Microchip Technology TC670ECH Datasheet

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, 90µA(typ.)

•V

Range 3.0V to 5.5V

DD

• Availableina6-PinSOT-23Package

Applications

• Protection for Linear Controlled Fans

• Power Supplies

• IndustrialEquipment

• PCs and Notebooks

• Data Storage

• Data Communications Equipment

• Instrumentation

Device Selection Table

Part Number Package Temp. Range

TC670ECH 6-Pin SOT-23 -40°C to +85°C

Package Type

SOT-23A-6

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. W hen the fan
speed falls below a user specified level, the TC670
asserts an ALERT

signal. With this design, a critical
minimum fan speed i s determined by the user. The f an
alert level is then set with a resistor divider on the
THRESHOLD pin (Pin 1) of t he TC670. When the
minimum f an speed is r eached, the ALERT

pin (Pin 5)
changes from a digital HIGH t o LOW. This failure
detection works with all linear controlled 2-wire fans.
The TC670eliminatestheneedfor3-wire fan solutions.

A

CLEAR option can be used to reset the ALERT signal,

allowing the flexibility of connecting the ALERT

output
of the TC670 with other Al ert/FAULT interrupts 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 SOT23-6 pin package and
consumes 90µA (typ) during operation. The space
saving package and low power consumption make this
device an ideal choice for systems r equiring fan speed
monitoring.

Typical Application Circuit

+5V

THRESHOLD

CLEAR



2002 Microchip TechnologyInc. DS21688B-page 1

1

GND

25

3

TC670ECH

6

4

SENSE

ALERT

V

DD

From
Microcontroller

0.1µF

R

3

R

2

4

V

DD

CLEAR

3

1

THRESHOLD

GND

2

ALERT

SENSE

ALERT
LED

R

4

+12V

5

C

SENSE

6

R

SENSE

DC

FANDCFAN

TC670

1.0 ELECTRICAL
CHARACTERISTICS

Stresses above those listed under “Absolute Maximum Rat­ings”maycausepermanentdamage to the device.These are
stress ratings only and functional operation of the device at
these or any other conditions above those indicated in the

Absolute Maximum Ratings*

VDD...................................................................................6.0V

All inputs and outputs w.r.t. .....(GND − 0.3V) to (V

Difference Input voltage ...................................... IV

DD

DD

+0.3V)

-GND

operation sections of the specifications is not implied. Expo­sure to Absolute Maximum R ating conditions for extended
periodsmay affectdevice reliability.

Output Short Circuit Current ..................................continuous

Current at Input Pin ................................................... +/-2 mA

Current at Output Pin .............................................. +/-25 mA

JunctionTemperature, T

.............................................150°C

J

ESDprotectiononallpins.................................................. ≥ 4kV

Operating Temperature Range........................-40°C to +85°C

Storage Temperature Range.........................-55°C to +150°C

TC670 ELECTRICAL SPECIFICATIONS

Electrical Characteristics: Unless otherwise specified,all limits are specified at +25°C, VDD=3.0Vto5.5V,CLEAR=Low.
Boldface type specificationsapply for temperaturerangeof -40°Cto +85°C

Symbol Parameters Min Typ Max Unit Conditions

Power Supply:

V

DD

I

DD

CLEAR Input:

V

IH

V

IL

SENSE Input:

V

TH(SENSE)

R

SENSE

THRESHOLD Input:

ALERT

ALERT

V

LOW

t

DELAY

Note 1: The TC670 will operate properly over the entire power supply range of 3.0V to 5.5V. As VDDvaries from 3.0V, accuracy will degrade

Supply Voltage 3.0 — 5.5 V
Supply Current — 90 150 µA

CLEARLogicInput High Level 0.8V
CLEARLogicInput Low Level — — 0.2V

—— V

DD

DD

SENSE Input Level Threshold Voltage — 124 — mV
SENSE Input Resistance — 50 — kΩ

THRESHOLD Input Voltage Minimum — 0.0 — V
THRESHOLD Input Voltage Maximum — 2.4 — V
THRESHOLD Input Resistance — 100 — MΩ

Programmed Fan Speed AlertAccuracy

ACC

(1)

-10 — +10 % VDD=3.0V

Output:

ALERT Output Low Voltage — — 0.3 V I
ALERT OutputDelay Time — 176 — ms

based on the percentage of V

as shown in Section 3.0.

DD

V

=2.5mA

SINK

TEMPERATURE SPECIFICATIONS

Electrical Characteristics: Unless otherwise specified, all limits are specified for -40°C to +85°C and VDD=3.0Vto5.5V

Symbol Parameters Min Typ Max Unit Conditions

Temperature Ranges:

T

A

T

A

Thermal Package Resistances:

θJA ThermalResistance,6L-SOT-23 — 230 — °C/W

DS21688B-page 2

SpecifiedTemperature Range -40 — +85 °C
Operating Temperature Range -40 — +85 °C



2002 Microchip TechnologyInc.

2.0 PIN DESCRIPTIONS

ThedescriptionsofthepinsarelistedinTable2-1.

TABLE 2-1: PIN FUNCTION TABLE

TC670

Pin No.

(6-Pin SOT-23)

1 THRESHOLD Analog Input used to set Fan ALERT

2 GND Ground Terminal.
3 CLEAR DigitalInput. Active High. The ALERT

4V
5ALERT

6 SENSE Analog Input. Current spikes are detected at this pin as the fan excitation signal

Symbol Description

Threshold Voltage.Input range = 0.0V to

2.4V.

Output is cleared when a high level signal is

applied to this input.

DD Power Supply Input, 3.0V to 5. 5V.

Digital (Open Drain) Output, active low. This pin goes low to indicate an alert
condition when the f an speed at the SENSE pin reaches the alert threshold
applied on the THRESHOLD pin.

transitionsfrom high to low and low to high.



2002 Microchip TechnologyInc. DS21688B-page 3

TC670

3.0 TYPICAL PERFORMANCE CHARACTERISTICS

Note: The graphs and tables provided following this note are a statisticalsummary based on a limited number of

samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range ( e.g., outside specified power supply range) and therefore outside the warranted range.

Supply Current IDD vs. Supply Voltage (VDD)
vs. Temperature (T

115

110

105

100

95

90

85

SUPPLY CURRENT (µA)

80

75

70

2.7

3.3

3.0

3.6

THRESHOLD Voltage vs. Fan Speed vs. Supply Voltage (VDD)

15000
14000
13000
12000
11000
10000

9000
8000
7000
6000
5000
4000

FAN SPEED (RPM)

3000
2000
1000

0

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50

= 2.7V

V

DD

4.2

3.9

SUPPLY VOLTAGE (V)

V

= 3.0V

DD

THRESHOLD VOLTAGE (V)

)

A

4.8

5.1

VDD = 3.6V

4.5

= 3.3V

V

DD

ALERT

vs. Fan Speed vs. Temperature

ACC

13000

)

12000
11000
10000

9000
8000
7000

TA = -40˚C

= +25˚C

T

A

T

A

= +90˚C

6000

FAN SPEED (RPM

5000
4000
3000

VDD = 3.0V

-10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0

5.4

6.0

5.7

ALERT

Alert Output Delay (T

Power Supply Voltage (VDD)

177

176

175

V

= 5.5V

DD

= 5.0V

V

DD

174

173

172

171

170

169

ALERT OUTPUT DELAY TIME (ms)

168

2.5 3.0 3.5 4.0 4.5 5.0

POWER SUPPLY VOLTAGE (V

ACC

(%)

DELAY

) vs.

DD

)

ALERT V

160

140

120

100

80

LOW (mV)

60

OUT

40

20

ALERT V

0

0.5 1 1.5 2 2.5 3 3.5 4 4.5

DS21688B-page 4

LOW

V

VDD = 2.7V

ALERT I

vs. ALERT I

V

DD

= 3.0V

DD

(mA)

SINK

= 3.6V

V

SINK

V

DD

DD

= 5.0V

= 5.5V

CLEAR Pin HIGH to ALERT pin HIGH

Timing Diagram



2002 Microchip TechnologyInc.