TC670_03 Datasheet, PDF (1/14 Pages) Microchip Technology – Tiny Predictive Fan Failure Detector

M
TC670
Tiny Predictive Fan Failure Detector
Features
• Fan Wear-Out Detection for 2-Wire
Linear-Controlled Fans
• Replacement System for 3-Wire Fans
• Fan Alert Signal when Fan Speed is below
Programmed Threshold
• CLEAR Capability for Eliminating False Alarm
• Low Operating Current, 90 µA (typ.)
• V_DD Range 3.0V to 5.5V
• Available in a 6-Pin SOT-23 Package
Applications
• Protection for Linear-Controlled Fans
• Power Supplies
• Industrial Equipment
• PCs and Notebooks
• Data Storage
• Data Communications Equipment
• Instrumentation
Package Type
SOT-23A-6
THRESHOLD 1
GND 2
CLEAR 3
6 SENSE
5 ALERT
4 V_DD
General Description
The TC670 is an integrated fan speed sensor that
predicts and/or detects fan failure, preventing thermal
damage to systems with cooling fans. When the fan
speed falls below a user-specified level, the TC670
asserts an ALERT signal. With this design, a critical
minimum fan speed is determined by the user. The fan
alert level is then set with a resistor divider on the
THRESHOLD pin (Pin 1) of the TC670. When the
minimum fan speed is reached, the ALERT pin (Pin 5)
changes from a digital high to low. This failure detection
works with all linear-controlled 2-wire fans. The TC670
eliminates the need for 3-wire fan solutions.
A CLEAR option can be used to reset the ALERT sig-
nal, allowing the flexibility of connecting the ALERT
output of the TC670 with other ALERT/FAULT inter-
rupts in the system. This feature can be implemented
so that false fan fault conditions do not initiate system
shutdown.
The TC670 is specified to operate over the full
industrial temperature range of -40°C to +85°C. The
TC670 is offered in a 6-pin SOT-23 pin package and
consumes 90 µA (typ.) during operation. The space-
saving package and low power consumption make this
device an ideal choice for systems requiring fan speed
monitoring.
Typical Application Circuit
+5V
4 _VDD
ALERT
LED
0.1 µF
R₄
3 ^CLEAR _{ALERT 5}
+12V
From
R₃
Microcontroller
DC
1
THRESHOLD
SENSE
6
C_SENSE ^FFAANN
R₂
GND
R_SENSE
2
 2003 Microchip Technology Inc.
DS21688C-page 1