Datasheet

TC642B/TC647B
DS21756C-page 10  2002-2013 Microchip Technology Inc.
3.0 PIN FUNCTIONS
The description of the pins are given in Table 3-1.
TABLE 3-1: PIN FUNCTION TABLE
3.1 Analog Input (V
IN
)
The thermistor network (or other temperature sensor)
connects to V
IN
. A voltage range of 1.20V to 2.60V (typ-
ical) on this pin drives an active duty cycle of 0% to
100% on the V
OUT
pin.
3.2 Analog Output (C
F
)
C
F
is the positive terminal for the PWM ramp generator
timing capacitor. The recommended value for the C
F
capacitor is 1.0 µF for 30 Hz PWM operation.
3.3 Analog Input (V
MIN
)
An external resistor divider connected to V
MIN
sets the
minimum fan speed by fixing the minimum PWM duty
cycle (1.20V to 2.60V = 0% to 100%, typical). The
TC642B and TC647B devices enter shutdown mode
when 0  V
MIN
 V
SHDN
. During shutdown, the FAULT
output is inactive and supply current falls to 30 µA
(typical).
3.4 Analog Input (SENSE)
Pulses are detected at SENSE as fan rotation chops
the current through a sense resistor. The absence of
pulses indicates a fan fault condition.
3.5 Digital (Open-Drain) Output
(FAULT
)
The FAULT line goes low to indicate a fault condition.
When FAULT
goes low due to a fan fault, 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 TC642B device, the FAULT
output will also be asserted when the V
IN
voltage
reaches the V
OTF
treshold of 2.62V (typical). This gives
an over-temperature/100% fan speed indication
.
3.6 Digital Output (V
OUT
)
V
OUT
is an active-high complimentary output and
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
OUT
output is continuously on.
3.7 Power Supply Input (V
DD
)
The V
DD
pin with respect to GND provides power to the
device. This bias supply voltage may be independent of
the fan power supply.
Pin Name Function
1V
IN
Analog Input
2C
F
Analog Output
3V
MIN
Analog Input
4 GND Ground
5 SENSE Analog Input
6FAULT
Digital (Open-Drain) Output
7V
OUT
Digital Output
8V
DD
Power Supply Input