Data Sheet
TWO PHASE HALL EFFECT LATCH WITH LOCKED PROTECTION
AH287
Operating Diagram (Note 4)
Hall Input
ON
OFF
Motor Output
CT
Clamp
Voltage
CT
Comparator
CT
Voltage
Motor lock
cleared
Motor locked
TOFF
TON
Reverts to normal operation
Motor lock detected
Note 4: The automatic restart circuit detects a motor lock condition and automatically turns off the output current.
When the lock is cleared, the IC automatically restarts and allows the motor to run. In AH287, automatic restart
is performed in the following manner. A motor lock condition is detected when the Hall signal stops switching.
The output is ON when CT pin is being charged, and OFF when CT pin is being discharged.
C *(VCL − VCP
)
T
T
ON
=
(Sec)
(Sec)
ICHG
C *(VCL − VCP
)
OFF
=
IDHG
Output ON time (TON) and OFF time (TOFF) are determined by C, the capacitance of the CT pin external
capacitor.
V
V
CL is the CT pin clamp voltage
CP is the CT pin comparator voltage
I
CHG is the CT pin charge current
IDHG is the CT pin discharge current
Figure 13. Control Timing Diagram of AH287
Oct. 2009 Rev. 1. 3
BCD Semiconductor Manufacturing Limited
10
BCDSEMI [ BCD SEMICONDUCTOR MANUFACTURING LIMITED ]
