19-2225; Rev 1; 5/06
Remote-Junction Temperature-Controlled
Fan-Speed Regulator with SMBus Interface
MAX6660
General Description
The MAX6660 is a remote temperature sensor and fan-
speed regulator that provides a complete fan-control
solution. The remote temperature sensor is typically a
common-collector PNP, such as a substrate PNP of a
microprocessor, or a diode-connected transistor, typi-
cally a low-cost, easily mounted 2N3904 NPN type or
2N3906 PNP type.
The device also incorporates a closed-loop fan con-
troller that regulates fan speed with tachometer feed-
back. The MAX6660 compares temperature data to a
fan threshold temperature and gain setting, both pro-
grammed over the SMBus™ by the user. The result is
automatic fan control that is proportional to the remote-
junction temperature. The temperature feedback loop
can be broken at any time for system control over the
speed of the fan.
Fan speed is voltage controlled as opposed to PWM
controlled, greatly reducing acoustic noise and maxi-
mizing fan reliability. An on-chip power device drives
fans rated up to 250mA.
Temperature data is updated every 0.25s and is read-
able at any time over the SMBus interface. The
MAX6660 is accurate to 1°C (max) when the remote
junction is between +60°C to +100°C. Data is formatted
as a 10-bit + sign word with 0.125°C resolution.
The MAX6660 is specified for -40°C to +125°C and is
available in a 16-pin QSOP package.
Features
♦
Integrated Thermal Sensing and Fan-Regulation
Solution
♦
Programmable Fan Threshold Temperature
♦
Programmable Temperature Range for Full-Scale
Fan Speed
♦
Accurate Closed-Loop Fan-Speed Regulation
♦
On-Chip Power Device Drives Fans Rated
Up to 250mA
♦
Programmable Under/Overtemperature Alarms
♦
SMBus 2-Wire Serial Interface with Timeout
(Cannot “Lock Up” the SMBus)
♦
Supports SMBus Alert Response
♦
ACPI Compatible, Including
OVERT
System
Shutdown Function
♦
±1°C (+60°C to +100°C) Thermal-Sensing Accuracy
♦
MAX6660EVKIT Available
Ordering Information
PART
MAX6660AEE
TEMP RANGE
-40°C to +125°C
PIN-
PACKAGE
16 QSOP
PKG
CODE
E16-5
Applications
PC
Notebooks
Telecom Systems
Industrial Control Systems
Servers
Workstations
1µF
FAN
5kΩ
Typical Operating Circuit
+3V TO +5.5V
0.1µF
50Ω
10kΩ
EACH
+12V
VFAN
TACH IN
V
CC
STBY
SMBCLK
CLOCK
FAN
MAX6660
SMBDATA
DATA
SMBus is a trademark of Intel Corp.
2200pF
DXP
ALERT
INTERUPT
TO
µP
DXN
OVERT
Pin Configuration appears at end of data sheet.
PENTIUM
TO SYSTEM
SHUTDOWN
AGND
ADD0
ADD1
PGND
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Remote-Junction Temperature-Controlled
Fan-Speed Regulator with SMBus Interface
MAX6660
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.)
V
CC
, ADD0, ADD1, SMBDATA,
SMBCLK,
ALERT, OVERT
...................................-0.3V to +6V
V
FAN
, TACH IN, FAN .............................................-0.3V to +16V
DXP, GAIN..................................................-0.3V to (V
CC
+ 0.3V)
DXN.............................................................................-0.3V to 1V
SMBDATA,
ALERT, OVERT
Current ...................-1mA to +50mA
DXN Current ......................................................................±1mA
FAN Out Current ..............................................................500mA
ESD Protection (Human Body Model)................................2000V
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)..........667mW
Operating Temperature Range ........................ -40°C to +125°C
Junction Temperature .....................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= +3V to +5.5V, V
VFAN
= +12V, T
A
= -40°C to +125°C, unless otherwise specified. Typical values are at V
CC
= +3.3V and
T
A
= +25°C.) (Note 1)
PARAMETER
ADC AND POWER SUPPLY
V
CC
Supply Voltage
V
FAN
Supply Voltage
Operating Supply Current
Shutdown Supply Current
Temperature Resolution
T
A
= +85°C,
V
CC
= +3.3V
T
RJ
= +60°C to +100°C
T
RJ
= +25°C to +125°C
T
RJ
= -40°C to +125°C
-1
-3
-5
+25
0.25
-25
V
UVLO
V
HYST
V
CC
rising
1.4
V
CC
falling
2.50
2.80
90
2.0
90
I
RJ
V
DXN
High level
Low level
80
8
100
10
0.7
120
12
2.5
+25
3.00
V
CC
V
VFAN
I
CC
I
SHDN
Fan off
Shutdown
3.0
4.5
250
3
0.125
11
+1
+3
+5
-25
%
s
%
V
mV
V
mV
µA
V
°C
T
E
5.5
13.5
500
10
V
V
µA
µA
°C
Bits
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Temperature Error (Note 2)
Internal Reference Frequency
Accuracy
Temperature Conversion Time
Conversion Rate Timing Error
Undervoltage Lockout Threshold
Undervoltage Lockout Threshold
Hysteresis
Power-On-Reset (POR)
Threshold (V
CC
)
POR Threshold Hysteresis
Remote-Junction Source Current
DXN Source Voltage
2
_______________________________________________________________________________________
Remote-Junction Temperature-Controlled
Fan-Speed Regulator with SMBus Interface
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3V to +5.5V, V
VFAN
= +12V, T
A
= -40°C to +125°C, unless otherwise specified. Typical values are at V
CC
= +3.3V and
T
A
= +25°C.) (Note 1)
PARAMETER
Tach Input Transition Level
Tach Input Hysteresis
Current-Sense Tach Threshold
Current-Sense Tach Hysteresis
Fan Output Current
Fan Output Current Limit (Note 3)
Fan Output On-Resistance
Logic Input Low Voltage
Logic Input High Voltage
Input Leakage Current
Output Low Sink Current
Input Capacitance
Output High Leakage Current
Serial Clock Frequency
Bus Free Time Between Stop
and Start Conditions
Start Condition Setup Time
Repeat Start Condition Setup
Time
Start Condition Hold Time
Stop Condition Setup Time
Clock Low Time
Clock High Time
Data Setup Time
Data Hold Time
Receive SMBCLK/SMBDATA
Rise Time
Receive SMBCLK/SMBDATA
Fall Time
SMBus Timeout
t
SU:STA
t
HD:STA
t
SU:STO
t
LOW
t
HIGH
t
SU:DAT
t
HD:DAT
t
R
t
F
t
TIMEOUT
SMBDATA and SMBCLK time low for reset
of serial interface
25
90% to 90%
10% of SMBDATA to 90% of SMBCLK
90% of SMBCLK to 10% of SMBDATA
10% to 10%
90% to 90%
90% of SMBDATA to 10% of SMBCLK
(Note 5)
f
SCL
t
BUF
R
ONF
V
IL
V
IH
I_leak
I
OL
C
in
V
OH
= 5.5V
(Note 4)
0
4.7
4.7
50
4
4
4.7
4
250
0
1
300
40
250mA load
V
CC
= +3.0V to +5.5V
V
CC
= +3.0V
V
CC
= +5.5V
V
IN
= GND or V
CC
V
OL
= 0.4V
2.2
2.6
-2
6
5
1
100
+2
SMBus INTERFACE: SMBDATA,
ALERT, STBY, OVERT
0.8
V
V
µA
mA
pF
µA
kHz
µs
µs
µs
µs
µs
µs
µs
ns
µs
µs
ns
ms
250
320
4
410
SYMBOL
V
VFAN
= 12V
V
FAN
= 12V
CONDITIONS
MIN
TYP
10.5
190
20
0.3
MAX
UNITS
V
mV
mA
mA
mA
mA
Ω
MAX6660
Junction Temperature = T
A
. This implies zero dissipation in pass transistor (no load, or fan turned off).
T
RJ
, Remote Temperature accuracy is guaranteed by design, not production tested.
Guaranteed by design. Not production tested.
The MAX6660 includes an SMBus timeout, which resets the interface whenever SMBCLK or SMBDATA has been low for
greater than 25ms. This feature can be disabled by setting bit 2 of the Fan Gain register at 16h/1Bh to a 1. When the timeout
is disabled, the minimum clock frequency is DC.
Note 5:
Note that a transition must internally provide at least a hold time in order to bridge the undefined region (300ns max) of
SMBCLK’s falling edge.
Note 1:
Note 2:
Note 3:
Note 4:
_______________________________________________________________________________________
3
Remote-Junction Temperature-Controlled
Fan-Speed Regulator with SMBus Interface
MAX6660
Typical Operating Characteristics
(V
CC
= +3.3V, T
A
= +25°C, unless otherwise noted.)
TEMPERATURE ERROR
vs. PC BOARD RESISTANCE
MAX6660 toc01
TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
MAX6660 toc02
TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
15
TEMPERATURE ERROR (°C)
10
5
0
-5
-10
-15
-20
-25
-30
V
IN
= 100mVp-p
V
IN
= 250mVp-p
V
IN
= SQUARE WAVE APPLIED TO V
CC
WITH NO 0.1µF V
CC
CAPACITOR
MAX6660 toc03
20
15
TEMPERATURE ERROR (°C)
10
5
0
-5
-10
-15
-20
-25
-30
1
10
LEAKAGE RESISTANCE (MΩ)
PATH = DXP TO V
CC
(+5V)
PATH = DXP TO GND
5
4
TEMPERATURE ERROR (°C)
3
2
1
0
-1
-2
-3
-4
-5
20
100
-50
0
50
TEMPERATURE (°C)
100
150
1
10
100 1k
10k 100k 1M 10M 100M
FREQUENCY (Hz)
TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
MAX6660 toc04
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
0
TEMPERATURE ERROR (°C)
-1
-2
-3
-4
-5
-6
-7
-8
0 10 20 30 40 50 60 70 80 90 100
DXP-DXN CAPACITANCE (nF)
MAX6660 toc05
4.0
3.5
TEMPERATURE ERROR (°C)
3.0
2.5
2.0
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
1
10
100
1k
V
IN
= 25mVp-p
V
IN
= 50mVp-p
V
IN
= 100mVp-p
V
IN
= SQUARE WAVE
AC-COUPLED TO DXN
1
10k 100k 1M 10M 100M
FREQUENCY (Hz)
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6660 toc06
AVERAGE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6660 toc07
5
STANDBY SUPPLY CURRENT (µA)
400
AVERAGE SUPPLY CURRENT (µA)
4
300
3
2
200
1
0
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
100
3.0
3.3
3.6
3.9
4.2
4.5
4.8
5.1
5.4
SUPPLY VOLTAGE (V)
4
_______________________________________________________________________________________
Remote-Junction Temperature-Controlled
Fan-Speed Regulator with SMBus Interface
Pin Description
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
NAME
VFAN
V
CC
DXP
DXN
FAN
ADD1
PGND
AGND
OVERT
ADD0
ALERT
SMBDATA
GAIN
SMBCLK
STBY
TACH IN
Fan Drive Power-Supply Input. 4.5V to 13.5V.
Supply Voltage Input. +3V to +5.5V. Bypass V
CC
to ground with a 0.1µF capacitor.
Input: Remote-Junction Anode. Place a 2200pF capacitor between DXP and DXN for noise filtering.
Input: Remote-Junction Cathode. DXN is internally biased to a diode voltage above ground.
Open-Drain Output to Fan Low Side. Connect a minimum 1µF capacitor between FAN and VFAN.
SMBus Address Select Pin. ADD0 and ADD1 are sampled upon power-up.
Power Ground
Analog Ground
Overtemperature Shutdown Output. Active-low output (programmable for active high if desired). Open drain.
SMBus Slave Address Select Pin. ADD0 and ADD1 are sampled upon power-up.
SMBus Alert (Interrupt) Output. Open-drain, active-low output.
SMBus Serial Data Input/Output. Open drain.
Gain Control. Connect an external resistor from GAIN to V
CC
to reduce the gain of the current-sense mode.
SMBus Clock Line from Controller. This line tolerates inputs up to V
CC
even if MAX6660 is not powered.
Hardware Standby Input. Drive
STBY
low to reduce supply current. Temperature and comparison
data are retained in standby mode.
Fan Tachometer Input. Tolerates voltages up to VFAN.
FUNCTION
MAX6660
Detailed Description
The MAX6660 is a remote temperature sensor and fan
controller with an SMBus interface. The MAX6660 con-
verts the temperature of a remote-junction temperature
sensor to a 10-bit + sign digital word. The remote tem-
perature sensor can be a diode-connected transistor,
such as a 2N3906, or the type normally found on the
substrate of many processors’ ICs. The temperature
information is provided to the fan-speed regulator and
is read over the SMBus interface. The temperature
data, through the SMBus, can be read as a 10-bit +
sign two’s complement word with a 0.125°C resolution
(LSB) and is updated every 0.25s.
The MAX6660 incorporates a closed-loop fan controller
that regulates fan speed with tachometer feedback. The
temperature information is compared to a threshold and
range setting, which enables the MAX6660 to automati-
cally set fan speed proportional to temperature. Full con-
trol of these modes is available, including being able to
open either the thermal control loop or the fan control
loop. Figure 1 shows a simplified block diagram.
rent is steered through the remote diode, where the for-
ward voltage is measured, and the temperature is com-
puted. The DXN pin is the cathode of the remote diode
and is biased at 0.65V above ground by an internal
diode to set up the ADC inputs for a differential mea-
surement. The worst-case DXP-DXN differential input
voltage range is 0.25V to 0.95V. Excess resistance in
series with the remote diode causes about +1/2°C error
per ohm. Likewise, 200mV of offset voltage forced on
DXP-DXN causes approximately 1°C error.
A/D Conversion Sequence
A conversion sequence is initiated every 250ms in the
free-running autoconvert mode (bit 6 = 0 in the
Configuration register) or immediately by writing a One-
Shot command. The result of the new measurement is
available after the end of conversion. The results of the
previous conversion sequence are still available when
the ADC is converting.
Remote-Diode Selection
Temperature accuracy depends on having a good-
quality, diode-connected small-signal transistor.
Accuracy has been experimentally verified for all
devices listed in Table 1. The MAX6660 can also direct-
ADC
The ADC is an averaging type that integrates over a
60ms period with excellent noise rejection. A bias cur-
_______________________________________________________________________________________
5
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