Datasheet

 2002-2012 Microchip Technology Inc. DS21446D-page 9
TC646
FIGURE 4-1: TC646 Behavioral Algorithm Flowchart.
Auto-Shutdown
FAULT = 1
V
OUT
= 0
Cycling
Power
Yes
Yes
No
No
No
No
Yes
Power-Up
V
IN
> V
REL
?
Fan Pulse
Detected?
V
IN
< V
SHDN
?
V
IN
< V
AS
?
Shutdown
V
OUT
= 0
Auto-
Shutdown
V
OUT = 0
Yes
No
No
No
Yes
Yes
Power-Up
Normal
Operation
YES
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)
Fan Pulse
Detected?
No
Yes
Fan Fault
Fire Start-up
Timer
(1 SEC)
V
IN
> V
REL
Yes
FAULT = 0,
V
OUT
= 0
V
IN
< V
SHDN
?
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
(100msec)
Fan Pulse
Detected?
Fire Start-up
Timer
(1 sec)
Fan Fault
Fan Pulse
Detected?
Yes
No
V
IN
> (V
AS
+ V
HAS
)?