Datasheet

TC646B/TC648B/TC649B
DS21755C-page 16  2002-2013 Microchip Technology Inc.
FIGURE 4-9: TC646B/TC649B Behavioral Algorithm.
Fire Start-up
Timer
(1 sec)
Fan Pulse
Detected?
Fan Pulse
Detected?
V
IN
< V
SHDN
?
V
IN
< V
AS
?
Shutdown
V
OUT
= 0
Auto-
Shutdown
V
OUT
= 0
Yes
No
No
No
No
Yes
Yes
Yes
Power-Up
Normal
Operation
Fan Fault
Power-on
Reset
FAULT
= 1
V
IN
> V
REL
?
No
V
IN
>
(V
AS
+ V
HAS
)
Yes
Yes
No
Hot Start
Fire Start-up
Timer
(1 sec)
Fire Start-up
Timer
(1 sec)
V
IN
> V
REL?
Yes
Fan Fault
Clear Missing
Pulse Detector
V
OUT
Proportional
to V
IN
V
IN
< V
SHDN
?
V
IN
< V
AS
?
V
IN
> V
OTF
?
M.P.D.
Expired?
Fan Pulse
Detected?
Shutdown
V
OUT
= 0
Auto
Shutdown
V
OUT
= 0
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Normal
Operation
Power-Up
V
IN
>
(V
AS
+ V
HAS
)
No
Yes
Hot Start
Yes
No
FAULT = 0
Yes
Fire
Diagnostic
Timer
(100 msec)
Fan Pulse
Detected?
Fan Pulse
Detected?
Yes
No
FAULT
= Low,
V
OUT
= High
16 Pulses
Detected?
No
Yes
Power-Up
V
IN
< V
SHDN
?
V
IN
> V
REL
?
Fan Fault
Yes
Normal
Operation
Shutdown
V
OUT
= 0
Yes
No
No
TC646B Only