SDC277 ic

         Speed Measurement

         Revolution Counting

         Dual coils Brush-less DC Fan

         Dual coils Brush-less DC Motor

n       APPLICATION

         Low profile 4 pin SIP package

         20 to 85 operating temperature

         Building-in protecting diode only for chip reverse power connecting

         250mA(avg) output sink current

         3.5V to 20V operating voltage

         and hysteresis settings for SDC277

         On-chip Hall sensor with two different sensitivity

n       FEATURES

 For DC fan application, sometimes need to test power revere connection condition. Internal diode only protects chip-side but not for coil-side. If necessary, add one external diode to block the reverse current from coil-side.

While the magnetic flux density(B) is larger than operate point (BOP). Do will turn on (low), and meanwhile DOB will turn off (high). Each output is latched until B is lower than release point(Brp), and then DO, DOB transfer each state.

The SDC277 are integrated Hall Sensors with output drivers, mainly designed for electronic, communication of bush-less DC Fan. This IC internally includes the regulator, protecting diode. Hall plate, amplifier, comparator, and a pair of complementary open-collector outputs (DO DOB).

n       GENERAL DESCRIPTION