TC648 Microchip, TC648 Datasheet - Page 7

• Manufacturer Part Number: TC648
• Description: Fan Speed Controller
• Manufacturer: Microchip

FIGURE 3-1:
4.0
The flowcharts describing the TC648’s behavioral
algorithms are shown in Figure 4-1. They can be
summarized as follows:
4.1
(1) Assuming the device is not being held in shut-
(2) Turn V
(3) Branch to Normal Operation.
(4) End.
2002 Microchip Technology Inc.
V
AS
down or auto-shutdown mode (V
clock. This ensures that the fan will start from a
dead stop.
V
+ V
IN
TC646
Status
V
V
SHDN
GND
HAS
SYSTEM BEHAVIOR
Power-Up
2.6V
REL
V AS
1.2V
OUT
output on for 32 cycles of the PWM
Operation
Normal
TC648 Nominal Operation.
IN
> V
Auto-Shutdown
AS
)..........
Mode
Time
4.2
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
(2) If an over-temperature fault occurs, (V
(3) Is the TC648 in shutdown or auto-shutdown
(4) End.
Operation
Normal
cycle by cycle basis.
activate OTF; release OTF when V
mode?
If so.....
a. V
b. OTF is disabled.
c. Exit the loop and wait for V
then execute Power-up sequence.
OUT
Normal Operation
OUT
duty cycle goes to zero.
t
RESET
to a duty cycle proportional to V
Down
Shut-
Operation
Normal
IN
DS21448C-page 7
TC648
> (V
IN
< V
AS
IN
OTF
+ V
> V
LO
TEMP.
HI
IN
.
OTF
HAS
on a
),
),