TC665 Microchip Technology Inc., TC665 Datasheet - Page 9

• Manufacturer Part Number: TC665
• Description: Smbus Pwm Fan Speed Controllers With Fan Fault Detection
• Manufacturer: Microchip Technology Inc.

4.0
The TC664/TC665 devices allow you to control, moni-
tor and communicate (via SMBus) fan speed for 2-wire
and 3-wire DC brushless fans. By pulse width modulat-
ing (PWM) the voltage across the fan, the TC664/
TC665 controls fan speed according to the system tem-
perature.The goal of temperature proportional fan
speed control is to reduce fan power consumption,
increase fan life and reduce system acoustic noise.
With the TC664/TC665 devices, fan speed can be con-
trolled by the analog input V
allowing for high system flexibility.
The TC664/TC665 devices also measure and monitor
fan revolutions per minute (RPM). A fan’s speed (RPM)
is a measure of its health. As a fan’s bearings wear out,
the fan slows down and eventually stops (locked rotor).
By monitoring the fan’s RPM level, the TC664/TC665
devices can detect open, shorted, unconnected and
locked rotor fan conditions. The fan speed threshold
FIGURE 4-1:
2002 Microchip Technology Inc.
DEVICE OPERATION
Microcontroller
34.8 k
14.7 k
PICmicro
Note: Refer to Table 7-1 for R
R
R
1
2
R
+5 V
20 k
SCLK
®
Typical Application Circuit.
20 k
C
R
+5 V
+5 V
F
SDA
IN
C
0.01 µF
or the SMBus interface,
1.0 µF
1
NTC Thermistor
100 k @ 25°C
1
2
3
4
V
C
SCLK
SDA
IN
F
SENSE
TC664
TC665
value.
GND
V
DD
10
5
C
1 µF
SENSE
2
can be set to provide a predictive fan failure feature.
This feature can be used to give a system warning and,
in many cases, help to avoid a system thermal shut-
down condition. The fan RPM data and threshold reg-
isters are available over the SMBus interface which
allows for complete system control.
The TC664/TC665 devices are identical in every
aspect except for how they indicate an over-tempera-
ture condition. When V
cal), both devices will set OTF (bit 5<X>) in the Status
Register to a '1'. The TC665 will additionally pull the
FAULT output low during
condition.
FAULT
V
OUT
NC
+5 V
9
8
7
6
C
0.1 µF
SENSE
715
R
R
20 k
ISO
TC664/TC665
FAULT
+12 V
IN
FAN
voltage exceeds 2.6 V (typi-
R
SENSE
an over-temperature
DS21737A-page 9