Diodes ZXBM2004 - Manual (Page 7)

ZXBM2004
TWO PHASE VARIABLE SPEED
MOTOR CONTROL PRE-DRIVER
ZXBM2004
Document number: DS33433 Rev. 5 - 2
7 of 19
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February 2012
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UC
T
Functional Description (cont.)
C
LCK
- Locked Rotor Timing Capacitor
Should the fan stop rotating for any reason, i.e. an obstruction in the fan blade or a seized bearing, then the device will enter
a Rotor Locked condition. In this condition after a predetermined time (T
LOCK
) the RD pin will go high and the Phase outputs
will be disabled. After a further delay (T
OFF
) the controller will re-enable the Phase drive for a defined period (T
ON
) in an
attempt to re-start the fan. This cycle of (T
OFF
) and (T
ON
) will be repeated indefinitely or until the fan re-starts.
GND – Supply Return
This is the device supply ground return pin and will generally be the most negative supply pin to the fan.
RD - Rotor Lock Detect Output
This pin is the Locked Rotor status output as referred to in the C
LCK
timing section above. It is high when the rotor is stopped
and low when it is running.
This is an open collector drive giving an active pull down with the high level being provided by an external pull up resistor.
FR and RD Timing Diagram
T Lock T Off
T On
Hall
C LCK
FG
RD
V THH
V THL