Rainbow Electronics MAX6661 User Manual
General Description
The MAX6661 is a remote temperature sensor and fanspeed regulator that provides complete closed-loop fan
control. The remote temperature sensor is typically a
common-collector PNP, such as a substrate PNP of a
microprocessor, or a diode-connected transistor, typically a low-cost, easily mounted 2N3904 NPN type or
2N3906 PNP type.
The device also incorporates a closed-loop fan controller that regulates fan speed with tachometer feedback. The MAX6661 compares temperature data to a
fan threshold temperature and gain setting, both programmed over the SPI™ bus by the user. The result is
automatic fan control that is proportional to the remotejunction 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 maximizing fan reliability. An on-chip power device drives
fans rated up to 250mA.
Temperature data is updated every 500ms and is readable at any time over the SPI interface. The MAX6661 is
accurate to 1°C (max) when the remote junction is
between +60°C to +100°C. Data is formatted as a 10bit + sign word with 0.125°C resolution.
The MAX6661 is specified between -40°C to +125°C
and is available in a 16-pin QSOP package.
Applications
Telecom Systems
Servers
Workstations
Electronic Instruments
Features
♦ Integrated Thermal Measurement and Fan
Regulation
♦ 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
♦ SPI-Compatible Serial Interface
♦ ±1°C (+60°C to +100°C) Thermal-Sensing
Accuracy
MAX6661
Remote Temperature-Controlled Fan-Speed
Regulator with SPI-Compatible Interface
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
1µF
5kΩ
FAN
12V
2200pF
PENTIUM
SDIN
SC
ALERT
OVERT
SPI CLOCK
SPI DATA IN
DOUT
SPI DATA OUT
CS
SPI CHIP SELECT
INTERRUPT
TO µP
TO SYSTEM
SHUTDOWN
V
FAN
PGND
0.1µF
3V TO 5.5V
50Ω
V
CC
TACH IN
FAN
DXP
DXN
AGND
10kΩ
EACH
MAX6661
Typical Operating Circuit
19-2337; Rev 0; 1/02
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.
Pin Configuration appears at end of data sheet.
SPI is a trademark of Motorola, Inc.
PART TEMP RANGE PIN-PACKAGE
MAX6661AEE -40°C to +125°C 16 QSOP
MAX6661
Remote Temperature-Controlled Fan-Speed
Regulator with SPI-Compatible Interface
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC= 3V to 5.5V, V
FAN
= 12V, TA= -40°C to +125°C, unless otherwise specified. Typical values are at VCC= 3.3V and TA=
+25°C.) (Notes 1 and 2)
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.
VCC, ALERT, OVERT ...............................................-0.3V to +6V
V
FAN
, TACH IN, FAN .............................................-0.3V to +16V
DXP, CS, SDOUT, GAIN, SCL, SDIN..........-0.3V to (V
CC
+ 0.3V)
DXN ..........................................................................-0.3V to +1V
SDOUT Current ...................................................-1mA to +50mA
DXN Current ......................................................................±1mA
FAN Out Current ..............................................................500mA
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
ADC AND POWER SUPPLY
Temperature Resolution
(Note 3)
Remote-Junction Temperature
Measurement Error (Note 4)
Fan-Speed Measurement
Accuracy
VCC Supply Voltage Range V
V
FAN
Conversion Time 0.25 s
Conversion Rate Timing Error -25 +25 %
Undervoltage Lockout (UVLO)
Threshold
UVLO Threshold Hysteresis V
POR Threshold (VCC)V
POR Threshold Hysteresis 90 mV
Standby Supply Current I
Operating Supply Current I
DXN Source Voltage V
TACH Input Transition Level V
TACH Input Hysteresis V
TACH Input Resistance 250 kΩ
Fan Output Current I
Fan Output Current Limit I
Fan Output On-Resistance R
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage Range V
TRJ = +60°C to +100°C-1 +1°C
TRJ = +25°C to +125°C-3 +3°C
T
= -40°C to +125°C-5 +5°C
RJ
T
E
CC
FAN
V
UVLOVCC
HYST
SHDN
CC
DXN
F
L
ONF
TA = +85°C,
= 3.3V
V
CC
falling 2.50 2.80 2.95 V
rising 1.4 2.0 2.5 V
CC
Shutdown, configuration bit 6 = 1 3 20 µA
Fan off 450 700 µA
= 12V 10.5 V
FAN
= 12V 190 mV
FAN
(Note 5) 320 410 mA
250mA load 4 Ω
0.125 °C
11 Bits
±25 %
3.0 5.5 V
4.5 13.5 V
90 mV
0.7 V
250 mA
MAX6661
Remote Temperature-Controlled Fan-Speed
Regulator with SPI-Compatible Interface
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC= 3V to 5.5V, V
FAN
= 12V, TA= -40°C to +125°C, unless otherwise specified. Typical values are at VCC= 3.3V and TA=
+25°C.) (Notes 1 and 2)
Note 1: T
A
= TJ. This implies zero dissipation in pass transistor (no load, or fan turned off).
Note 2: All parameters are 100% production tested at a single temperature, unless otherwise indicated. Parameter values through
temperature are guaranteed by design.
Note 3: The fan control section of the MAX6661 and temperature comparisons use only 9 bits of the 11-bit temperature measure-
ment with a 0.5°C LSB.
Note 4: Wide-range accuracy is guaranteed by design, not production tested.
Note 5: Guaranteed by design.
INTERFACE PINS (SDIN, SC, CS, DOUT, ALERT, OVERT)
Serial Bus Maximum Clock
Frequency (Note 5)
Logic Input High Voltage
Logic Input Low Voltage VCC = 3V to 5V 0.8 V
Logic Output High-Voltage
DOUT
Logic Output Low-Voltage DOUT VCC = 3V, I
Logic Output Low-Voltage
ALERT, OVERT
ALERT, OVERT Output
High Leakage Current
Logic Input Current Logic inputs forced to VCC or GND -2 2 µA
SPI AC TIMING (Figure 5)
CS High to DOUT Three-State t
CS to SC Setup Time t
SC Fall to DOUT Valid t
DIN to SC Setup Time t
DIN to SC Hold Time t
SC Period t
SC High Time t
SC Low Time t
CS High Pulse Width t
Output Rise Time t
Output Fall Time t
SC Falling Edge to CS Rising
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SC 2.5 MHz
VCC = 3V 2.2
V
= 5.5V 2.4
CC
V
-
CC
0.4V
200 ns
400 ns
200 ns
200 ns
TR
CSS
DO
DS
DH
CP
CH
CL
CSW
R
F
t
SCS
= 3V, I
V
CC
= 3V, I
V
CC
ALERT, OVERT forced to 5.5V 1 µA
= 100pF, R
C
LOAD
(Note 5) 200 ns
C
= 100pF 200 ns
LOAD
(Note 5) 200 ns
(Note 5) 400 ns
C
= 100pF 10 ns
LOAD
= 100pF 10 ns
C
LOAD
(Note 5) 200 ns
= 6mA (Note 5)
SOURCE
= 6mA (Note 5) 0.4 V
SINK
= 6mA (Note 5) 0.4 V
SINK
= 10kΩ (Note 5) 200 ns
GS
V
V
MAX6661
Remote Temperature-Controlled Fan-Speed
Regulator with SPI-Compatible Interface
4 _______________________________________________________________________________________
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
1 10 100
TEMPERATURE ERROR
vs. PC BOARD RESISTANCE
MAX6661 toc01
LEAKAGE RESISTANCE (MΩ)
TEMPERATURE ERROR (°C)
20
-30
-25
-20
-15
-10
-5
0
15
10
5
PATH = DXP TO GND
PATH = DXP TO VCC (5V)
-5
-2
-3
-4
-1
0
1
2
3
4
5
-50 0 50 100 150
MAX6661 toc02
TEMPERATURE (°C)
TEMPERATURE ERROR (°C)
TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
1 100 10k 1M10 1k 100k 10M 100M
TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6661 toc03
FREQUENCY (Hz)
TEMPERATURE ERROR (°C)
20
-30
-25
-20
-15
-10
-5
0
15
10
5
VIN = 100mV
P-P
VIN = SQUARE WAVE APPLIED TO V
CC
WITH NO 0.1µF VCC CAPACITOR
VIN = 250mV
P-P
4.0
-1.5
-1.0
MAX6661 toc04
FREQUENCY (Hz)
TEMPERATURE ERROR (°C)
-0.5
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
1 10 100M1M 10M100 1k 10k 100k
TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
VIN = 50mV
P-P
VIN = SQUARE WAVE
AC-COUPLED TO DXN
VIN = 100mV
P-P
VIN = 25mV
P-P
-8
-6
-7
-4
-5
-3
-2
0
-1
1
0102030405060708090100
MAX6661 toc05
DXP-DXN CAPACITANCE (nF)
TEMPERATURE ERROR (°C)
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
0
1
3
2
4
5
MAX6661 toc06
SUPPLY VOLTAGE (V)
STANDBY SUPPLY CURRENT (µA)
3.0 4.0 4.53.5 5.0 5.5
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
CONFIG BIT 6 = 1
3.0 3.9 4.23.3 3.6 4.5 4.8 5.1 5.4
MAX6661 toc07
SUPPLY VOLTAGE (V)
AVERAGE SUPPLY CURRENT (µA)
450
AVERAGE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
Detailed Description
The MAX6661 is a remote temperature sensor and fan
controller with an SPI interface. The MAX6661 converts
the temperature of a remote PN junction to a 10-bit +
sign digital word. The remote PN junction 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 SPI interface.
The temperature data, through the SPI interface, can be
read as a 10-bit + sign two’s complement word with a
0.125°C resolution (LSB) and is updated every 0.5s.
The MAX6661 incorporates a closed-loop fan controller
that regulates the fan speed with tachometer feedback.
The temperature information is compared to a threshold
and range setting, which enables the MAX6661 to automatically set fan speed proportional to temperature.
Full control of the fan is available by being able to open
either the thermal control loop or the fan control loop.
Figure 1 shows a simplified block diagram.
ADC
The ADC is an averaging type that integrates the signal
input over a 125ms period with excellent noise rejection. A bias current is steered through the remote
diode, where the forward voltage is measured, and the
temperature is computed. The DXN pin is the cathode
of the remote diode and is biased at 0.7V above
ground by an internal diode to set up the ADC inputs
for a differential measurement. The worst-case DXPDXN 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 temperature-conversion sequence is initiated every
500ms 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 goodquality, diode-connected, small-signal transistor.
Accuracy has been experimentally verified for all
devices listed in Table 1. The MAX6661 can also directly measure the die temperature of CPUs and other ICs
that have on-board temperature-sensing diodes.
MAX6661
Remote Temperature-Controlled Fan-Speed
Regulator with SPI-Compatible Interface
_______________________________________________________________________________________ 5
Pin Description
PIN NAME FUNCTION
1V
2VCCPower Supply: 3V to 5.5V. Bypass with a 0.1µF capacitor to GND.
3 DXP Input: Remote-Junction Anode. Place a 2200pF capacitor between DXP and DXN for noise filtering.
4 DXN Input: Remote-Junction Cathode. DXN is internally biased to a diode voltage above ground.
5 FAN Output to Fan Low Side
6 N.C. No External Connection. Must be left floating.
7 PGND Power Ground
8 AGND Analog Ground
9 OVERT Output to System Shutdown. Active-low output, programmable for active high, if desired. Open drain.
10 CS SPI Chip Select. Active low.
11 ALERT Open-Drain Active-Low Output
12 DOUT SPI Data Output. High-Z when not being read.
13 GAIN
14 SCL SPI Clock
15 SDIN SPI Data In
16 TACH IN Fan Tachometer Input. 13.5V tolerant, pullup from V
FAN
Power Supply for Fan Drive: 4.5V to 13.5V
Leave open if tachometer feedback is being used. Connect an external resistor to V
gain of the current sense.
to 13.5V is allowed on this line.
CC
to reduce the
CC
MAX6661
Remote Temperature-Controlled Fan-Speed
Regulator with SPI-Compatible Interface
6 _______________________________________________________________________________________
Figure 1. MAX6661 Block Diagram
VFAN
DXN
SC
SDIN
DOUT
CS
FAN-SPEED
REGULATOR
REGISTERS
T
MAX
MUXDXP
ADC
CONTROL
LOGIC
SPI
INTERFACE
T
HYST
REMOTE
TEMPERATURE
DATA
T
HIGH
T
LOW
CONFIGURATION
FAN TACHOMETER
DIVISOR (FTD)
T
(FT)
FAN
FAN GAIN (FG)
COMPARAT0R
THERMAL OPEN/
CLOSE LOOP
FAN OPEN/
CLOSE LOOP
FAN
CONTROL
CIRCUIT
TACH IN
FAN
N
FAN
OVERT
ALERT
FULL SCALE
(FS)
FAN TACHOMETER
PERIOD LIMIT (FTPL)
MODE (M)
FAN-CONVERSION
RATE (FCR)
FAN-SPEED CONTROL
(FSC)
STATUS
FAN TACHOMETER
PERIOD (FTP)
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