19-3306; Rev 0; 5/04
2-Channel Temperature Monitor with Dual Automatic
PWM Fan-Speed Controller and Five GPIOs
General Description
The MAX6678 monitors its own temperature and the
temperatures of two external diode-connected transis-
tors, which typically reside on the die of a CPU or other
integrated circuit. The device reports temperature values
in digital form using a 2-wire serial interface. The
MAX6678 provides a programmable alarm output to gen-
erate interrupts, throttle signals, or overtemperature shut-
down signals.
The 2-wire serial interface accepts standard System
Management Bus (SMBus)
™
write byte, read byte, send
byte, and receive byte commands to read the tempera-
ture data and program the alarm thresholds. The tem-
perature data controls a PWM output signal to adjust
the speed of a cooling fan, thereby minimizing noise
when the system is running cool, but providing maxi-
mum cooling when power dissipation increases.
Five GPIO pins provide additional flexibility. The GPIO
power-up states are set by connecting the GPIO preset
inputs to ground or V
CC
.
The MAX6678 is available in a 20-pin QSOP package
and a 5mm x 5mm thin QFN package. It operates from
3.0V to 5.5V and consumes just 500µA of supply current.
♦
Two Thermal-Diode Inputs
♦
Local Temperature Sensor
♦
Five GPIO Input/Outputs
♦
Two PWM Outputs for Fan Drive (Open Drain; May
Be Pulled Up to +5V)
♦
Programmable Fan-Control Characteristics
♦
Automatic Fan Spin-Up Ensures Fan Start
♦
Controlled Rate of Change Ensures Unobtrusive
Fan-Speed Adjustments
♦
1°C Remote Temperature Accuracy (+60°C to
+145°C)
♦
Temperature Monitoring Begins at POR for Fail-
Safe System Protection
♦
OT
Output for Throttling or Shutdown
♦
Four Versions Available, Each with a Different
Address
♦
5mm x 5mm TQFN Package
Features
MAX6678
Applications
Desktop Computers
Notebook Computers
Workstations
Servers
Networking Equipment
SMBus is a trademark of Intel Corp.
PART
MAX6678AEP90
MAX6678AEP92
MAX6678AEP94
MAX6678AEP96
MAX6678ATP90
PWMOUT2
PWMOUT1
PRESET3
GPIO0
Ordering Information
TEMP RANGE
PIN-
PACKAGE
SMBus
ADDRESS
1001000
1001001
1001010
1001011
1001000
1001001
1001010
1001011
-40°C to +125°C 20 QSOP
-40°C to +125°C 20 QSOP
-40°C to +125°C 20 QSOP
-40°C to +125°C 20 QSOP
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
20 Thin
QFN-EP*
20 Thin
QFN-EP*
20 Thin
QFN-EP*
20 Thin
QFN-EP*
Pin Configurations
V
CC
TOP VIEW
MAX6678ATP92
MAX6678ATP94
MAX6678ATP96
20
SMBDATA
19
18
17
16
15
14
OT
GPIO1
GPIO2
GPIO3
PRESET0
1
2
3
4
5
*CONNECT EXPOSED
PADDLE TO GND
SMBCLK
GPIO4
PRESET4
DXP1
MAX6678
13
12
11
10
PRESET1
*EP
= Exposed paddle.
6
DXN
7
DXP2
8
GND
9
PRESET2
5mm x 5mm THIN QFN
Pin Configurations continued at end of data sheet.
Typical Operating Circuit appears at end of data sheet.
________________________________________________________________
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.
2-Channel Temperature Monitor with Dual Automatic
PWM Fan-Speed Controller and Five GPIOs
MAX6678
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ..............................................................-0.3V to +6V
OT,
SMBDATA, SMBCLK, PWMOUT_,
GPIO_ to GND ......................................................-0.3V to +6V
DXP_ to GND ..........................................-0.3V to + (V
CC
+ 0.3V)
DXN to GND ..........................................................-0.3V to +0.8V
PRESET_ to GND ....................................-0.3V to + (V
CC
+ 0.3V)
SMBDATA,
OT,
PWMOUT_ Current....................-1mA to +50mA
DXN Current .......................................................................±1mA
ESD Protection (all pins, Human Body Model) ..................2000V
Continuous Power Dissipation (T
A
= +70°C)
20-Pin QSOP (derate 9.1mW/°C above +70°C).......... 727mW
20-Pin TQFN (derate 34.5mW/°C above +70°C) .......2759mW
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
= +3.0V to +5.5V, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
CC
= +3.3V, T
A
= +25°C.)
PARAMETER
Operating Supply Voltage Range
Operating Current
SYMBOL
V
CC
I
S
Interface inactive, ADC active
+25°C
≤
T
R
≤
+125°C,
T
A
= 60°C
External Temperature Error,
V
CC
= 3.3V
V
CC
= 3.3V
0°C
≤
T
R
≤
+145°C,
+25°C
≤
T
A
≤
+100°C
0°C
≤
T
R
≤
+145°C,
0°C
≤
T
A
≤
+125°C
Internal Temperature Error
Temperature Resolution
Conversion Time
PWM Frequency Tolerance
Remote-Diode Sourcing Current
DXN Source Voltage
DIGITAL INPUTS AND OUTPUTS
Output Low Voltage (Sink Current)
(OT, GPIO_, SMBDATA, PWMOUT_)
Output High Leakage Current
(OT, GPIO_, SMBDATA, PWMOUT_)
Logic-Low Input Voltage (SMBDATA,
SMBCLK, PRESET_, GPIO_)
Logic-High Input Voltage (SMBDATA,
SMBCLK, PRESET_, GPIO_)
Input Leakage Current
Input Capacitance
SMBus TIMING
Serial Clock Frequency
f
SCLK
100
kHz
C
IN
5
V
OL
I
OH
V
IL
V
IH
V
CC
= 3V to 3.6V
V
CC
= 3.6V to 5.5V
V
CC
= 3V to 3.6V
V
CC
= 3.6V to 5.5V
2.1
2.1
1
I
OUT
= 6mA
0.4
1
0.8
0.8
V
µA
V
V
µA
pF
(Note 1)
High level
Low level
V
CC
= +3.3V
+25°C
≤
T
R
≤
+100°C
0°C
≤
T
A
≤
+125°C
1
8
200
-20
80
8
100
10
0.7
250
300
+20
120
12
CONDITIONS
MIN
+3.0
0.5
TYP
MAX
+5.5
1
±1
±3
±4
±2.5
±4
°C
°C
Bits
ms
%
µA
V
°C
UNITS
V
mA
2
_______________________________________________________________________________________
2-Channel Temperature Monitor with Dual Automatic
PWM Fan-Speed Controller and Five GPIOs
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.0V to +5.5V, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
CC
= +3.3V, T
A
= +25°C.)
PARAMETER
Clock Low Period
Clock High Period
Bus Free Time Between Stop and
Start Conditions
SMBus Start Condition Setup Time
Start Condition Hold Time
Stop Condition Setup Time
Data Setup Time
Data Hold Time
SMBus Fall Time
SMBus Rise Time
SMBus Timeout
Startup Time After POR
SYMBOL
t
LOW
t
HIGH
t
BUF
t
SU:STA
t
HD:STO
t
SU:STO
t
SU:DAT
t
HD:DAT
t
F
t
R
t
TIMEOUT
t
POR
29
37
90% of SMBCLK to 90% of SMBDATA
10% of SMBDATA to 10% of SMBCLK
90% of SMBCLK to 10% of SMBDATA
10% of SMBDATA to 10% of SMBCLK
10% of SMBCLK to 10% of SMBDATA
10% to 10%
90% to 90%
CONDITIONS
MIN
4
4.7
4.7
4.7
4
4
250
300
300
1000
55
500
TYP
MAX
UNITS
µs
µs
µs
µs
µs
µs
ns
ns
ns
ns
ms
ms
MAX6678
Note 1:
Deviation from programmed value in Table 6.
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
OPERATING SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6678 toc02
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
FAIRCHILD 2N3906
MAX6678 toc03
600
2
1
TEMPERATURE ERROR (
°
C)
0
-1
-2
-3
-4
560
SUPPLY CURRENT (µA)
520
480
440
400
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
0
25
50
75
100
125
150
TEMPERATURE (
°
C)
_______________________________________________________________________________________
3
2-Channel Temperature Monitor with Dual Automatic
PWM Fan-Speed Controller and Five GPIOs
MAX6678
Typical Operating Characteristics (continued)
(T
A
= +25°C, unless otherwise noted.)
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX6678 toc04
REMOTE TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6678 toc05
LOCAL TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
V
IN
= 250mV
P-P
SQUARE WAVE APPLIED
TO
V
CC
WITH NO BYPASS CAPACITOR
MAX6678 toc06
3
2
TEMPERATURE ERROR (
°
C)
1
0
-1
-2
-3
0
25
50
75
100
2.0
1.5
TEMPERATURE ERROR (
°
C)
1.0
0.5
0
-0.5
-1.0
-1.5
V
IN
= 250mV
P-P
SQUARE WAVE APPLIED
TO
V
CC
WITH NO BYPASS CAPACITOR
1.0
0.5
TEMPERATURE ERROR (
°
C)
0
-0.5
-1.0
-1.5
-2.0
-2.5
125
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
TEMPERATURE (
°
C)
FREQUENCY (kHz)
FREQUENCY (kHz)
REMOTE TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
MAX6678 toc07
REMOTE TEMPERATURE ERROR
vs. DIFFERENTIAL NOISE FREQUENCY
0.9
TEMPERATURE ERROR (
°
C)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
V
IN
= AC-COUPLED TO DXP
V
IN
= 100mV
P-P
SQUARE WAVE
MAX6678 toc08
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
1
TEMPERATURE ERROR (
°
C)
0
-1
-2
-3
-4
-5
-6
T
A
= +25°C
MAX6678 toc09
2.0
1.8
TEMPERATURE ERROR (
°
C)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
IN
= AC-COUPLED TO DXP AND DXN
V
IN
= 100mV
P-P
SQUARE WAVE
1.0
2
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
0.1
1
10
100
FREQUENCY (kHz)
FREQUENCY (kHz)
DXP-DXN CAPACITANCE (nF)
PWMOUT FREQUENCY
vs. DIE TEMPERATURE
MAX6678 toc10
PWMOUT FREQUENCY
vs. SUPPLY VOLTAGE
MAX6678 toc11
GPIO OUTPUT VOLTAGE
vs. GPIO SINK CURRENT
MAX6678 toc12
35
35
500
GPIO OUTPUT VOLTAGE (mV)
PWMOUT FREQUENCY (Hz)
PWMOUT FREQUENCY (Hz)
34
34
400
33
33
300
32
32
200
31
31
100
30
-40
-15
10
60
85
°
C)
TEMPERATURE (
35
110
30
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
0
0
5
10
15
20
25
30
35
40
GPIO SINK CURRENT (mA)
4
_______________________________________________________________________________________
2-Channel Temperature Monitor with Dual Automatic
PWM Fan-Speed Controller and Five GPIOs
Pin Description
PIN
THIN QFN
1
2
3, 12, 13,
14, 16
4, 9, 10,
11, 20
QSOP
3
4
5, 14, 15,
16, 18
2, 6, 11,
12, 13
NAME
SMBDATA
SMBCLK
GPIO0–GPIO4
PRESET0–PRESET4
DESCRIPTION
SMBus Serial-Data Input/Output, Open Drain. Can be pulled up to 5.5V,
regardless of V
CC
. Open circuit when V
CC
= 0.
SMBus Serial-Clock Input. Can be pulled up to 5.5V, regardless of V
CC
. Open
circuit when V
CC
= 0.
Active-Low, Open-Drain GPIO Pins. Can be pulled up to 5.5V, regardless of
V
CC
. Open circuit when V
CC
= 0.
GPIO Preset Inputs. Connect to GND or V
CC
to set POR value of GPIO0–GPIO4.
Combined Current Source and A/D Positive Input for Remote Diode. Connect to
anode of remote-diode-connected temperature-sensing transistor. Do not leave
floating; connect to DXN if no remote diode is used. Place a 2200pF capacitor
between DXP_ and DXN for noise filtering.
Combined Remote-Diode Cathode Input. Connect cathode of the remote-diode-
connected transistor to DXN.
Ground. Connect to a clean ground reference.
Active-Low, Open-Drain Over-Temperature Output. Typically used for system
shutdown or clock throttling. Can be pulled up to 5.5V regardless of V
CC
. Open
circuit when V
CC
= 0.
Open-Drain Output to Power Transistor Driving Fan. Connect to the gate of a
MOSFET or base of a transistor. PWMOUT_ requires a pullup resistor. The
pullup resistor can be connected to a supply voltage as high as 5.5V,
regardless of the MAX6678’s supply voltage.
Power-Supply Input. 3.3V nominal. Bypass V
CC
to GND with 0.1µF capacitor.
MAX6678
5, 7
7, 9
DXP1, DXP2
6
8
15
8
10
17
DXN
GND
OT
17, 19
1, 19
PWMOUT1,
PWMOUT2
V
CC
18
20
Block Diagram
V
CC
Detailed Description
The MAX6678 temperature sensor and fan controller
accurately measures the temperature of either two
remote pn junctions or one remote pn junction and its
own die. The device reports temperature values in digi-
tal form using a 2-wire serial interface. The remote pn
junction is typically the emitter-base junction of a com-
mon-collector pnp on a CPU, FPGA, or ASIC. The
MAX6678 operates from supply voltages of 3.0V to
5.5V and consumes 500µA (typ) of supply current. The
temperature data controls a PWM output signal to
adjust the speed of a cooling fan. The device also fea-
tures an overtemperature alarm output to generate
interrupts, throttle signals, or shutdown signals.
Five GPIO input/outputs provide additional flexibility.
The GPIO power-up states are set by connecting the
GPIO preset inputs to ground or V
CC
.
DXP1
DXN
DXP2
TEMPERATURE
PROCESSING
BLOCK
PWM
GENERATOR
BLOCK
PWMOUT1
PWMOUT2
OT
LOGIC
SMBus
INTERFACE
AND
REGISTERS
GPIO0
GPIO4
PRESET0
PRESET4
SMBCLK
SMBDATA
MAX6678
GND
_______________________________________________________________________________________
5
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