Datasheet

TC654/TC655
DS21734B-page 8  2002-2013 Microchip Technology Inc.
3.0 PIN FUNCTIONS
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1: PIN FUNCTION TABLE
3.1 Analog Input (V
IN
)
A voltage range of 1.62 V to 2.6 V (typical) on this pin
drives an active duty-cycle of 30% to 100% on the
V
OUT
pin.
3.2 Analog Output (C
F
)
Positive terminal for the PWM ramp generator timing
capacitor. The recommended C
F
is 1 µF for 30 Hz
PWM operation.
3.3 SMBus Serial Clock Input (SCLK)
Clocks data into and out of the TC654/TC655. See
Section 5.0 for more information on the serial interface.
3.4 Serial Data (Bi-directional) (SDA)
Serial data is transferred on the SMBus in both direc-
tions using this pin. See Section 5.0 for more informa-
tion on the serial interface.
3.5 Digital (Open Drain) Output
(FAULT
)
When the fan’s RPM falls below the user-set RPM
threshold (or OTF occurs with TC655), a logic low sig-
nal is asserted.
3.6 Analog Input (SENSE2)
Fan current pulses are detected at this pin. These
pulses are counted and used in the calculation of the
fan2 RPM.
3.7 Analog Input (SENSE1)
Fan current pulses are detected at this pin. These
pulses are counted and used in the calculation of the
fan1 RPM.
3.8 Digital Output (V
OUT
)
This active high complimentary output drives the base
of an external transistor or the gate of a MOSFET.
3.9 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.
Name Function
V
IN
Analog Input
C
F
Analog Output
SCLK Serial Clock Input
SDA Serial Data In/Out (Open Drain)
GND Ground
FAULT
Digital (Open Drain) Output
SENSE2 Analog Input
SENSE1 Analog Input
V
OUT
Digital Output
V
DD
Power Supply Input