TC646B View Datasheet(PDF) - Microchip Technology
Part Name
Description
Manufacturer
TC646B
Microchip Technology
TC646B Datasheet PDF : 36 Pages
| |||
TC646B/TC648B/TC649B
3.0 PIN FUNCTIONS
The descriptions of the pins are given in Table 3-1.
TABLE 3-1: PIN FUNCTION TABLE
Pin
Name
Function
1
VIN
Analog Input
2
CF
Analog Output
3
VAS
Analog Input
4
GND
Ground
5
SENSE/NC Analog Input/No Connect. NC for TC648B.
6
FAULT/OTF Digital (Open-Drain) Output
OTF for TC648B
7
VOUT
Digital Output
8
VDD
Power Supply Input
3.1 Analog Input (VIN)
The thermistor network (or other temperature sensor)
connects to VIN. 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 VOUT pin. The TC646B, TC648B and
TC649B devices enter shutdown mode when
0 ≤ VIN ≤ VSHDN. During shutdown, the FAULT/OTF
output is inactive and supply current falls to 30 µA
(typical).
3.2 Analog Output (CF)
CF is the positive terminal for the PWM ramp generator
timing capacitor. The recommended value for the CF
capacitor is 1.0 µF for 30 Hz PWM operation.
3.3 Analog Input (VAS)
An external resistor divider connected to VAS sets the
auto-shutdown threshold. Auto-shutdown occurs when
VIN < VAS. The fan is automatically restarted when
VIN > (VAS + VHAS). During auto-shutdown, the
FAULT/OTF output is inactive and supply current falls
to 30 µA (typical).
3.5 Digital (Open-Drain) Output
(FAULT/OTF)
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 VIN voltage reaches
the VOTF threshold of 2.62V (typical). This gives an
over-temperature/100% fan speed indication.
3.6 Digital Output (VOUT)
VOUT is an active-high complimentary output that
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 VOUT output is continuously on.
3.7 Power Supply Input (VDD)
The VDD pin with respect to GND provides power to the
device. This bias supply voltage may be independent of
the fan power supply.
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.
3.8 Ground (GND)
Ground terminal.
3.9 No Connect (NC)
No internal connection.
DS21755B-page 10
2003 Microchip Technology Inc.
Share Link: