TC647(2002) View Datasheet(PDF) - Microchip Technology
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TC647 Datasheet PDF : 28 Pages
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TC647
2.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1: PIN FUNCTION TABLE
Pin No. Symbol
Description
1
VIN Analog Input
2
CF Analog Output
3
VMIN Analog Input
4
GND Ground Terminal
5
SENSE Analog Input
6
FAULT Digital (Open Collector) Output
7
VOUT Digital Output
8
VDD Power Supply Input
2.1 Analog Input (VIN)
The thermistor network (or other temperature sensor)
connects to the VIN 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 VOUT pin.
2.2 Analog Output (CF)
CF is the positive terminal for the PWM ramp generator
timing capacitor. The recommended CF is 1 µF for
30 Hz PWM operation.
2.3 Analog Input (VMIN)
An external resistor divider connected to the VMIN input
sets the minimum fan speed by fixing the minimum
PWM duty cycle (1.25V to 2.65V = 0% to 100%, typi-
cal). The TC647 enters shutdown mode when VMIN ≤
VSHDN. During shutdown, the FAULT output is inactive
and supply current falls to 25 µA (typical). The TC647
exits shutdown mode when VMIN ≥ VREL. 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. The
absence of pulses indicates a fault.
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. FAULT may be con-
nected to VMIN if a hard shutdown is desired.
2.7 Digital Output (VOUT)
VOUT 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 MOS-
FET. This output has asymmetrical drive (see
Section 1.0, “Electrical Characteristics”).
2.8 Power Supply Input (VDD)
VDD may be independent of the fan’s power supply
(see Section 1.0, “Electrical Characteristics”).
DS21447C-page 4
2002 Microchip Technology Inc.
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