: VCC - VD3 + VZ + VD1 (blocking diode D3 voltage drop).  Blocking diode D3 provides reverse input-polarity protection, and should be used only if reverse battery voltage is a possibility.  Capacitor C1 decouples the Hall-effect IC from any high dv/dt transients injected onto the VCC rail to prevent regulator latch-up within the device.  Zener diode Z2 and resistor R1 are required for operation from a VCC exceeding 14 V.

Type UGN5275K latching Hall-effect sensors are bipolar integrated circuits designed for electronic commutation of brushless dc motors. UGN5275K feature open-collector complementary power outputs that are capable of sinking up to 300 mA continuously.  Increased current ratings, complementary outputs, and sensitive switching points that are stable over temperature and time ideally suit these devices for minimum-component brushless dc motor designs.

Each sensor IC UGN5275K includes a Hall-voltage generator, an operational amplifier, a Schmitt trigger, a voltage regulator, and large-area dual npn-output transistors.  The regulator UGN5275K allows the IC to operate with supply voltages ranging from 4.5 V to 14 V.  On-chip compensation circuitry stabilizes switch point performance over temperature.  The large bipolar junction output transistors are fed by a unique driver stage, which minimizes power dissipation within the IC.  The magnetic operation of this UGN5275K is similar to that of the UGN3275K complemen-tary-output Hall-effect latch.

Output Q of the IC UGN5275K switches to the LOW state when the internal Hall generator experiences a magnetic field that exceeds the rated operate point.  Output Q switches HIGH within one µs of the Output Q change of state.  When the UGN5275K is exposed to a sufficient magnetic field of opposite polarity, Output Q returns to the HIGH state, and Output Q returns to the LOW state.

The UGN5275K is rated for operation over a temperature range of -20°C to +85°C, and is supplied in an environmentally rugged, four-pin miniature plastic SIP.  Consult the factory for alternate packaging and custom magnetic requirements.