3235 Datasheet

Dual-output Hall-effect Switch


Features, Applications

Type UGN3235K Hall-effect sensors are bipolar integrated circuits designed for commutation of brushless dc motors, and other rotary encoding applications using multi-pole ring magnets. The device features two outputs which are independently activated by magnetic fields of opposite polarity. Each sensor IC includes a Hall voltage generator, two Schmitt triggers, a voltage regulator, output transistors, and on-board reverse polarity protection. The regulator enables these devices to operate from voltages ranging between 4.5 V and 24 V. On-chip compensation circuitry stabilizes the switch points over temperature. Each open-collector output is independently operated by the proper amount and polarity of incident magnetic flux. Output 1 responds only to the positive flux from the south pole of a magnet, Output 2 to the negative flux from the north pole of a magnet. When the sensor experiences the field of a south magnetic pole greater than the maximum operate point of Output 1, that output switches to the LOW state and Output 2 is unaffected. When the incident flux falls below the minimum release point for Output 1, that output returns to the HIGH state and Output 2 remains unchanged. Output 2 independently responds in the same manner to the negative flux from the north magnetic pole of a magnet. Figure 1 shows a zone in the region 0 G, tH, where both outputs are in the HIGH or OFF state. This constitutes a delay that is independent of rate of change of the incident magnetic field and ensures that both outputs are never ON simultaneously. This is an essential feature for driving brushless dc motors with a minimum of reactive transient currents. The UGN3235K is supplied in a four-pin plastic single in-line package (SIP).

Pinning is shown viewed from branded side.

Power Supply, VCC. 25 V Reverse Battery Voltage, VRCC. -30 V Magnetic Flux Density, B. Unlimited Output OFF Voltage, VOUT. 25 V Output ON Current, IOUT. 50 mA Operating Temperature Range, TA. + 85�C Storage Temperature Range TS. to +150�C


s Reliable and Rugged Magnetic Sensing Switch s Two Outputs Independently Switched by North and South Poles s Independent Actuation of Outputs Minimizes Inductive-Load Reactive Transient s Built-in Hysteresis Minimizes Interference from Stray Fields s Operates from V s Outputs Compatible with All Logic Levels s On-Board Reverse Polarity Protection s Open-Collector, Active-Low Outputs

Characteristic Supply Voltage Output Saturation Voltage Output Leakage Current Supply Current Output Rise Time Output Fall Time Symbol VCC VOUT(SAT) IOFF ICC tr tf VCC 24 V, IOUT 20 mA VOUT 24 V, VCC 24 V VCC 24 V, Output Open VCC 20 pF VCC 20 pF Test Conditions Min. 4.5 Typ. Max. Units mA �s

Characteristic Operate Point, BOP Test Conditions to +85�C Release Point, BRP to +85�C Hysteresis, Bhys to +85�C Output & Q2 Min. Max. Units

115 Northeast Cutoff, Box 15036 Worcester, Massachusetts (508) 853-5000 Copyright 1989, 2002 Allegro MicroSystems, Inc.


Figure 1 illustrates a method of sensing the presence of either a north or south magnetic pole. Because the is an open-collector device, it is possible to directly connect (wired OR) the two outputs. This causes the output to go LOW when either a north pole or south pole of sufficient magnitude is sensed. The device connected in this manner suits many applications, ranging from doubling the resolution of a ring-magnet encoder, to zero-crossing detection.

Figure 2 shows that there is a "dead time" approximately centered around 0 G. Thus, by sensing the HIGH portion of the UGN3235K wired-OR output, the zerocrossing can be detected.

Figure 3 shows that the UGN3235K makes it possible to implement a very efficient brushless dc motor control using a minimum number of components. Referring again to Figure 1, the dead time (where both drivers are OFF) allows the motor coil field to decay sufficiently. This avoids both excessive reactive voltages and the magnetic drag resulting from the motor coils working in opposition to each other.



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