TC648B Microchip Technology Inc., TC648B Datasheet - Page 10

• Manufacturer Part Number: TC648B
• Description: Pwm Fan Speed Controllers With Auto-shutdown, Fan Restart And Fansense Technology For Fault Detection
• Manufacturer: Microchip Technology Inc.

TC646B/TC648B/TC649B
3.0
The descriptions of the pins are given in Table 3-1.
TABLE 3-1:
3.1
The thermistor network (or other temperature sensor)
connects to V
ical) on this pin drives an active duty cycle of 0% to
100% on the V
TC649B
0
output is inactive and supply current falls to 30 µA
(typical).
3.2
C
timing capacitor. The recommended value for the C
capacitor is 1.0 µF for 30 Hz PWM operation.
3.3
An external resistor divider connected to V
auto-shutdown threshold. Auto-shutdown occurs when
V
V
FAULT/OTF output is inactive and supply current falls
to 30 µA (typical).
3.4
Pulses are detected at SENSE as fan rotation chops
the current through a sense resistor. The absence of
pulses indicates a fan fault condition.
DS21755B-page 10
IN
IN
F
Pin
is the positive terminal for the PWM ramp generator
1
2
3
4
5
6
7
8
V
< V
> (V
IN
AS
PIN FUNCTIONS
Analog Input (V
Analog Output (C
Analog Input (V
Analog Input (SENSE)
V
AS
devices
. The fan is automatically restarted when
SHDN
FAULT/OTF
SENSE/NC
IN
+ V
Name
. A voltage range of 1.20V to 2.60V (typ-
V
GND
. During shutdown, the FAULT/OTF
V
V
V
OUT
C
OUT
AS
DD
IN
PIN FUNCTION TABLE
F
HAS
enter
pin. The TC646B, TC648B and
). During auto-shutdown, the
shutdown
Analog Input
Analog Output
Analog Input
Ground
Analog Input/No Connect. NC for TC648B.
Digital (Open-Drain) Output
OTF for TC648B
Digital Output
Power Supply Input
AS
IN
)
F
)
)
mode
AS
sets the
when
F
3.5
FAULT/OTF goes low to indicate a fault condition.
When FAULT goes low due to a fan fault (TC646B and
TC649B devices), the output will remain low until the
fan fault condition has been removed (16 pulses have
been detected at the SENSE pin in a 32/f period). For
the TC646B and TC648B devices, the FAULT/OTF out-
put will also be asserted when the V
the V
over-temperature/100% fan speed indication
3.6
V
drives the base of an external NPN transistor (via an
appropriate base resistor) or the gate of an N-channel
MOSFET. This output has asymmetrical drive. During a
fan fault condition, the V
3.7
The V
device. This bias supply voltage may be independent of
the fan power supply.
3.8
Ground terminal.
3.9
No internal connection.
OUT
Function
OTF
DD
is an active-high complimentary output that
Digital (Open-Drain) Output
( FAULT/OTF )
Digital Output (V
Power Supply Input (V
pin with respect to GND provides power to the
Ground (GND)
No Connect (NC)
threshold of 2.62V (typical). This gives an
OUT
2003 Microchip Technology Inc.
output is continuously on.
OUT
)
IN
voltage reaches
DD
)
.