3235

DUAL-OUTPUT

HALL-EFFECT SWITCH

TRANSFER CHARACTERISTICS

Figure 1 illustrates a method of sensing the presence

of either a north or south magnetic pole. Because the

UGN3235K 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.

APPLICATIONS

Figure 2 shows that there is a “dead time” approxi-

mately centered around 0 G. Thus, by sensing the HIGH

portion of the UGN3235K wired-OR output, the zero-

crossing can be detected.

Dwg. WH-009-1

BOP1

B

RP1

BRP2

B

OP2

Q1

Q2

0

+B (SOUTH)

–B (NORTH)

ON

OFF

ON

ON

OFF

OFF

DEAD

TIME

DEAD

TIME

FIGURE 2

ZERO-CROSSING DETECTION

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.

SWITCH POINTS vs. TEMPERATURE

X

V

CC

4.5 V to 24 V

Dwg. EH-010

SIGNAL

OUTPUT

FIGURE 1

BIPOLAR DETECTOR

0

+B

0

Dwg. GH-043A

-B

VOUT(SAT)

25 V

MAX

BOP1

BRP1

V OUT(OFF)

B OP2

BRP2

MAGNETIC FLUX

0

50

100

AMBIENT TEMPERATURE IN

°C

-50

Dwg. GH-027-1

0

50

100

-50

-100

150

150

-150

-25

25

75

125