Datasheet

TC642B/TC647B
DS21756C-page 16  2002-2013 Microchip Technology Inc.
FIGURE 4-9: TC642B/TC647B Behavioral Algorithm.
FAULT = Low,
V
OUT
= High
16 Pulses
Detected?
No
Yes
Power-Up
V
MIN
<V
SHDN
?
V
MIN
> V
REL
?
Fan Pulse
Detected?
Fan Pulse
Detected?
V
MIN
< V
SHDN
?
Shutdown
V
OUT
= 0
Yes
No
No
No
Yes
Yes
Power-Up
Normal
Operation
Fan Fault
Power-on
Reset
FAULT
= 1
V
MIN
> V
REL
?
No
Yes
Fire Start-up
Timer
(1 sec)
Fire Start-up
Timer
(1 sec)
Yes
Fan Fault
Clear Missing
Pulse Detector
V
OUT
Proportional to Greater
of V
IN
or V
MIN
V
IN
> V
OTF
?
M.P.D.
Expired?
No
No
No
No
No
Yes
Yes
Yes
Normal
Operation
Power-Up
Yes
No
FAULT = 0
Yes
Fire
Diagnostic
Timer
(100 msec)
Yes
No
Yes
Normal
Operation
Shutdown
V
OUT
= 0
Yes
No
No
TC642B Only
V
MIN
< V
SHDN
?
Shutdown
V
OUT
= 0
V
MIN
> V
REL
?
Fan Pulse
Detected?
Fan Pulse
Detected?
Fire Start-up
Timer
(1 sec)
Fan Pulse
Detected?
Fan Fault