www.docs.chipfind.ru
2002 Microchip Technology Inc.
DS21449C-page 1
M
TC649
Features
Temperature Proportional Fan Speed for Acoustic
Control and Longer Fan Life
Efficient PWM Fan Drive
3.0V to 5.5V Supply Range:
- Fan Voltage Independent of TC649
Supply Voltage
- Supports any Fan Voltage
FanSenseTM Fault Detection Circuits Protect
Against Fan Failure and Aid System Testing
Automatic Shutdown Mode for "Green" Systems
Supports Low Cost NTC/PTC Thermistors
Space Saving 8-Pin MSOP Package
Applications
Power Supplies
Computers
File Servers
Portable Computers
Telecom Equipment
UPSs, Power Amps
General Purpose Fan Speed Control
Available Tools
Fan Controller Demonstration Board (TC642DEMO)
Fan Controller Evaluation Kit (TC642EV)
Package Types
General Description
The TC649 is a switch mode, fan speed controller for
use with brushless DC fans. Temperature proportional
speed control is accomplished using pulse width mod-
ulation (PWM). A thermistor (or other voltage output
temperature sensor) connected to the V
IN
input fur-
nishes the required control voltage of 1.25V to 2.65V
(typical) for 0% to 100% PWM duty cycle. The TC649
automatically suspends fan operation when measured
temperature (V
IN
) is below a user programmed
minimum setting (V
AS
). An integrated Start-up Timer
ensures reliable motor start-up at turn-on, coming out
of shutdown mode, auto-shutdown mode or following a
transient fault.
In normal fan operation, a pulse train is present at
SENSE (Pin 5). The TC649 features Microchip
Technology's proprietary FanSense
TM
technology for
increasing system reliability. A missing pulse detector
monitors this pin during fan operation. A stalled, open
or unconnected fan causes the TC649 to trigger its
Start-up Timer once. If the fault persists, the FAULT
output goes low, and the device is latched in its shut-
down mode. See Section 5.0, "Typical Applications",
for more information and system design guidelines.
The TC649 is available in the 8-pin PDIP, SOIC and
MSOP packages and is available in the industrial and
extended commercial temperature ranges.
SOIC/PDIP/MSOP
1
8
2
7
3
6
4
5
GND
C
F
V
IN
V
AS
FAULT
SENSE
V
DD
V
OUT
TC649
PWM Fan Speed Controller with Auto-Shutdown
and FanSenseTM Technology
TC649
DS21449C-page 2
2002 Microchip Technology Inc.
Functional Block Diagram
FAULT
SHDN
SENSE
PWM
GND
70mV (typ.)
10k
V
AS
V
SHDN
V
IN
C
F
V
DD
V
OUT
TC649
Control
Logic
+
+
+
+
3 x T
PWM
Timer
Start-up
Timer
Clock
Generator
Missing
Pulse
Detect
2002 Microchip Technology Inc.
DS21449C-page 3
TC649
1.0
ELECTRICAL
CHARACTERISTICS
Absolute Maximum Ratings*
Supply Voltage ......................................................... 6V
Input Voltage, Any Pin.... (GND 0.3V) to (V
DD
+0.3V)
Package Thermal Resistance:
PDIP (R
JA
) ............................................125C/W
SOIC (R
JA
) ............................................155C/W
MSOP (R
JA
) .......................................... 200C/W
Specified Temperature Range ........... -40C to +125C
Storage Temperature Range.............. -65C to +150C
*Stresses above those listed under "Absolute Maximum Rat-
ings" may cause permanent damage to the device. These are
stress ratings only and functional operation of the device at
these or any other conditions above those indicated in the
operation sections of the specifications is not implied. Expo-
sure to absolute maximum rating conditions for extended peri-
ods may affect device reliability.
DC ELECTRICAL SPECIFICATIONS
Electrical Characteristics: Unless otherwise specified, T
MIN
T
A
T
MAX
, V
DD
= 3.0V to 5.5V.
Symbol
Parameter
Min
Typ
Max
Units
Test Conditions
V
DD
Supply Voltage
3.0
--
5.5
V
I
DD
Supply Current, Operating
--
0.5
1.0
mA
Pins 6, 7 Open,
C
F
= 1 F, V
IN
= V
C(MAX)
I
DD(SHDN)
Supply Current, Shutdown/
Auto-shutdown Mode
--
25
--
A
Pins 6, 7 Open; Note 1
C
F
=1 F, V
IN
= 0.35V
I
IN
V
IN
,
V
AS
Input Leakage
-1.0
--
+1.0
A
V
OUT
Output
t
R
V
OUT
Rise Time
--
--
50
sec I
OH
= 5 mA, Note 1
t
F
V
OUT
Fall Time
--
--
50
sec I
OL
= 1 mA, Note 1
t
SHDN
Pulse Width (On V
IN
) to Clear Fault
Mode
30
--
--
sec V
SHDN
, V
HYST
Specifications, Note 1
I
OL
Sink Current at V
OUT
Output
1.0
--
--
mA
V
OL
= 10% of V
DD
I
OH
Source Current at V
OUT
Output
5.0
--
--
mA
V
OH
= 80% of V
DD
SENSE Input
V
TH(SENSE)
SENSE Input threshold Voltage with
Respect to GND
50
70
90
mV
Note 1
FAULT Output
V
OL
Output Low Voltage
--
--
0.3
V
I
OL
= 2.5 mA
t
MP
Missing Pulse Detector Timer
--
32/F
--
Sec
C
F
= 1.0 F
t
START
Start-up Timer
--
32/F
--
Sec
C
F
= 1.0 F
t
DIAG
Diagnostic Timer
--
3/F
--
Sec
C
F
= 1.0 F
V
IN
, V
AS
Inputs
V
C(MAX)
Voltage at V
IN
for 100% Duty Cycle
2.5
2.65
2.8
V
V
C(SPAN)
V
C(MAX)
- V
C(MIN)
1.3
1.4
1.5
V
V
AS
Auto-shutdown Threshold
V
C(MAX) -
V
C(SPAN)
--
V
C(MAX)
V
V
SHDN
Voltage applied to V
IN
to Release
Reset/Shutdown
--
--
V
DD
x 0.13
V
V
REL
Voltage applied to V
IN
to Release
Reset Mode
V
DD
x 0.19
--
--
V
V
DD
= 5V,
See Figure 5-11
V
HYST
Hysteresis on V
SHDN,
V
REL
--
0.01 x V
DD
--
V
V
HAS
Hysteresis on Auto-shutdown
Comparator
--
70
--
mV
Pulse Width Modulator
F
OSC
PWM Frequency
26
30
34
Hz
C
F
= 1.0 F
Note 1: Ensured by design, not tested.
TC649
DS21449C-page 4
2002 Microchip Technology Inc.
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
PIN FUNCTION TABLE
2.1
Analog Input (V
IN
)
The thermistor network (or other temperature sensor)
connects to the V
IN
input. A voltage range of 1.25V to
2.65V (typical) on this pin drives an active duty cycle of
0% to 100% on the V
OUT
pin. The TC649 enters shut-
down mode when V
IN
V
SHDN.
During shutdown, the
FAULT output is inactive, and supply current falls to
25 A (typical). The TC649 exits shutdown mode when
V
IN
V
REL
.
See Section 5.0, "Typical Applications", for
details.
2.2
Analog Output (C
F
)
C
F
is the positive terminal for the PWM ramp generator
timing capacitor. The recommended C
F
is 1 F for
30 Hz PWM operation.
2.3
Analog Input (V
AS
)
An external resistor divider connected to the V
AS
input
sets the auto-shutdown threshold. Auto-shutdown
occurs when V
IN
V
AS
. The fan is automatically
restarted when V
IN
(V
AS
+ V
HAS
). See Section 5.0,
"Typical Applications", for more details.
2.4
Ground (GND)
GND denotes the ground terminal.
2.5
Analog Input (SENSE)
Pulses are detected at the SENSE pin as fan rotation
chops the current through a sense resistor (R
SENSE
).
The absence of pulses indicates a fault. See
Section 5.0, "Typical Applications", for more details.
2.6
Digital Output (FAULT)
The FAULT line goes low to indicate a fault condition.
When FAULT goes low due to a fan fault condition, the
device is latched in shutdown mode until deliberately
cleared or until power is cycled.
2.7
Digital Output (V
OUT
)
V
OUT
is an active high complimentary output that drives
the base of an external NPN transistor (via an appropri-
ate base resistor) or the gate of an N-channel
MOSFET. This output has asymmetrical drive (see
Section 1.0, "Electrical Characteristics").
2.8
Power Supply Input (V
DD
)
V
DD
may be independent of the fan's power supply
(see Section 1.0, "Electrical Characteristics").
Pin No.
Symbol
Descriptiion
1
V
IN
Analog Input
2
C
F
Analog Output
3
V
AS
Analog Input
4
GND
Ground Terminal
5
SENSE
Analog Input
6
FAULT
Digital (Open Collector) Output
7
V
OUT
Digital Output
8
V
DD
Power Supply Input
2002 Microchip Technology Inc.
DS21449C-page 5
TC649
3.0
DETAILED DESCRIPTION
3.1
PWM
The PWM circuit consists of a ramp generator and
threshold detector. The frequency of the PWM is
determined by the value of the capacitor connected to
the C
F
input. A frequency of 30 Hz is recommended for
most applications (C
F
= 1 F). The PWM is also the
time base for the Start-up Timer (see Section 3.3,
"Start-up Timer"). The PWM voltage control range is
1.25V to 2.65V (typical) for 0% to 100% output duty
cycle.
3.2
V
OUT
Output
The V
OUT
pin is designed to drive a low cost transistor
or MOSFET as the low side power switching element in
the system. Various examples of driver circuits will be
shown throughout the datasheet. This output has
asymmetric complementary drive and is optimized for
driving NPN transistors or N-channel MOSFETs. Since
the system relies on PWM rather than linear control,
the power dissipation in the power switch is kept to a
minimum. Generally, very small devices (TO-92 or SOT
packages) will suffice.
3.3
Start-Up Timer
To ensure reliable fan start-up, the Start-up Timer turns
the V
OUT
output on for 32 cycles of the PWM whenever
the fan is started from the off state. This occurs at
power-up and when coming out of shutdown or auto-
shutdown mode. If the PWM frequency is 30 Hz (C
F
=
1 F) the resulting start-up time will be approximately
one second. If a fan fault is detected (see Section 3.5,
FAULT Output), the Diagnostic Timer is triggered once,
followed by the Start-up Timer. If the fault persists, the
device is shut down (see Section 3.5, FAULT Output).
3.4
SENSE Input
(FanSenseTM Technology)
The SENSE input (Pin 5) is connected to a low value
current sensing resistor in the ground return leg of the
fan circuit. During normal fan operation, commutation
occurs as each pole of the fan is energized. This
causes brief interruptions in the fan current, seen as
pulses across the sense resistor. If the device is not in
shutdown or auto-shutdown mode, and pulses are not
appearing at the SENSE input, a fault exists.
The short, rapid change in fan current (high dl/dt)
causes a corresponding dV/dt across the sense
resistor, R
SENSE
. The waveform on R
SENSE
is
differentiated and converted to a logic-level pulse-train
by C
SENSE
and the internal signal processing circuitry.
The presence and frequency of this pulse-train is a
direct indication of fan operation. See Section 5.0,
"Typical Applications", for more details.
3.5
FAULT Output
Pulses appearing at SENSE due to the PWM turning
on are blanked, and the remaining pulses are filtered
by a missing pulse detector. If consecutive pulses are
not detected for thirty-two PWM cycles (
1 Sec if
C
F
= 1 F), the Diagnostic Timer is activated, and
V
OUT
is driven high continuously for three PWM cycles
(
100 msec if C
F
= 1 F). If a pulse is not detected
within this window, the Start-up Timer is triggered (see
Section 3.3, "Start-up Timer"). This should clear a tran-
sient fault condition. If the missing pulse detector times
out again, the PWM is stopped and FAULT goes low.
When FAULT is activated due to this condition, the
device is latched in shutdown mode and will remain off
indefinitely. The TC649 is thus prevented from
attempting to drive a fan under catastrophic fault
conditions.
One of two things will restore operation: Cycling power
off and then on again; or pulling V
IN
below V
SHDN
and
releasing it to a level above V
REL
. When one of these
two conditions is satisfied, the normal start-up cycle is
triggered and operation will resume, provided the fault
has been cleared.
3.6
Auto-Shutdown Mode
If the voltage on V
IN
becomes less than the voltage on
V
AS
, the fan is automatically shut off (auto-shutdown
mode). The TC649 exits auto-shutdown mode when
the voltage on V
IN
becomes higher than the voltage on
V
AS
by V
HAS
(the auto-shutdown hysteresis voltage,
see Figure 3-1). The Start-up Timer is triggered and
normal operation is resumed upon exiting auto-shut-
down mode. The FAULT output is unconditionally
inactive in auto-shutdown mode.
Document Outline
PDF 
ZIP