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TC648VOA713

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P28
2001-2012 Microchip Technology Inc. DS21448D-page 7
TC648
FIGURE 3-1: TC648 Nominal Operation.
4.0 SYSTEM BEHAVIOR
The flowcharts describing the TC648’s behavioral
algorithms are shown in Figure 4-1. They can be
summarized as follows:
4.1 Power-Up
(1) Assuming the device is not being held in shut-
down or auto-shutdown mode (V
IN
> V
AS
)..........
(2) Turn V
OUT
output on for 32 cycles of the PWM
clock. This ensures that the fan will start from a
dead stop.
(3) Branch to Normal Operation.
(4) End.
4.2 Normal Operation
Normal Operation is an endless loop which may only
be exited by entering shutdown or auto-shutdown
mode. The loop can be thought of as executing at the
frequency of the oscillator and PWM.
(1) Drive V
OUT
to a duty cycle proportional to V
IN
on a
cycle by cycle basis.
(2) If an over-temperature fault occurs, (V
IN
> V
OTF
),
activate OTF
; release OTF when V
IN
< V
OTF
.
(3) Is the TC648 in shutdown or auto-shutdown
mode?
If so.....
a. V
OUT
duty cycle goes to zero.
b. OTF
is disabled.
c. Exit the loop and wait for V
IN
> (V
AS
+ V
HAS
),
then execute Power-up sequence.
(4) End.
2.6V
V
AS
+
V
HAS
V
IN
t
RESET
V
REL
V
SHDN
V
AS
1.2V
TC646
Status
Normal
Operation
Auto-Shutdown
Mode
Normal
Operation
Shut-
Down
Normal
Operation
GND
Time
TEMP.
HI
LO
TC648
DS21448D-page 8 2001-2012 Microchip Technology Inc.
FIGURE 4-1: TC648 Behavioral Algorithm Flowcharts.
V
OUT
= 0
V
IN
> V
OTF
?
Auto-
Shutdown
V
OUT
= 0
No
Yes
Normal
Operation
V
IN
< V
AS
?
No
Yes
V
OUT
Duty
Cycle Prop.
to V
IN
OTF = 0
OTF = 1
No
YES
Fire Start-up
Timer
Normal
Operation
V
AS
≈ 0V
V
IN
< V
AS
?
Auto-
Shutdown
V
OUT
= 0
Yes
No
Yes
Power-Up
Minimum
Speed Mode
Power-on
Reset
OTF = 1
V
IN
>
(V
AS
+ V
HAS
)
No
Power-Up
V
IN
≈ 0V ?
V
IN
> 1.25V ?
V
IN
> 1.25V
No
No
Yes
Yes
No
Yes
Yes
Minimum
Speed Mode
No
V
OUT
= 0
OTF = 0
V
IN
> V
OTF
?
V
OUT
Duty Cycle Proportional to V
IN
OTF = 1
2001-2012 Microchip Technology Inc. DS21448D-page 9
TC648
5.0 TYPICAL APPLICATIONS
Designing with the TC648 involves the following:
(1) The temperature sensor network must be
configured to deliver 1.25V to 2.65V on V
IN
for 0%
to 100% of the temperature range to be regulated.
(2) The auto-shutdown temperature must be set with
a voltage divider on V
AS
(if used).
(3) The output drive transistor and base resistor must
be selected.
(4) If reset/shutdown capability is desired, the drive
requirements of the external signal or circuit must
be considered.
The TC642 demonstration and prototyping board
(TC642DEMO) and the TC642 Evaluation Kit
(TC642EV) provide working examples of TC648 cir-
cuits and prototyping aids. The TC642DEMO is a
printed circuit board optimized for small size and ease
of inclusion into system prototypes. The TC642EV is a
larger board intended for benchtop development and
analysis. At the very least, anyone contemplating a
design using the TC648 should consult the documenta-
tion for both the TC642EV (DS21403) and
TC642DEMO (DS21401). Figure 5-1 shows the base
schematic for the TC642DEMO.
An Excel-based spreadsheet is also available for
designing the thermistor network for the TC64X fan
controllers. This file (TC64X Therm) is available for
downloading from the Microchip website at
www.microchip.com.
FIGURE 5-1: Typical Application Circuit.
OTF
NC
NTC
R
1
R
2
R
3
R
4
GND
*See cautions regarding latch-up considerations in Section 5.0, "Typical Applications".
**O
p
tional. See Section 5.0, "T
yp
ical A
pp
lications", for details.
NOTES:
Over-
Temperature
Interrupt
Shutdown**
Q
1
+12V
+5V*
V
DD
V
IN
V
AS
V
OUT
R
BASE
C
F
1 µF
C
F
TC648
Fan
C
B
0.01 µF
C
B
0.01 µF
C
B
1 µF
+5V
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P28

TC648VOA713

Mfr. #:
Buy TC648VOA713
Manufacturer:
Microchip Technology
Description:
Motor / Motion / Ignition Controllers & Drivers Shtdn & Over-T Alert
Lifecycle:
New from this manufacturer.
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