MAXIM MAX1669

19-1574; Rev 0; 1/00
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
Features
The MAX1669 fan controller includes a precise digital
thermometer that reports the temperature of a remote
sensor. The remote sensor is a diode-connected transistor—typically a low-cost, easily mounted 2N3906 PNP
type—replacing conventional thermistors or thermocouples. Remote accuracy is ±3°C for transistors from multiple manufacturers, with no calibration needed. The
MAX1669 has an independent fan controller with a lowcurrent logic output requiring external power components to interface to a DC brushless fan. The fan
controller has two modes of operation: a low-frequency
(20Hz to 160Hz) PWM mode intended for driving the fan
motor, or a high-impedance DAC output that generates
a variable DC control voltage. In PWM mode, the FAN
frequency can be synchronized to an external clock.
♦ Measures Remote CPU Temperature
Other key features include general-purpose inputs/outputs (GPIOs) for fan presence detection and a thermostat output intended as a fan override signal in case the
host system loses the ability to communicate. The internal ADC has a wide input voltage range and gives
overrange readings when too large an input voltage is
applied. Other error-checking includes temperature
out-of-range indication and diode open/short faults.
♦ Supports SMBus Alert Response
♦ No Calibration Required
♦ 20Hz to 160Hz PWM Output for Fan
♦ PWM Frequency Sync Input (260kHz)
♦ Flexible Fan Interface: Linear or PWM
♦ SMBus 2-Wire Serial Interface
♦ Programmable Under/Overtemperature Alarms
♦ ALERT Latched Interrupt Output
♦ OVERT Thermostat Output
♦ Two GPIO Pins
♦ Write-Once Configuration Protection
♦ ±3°C Temperature Accuracy (-40°C to +125°C,
remote)
♦ 3µA Standby Supply Current
♦ +3V to +5.5V Supply Range
♦ Small 16-Pin QSOP Package
The MAX1669 is available in a space-saving 16-pin
QSOP package that allows it to fit adjacent to the
SLOT1 connector.
Applications
Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX1669EEE
-40°C to +85°C
16 QSOP
Pentium® CPU Cooling
Desktop Computers
Pin Configuration
Notebook Computers
Servers
Workstations
TOP VIEW
Typical Operating Circuit appears at end of data sheet.
I/O1 1
16 OVERT
I/O2 2
15 ALERT
ADD0 3
ADD1 4
14 SMBDATA
MAX1669
13 SMBCLK
ADD2 5
12 PGND
AGND 6
11 FAN
DXN 7
10 SYNC
DXP 8
9
VCC
QSOP
Pentium is a registered trademark of Intel Corp.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX1669
General Description
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
ABSOLUTE MAXIMUM RATINGS
VCC to AGND...........................................................-0.3V to +6V
DXP, ADD_ to AGND.................................-0.3V to (VCC + 0.3V)
DXN to AGND.......................................................-0.3V to +0.8V
SMBCLK, SMBDATA, ALERT, SYNC,
I/O1, I/O2, OVERT, FAN to AGND ......................-0.3V to +6V
FAN to PGND ............................................-0.3V to (VCC + 0.3V)
PGND to AGND ....................................................-0.3V to +0.3V
PWM Current....................................................-50mA to +50mA
SMBDATA Current .............................................-1mA to +50mA
I/O1, I/O2 Current...............................................-1mA to +25mA
DXN Current ......................................................................±1mA
ESD Protection (all pins, Human Body Model) .................2000V
Continuous Power Dissipation (TA = +70°C)
16-Pin QSOP (derate 8.30mW/°C above +70°C).......667mW
Operating Temperature Range (extended) ......-55°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
(VCC = +3.3V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ADC AND POWER SUPPLY
Resolution (Note 1)
Monotonicity guaranteed
8
Temperature Error, Remote Diode (Note 2)
TR = 0°C to +100°C, diode ideality factor = 1.013
-3
3
°C
3
5.5
V
2.95
V
Supply Voltage Range
Undervoltage Lockout Threshold
VCC input, disables A/D conversion,
rising edge
2.6
2.8
VCC, falling edge
1
1.9
50
Undervoltage Lockout Hysteresis
Power-On Reset Threshold
Average Operating Supply Current
mV
2.5
50
POR Threshold Hysteresis
Standby Supply Current
Bits
SMBus static
3
SMBCLK at 10kHz
3
FAN output set to
150Hz mode
Autoconvert mode,
average measured over 1s FAN output set to
DAC mode
75
V
mV
10
150
360
µA
µA
µA
Conversion Time
From stop bit to conversion complete
47
62
78
ms
Conversion Rate
Autoconvert mode
1.6
2
2.4
Hz
Remote-Diode Source Current
VDXP forced to VDXN
+ 0.65V
High level
80
100
120
Low level
8
10
12
0.7
DXN Source Voltage
µA
V
FAN OUTPUT
FAN Output Source Current
PWM mode, VFAN forced to 2.9V
FAN Output Sink Current
PWM mode, VFAN forced to 0.4V
2
10
_______________________________________________________________________________________
mA
-10
mA
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
(VCC = +3.3V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
FAN PWM Frequency Error
PWM mode, any setting
-20
+20
%
FAN Total Unadjusted Error
DAC mode, any setting, RL = 10kΩ to GND
-4
4
%FS
FAN Output Voltage High
DAC mode, FAN duty factor = 1111b,
IOUT = 5mA
FAN Output Voltage Low
DAC mode, FAN duty factor = 0000b,
IOUT = -5mA
2.96
3.06
V
0.05
0.2
V
260
400
kHz
SYNC Capture Range
140
SYNC Input High Period
500
ns
SYNC Input Low Period
500
ns
2.1
V
SMBus INTERFACE (Figures 7, 8)
Logic Input High Voltage
ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA;
VCC = 3V to 5.5V
Logic Input Low Voltage
ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA;
VCC = 3V to 5.5V
SMBDATA, ALERT, OVERT, I/O1, I/O2
Output Low Sink Current
Pin forced to 0.4V
ALERT, OVERT, I/O1, I/O2 Output
High Leakage Current
Pin forced to 5.5V
Logic Input Current
Logic inputs forced to VCC or GND
SMBus Input Capacitance
SMBCLK, SMBDATA
SMBus Clock Frequency
(Note 3)
DC
SMBCLK Clock Low Time (tLOW)
10% to 10% points
4.7
µs
SMBCLK Clock High Time (tHIGH)
90% to 90% points
4
µs
SMBus Rise Time
SMBCLK, SMBDATA, 10% to 90% points
1
µs
SMBus Fall Time
SMBCLK, SMBDATA, 90% to 10% points
300
ns
SMBus Start Condition Setup Time
0.8
6
V
mA
-1
1
µA
1
µA
5
pF
100
kHz
4.7
µs
500
ns
SMBus Repeated Start Condition Setup
Time (tSU:STA)
90% to 90% points
SMBus Start Condition Hold Time (tHD:STA)
10% of SMBDATA to 90% of SMBCLK
4
µs
SMBus Stop Condition Setup Time (tSU:STO) 90% of SMBCLK to 10% of SMBDATA
4
µs
250
ns
0
µs
4.7
µs
SMBus Data Valid to SMBCLK
Rising-Edge Time (tSU:DAT)
10% or 90% of SMBDATA to 10% of SMBCLK
SMBus Data-Hold Time (tHD:DAT)
(Note 4)
SMBus Bus-Free Time (tBUF)
Between start/stop conditions
SMBCLK Falling Edge to SMBus
Data-Valid Time
Master clocking-in data
1
µs
_______________________________________________________________________________________
3
MAX1669
ELECTRICAL CHARACTERISTICS (continued)
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
ELECTRICAL CHARACTERISTICS
(VCC = +3.3V, TA = -40°C to +85°C, unless otherwise noted.) (Note 5)
PARAMETER
CONDITIONS
MIN
MAX
UNITS
ADC AND POWER SUPPLY
Temperature Resolution (Note 1)
Monotonicity guaranteed
8
Temperature Error, Remote Diode (Note 2)
TR = -55°C to +125°C, diode ideality factor = 1.013
-5
5
°C
3
5.5
V
100
µA
Supply Voltage Range
Average Operating Supply Current
Autoconvert mode, average measured over
1sec, FAN output set to 150Hz mode
Conversion Time
From stop bit to conversion complete
47
Conversion Rate
Autoconvert mode
1.6
FAN Output Source Current
PWM mode, VFAN forced to 2.9V
10
FAN Output Sink Current
PWM mode, VFAN forced to 0.4V
FAN PWM Frequency Error
PWM mode, any setting
FAN Total Unadjusted Error
DAC mode, any setting, RL = 10kΩ to GND
FAN Output Voltage High
DAC mode, FAN duty factor = 1111b,
IOUT = 5mA
FAN Output Voltage Low
DAC mode, FAN duty factor = 0000b,
IOUT = -5mA
Bits
ms
2.4
Hz
FAN OUTPUT
mA
-10
mA
-25
+25
%
-5
5
%FS
2.94
V
0.2
V
SMBus INTERFACE
Logic Input High Voltage
ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA;
VCC = 3V to 5.5V
Logic Input Low Voltage
ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA;
VCC = 3V to 5.5V
SMBDATA, ALERT, OVERT, I/O1, I/O2
Output Low Sink Current
Pin forced to 0.4V
ALERT, OVERT, I/O1, I/O2 Output
High Leakage Current
Pin forced to 5.5V
Logic Input Current
Logic inputs forced to VCC or GND
2.1
V
0.8
6
-1
V
mA
1
µA
1
µA
Note 1: Guaranteed but not 100% tested.
Note 2: TR is the junction temperature of the remote diode. The temperature error specification is optimized to and guaranteed for a
diode-connected 2N3906 transistor with ideality factor = 1.013. Variations in the ideality factor “m” of the actual transistor
used will increase the temperature error by *. See the Temperature Error vs. Remote Diode Temperature graph in the
Typical Operating Characteristics for typical temperature errors using several random 2N3906s. See Remote Diode
Selection for remote diode forward-voltage requirements.
Note 3: The SMBus logic block is a static design that works with clock frequencies down to DC. While slow operation is possible, it
violates the 10kHz minimum clock frequency and SMBus specifications, and may monopolize the bus.
Note 4: 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 5: Specifications to -40°C are guaranteed by design and not production tested.
 1.013

* ∆T = 
− 1 273.15k + TR
 m

(
4
) (°C)
_______________________________________________________________________________________
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
TEMPERATURE ERROR
vs. REMOTE DIODE TEMPERATURE
0
-10
-20
PATH = DXP TO VCC (5V); CONFIG = 02h
MAX1669-02
1.0
0.5
0
-0.5
-1.0
14
12
10
6
2
0
-40
-2.0
-2
TEMPERATURE ERROR
vs. DXP - DXN CAPACITANCE
C = 2200pF
4
3
C = 27nF
2
1
MAX1669-05
-4
-6
-8
-10
-12
-1
-14
100M
1G
100M
7
6
5
4
3
2
0
0
10
FREQUENCY (Hz)
20
30
40
50
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
DXP-DXN CAPACITANCE (nF)
PWM FREQUENCY vs. CODE (F3F2F1F0)
RESPONSE TO THERMAL SHOCK
180
MAX1669-07
120
100
160
140
PWM FREQUENCY (Hz)
TEMPERATURE (°C)
10M
80
60
40
MAX1669-08
10M
1M
1
-16
1M
100K
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
-2
0
-2
VCC = 5V
0
TEMPERATURE ERROR (°C)
5
2
MAX1669-04
6
10K
PSNF (Hz)
TEMPERATURE ERROR vs.
COMMON-MODE NOISE FREQUENCY
VIN = 50mVp-p AC-COUPLED TO DXN
C = DXN - DXP CAPACITANCE
1K
20 40 60 80 100 120 140
TEMPERATURE (°C)
8
7
-60 -40 -20 0
LEAKAGE RESISTANCE (MΩ)
STANDBY SUPPLY CURRENT (µA)
100
VIN = 100mVp-p
4
-1.5
10
VIN = 250mVp-p
8
-30
1
VIN = SQUARE WAVE APPLIED TO
VCC WITH NO 0.1µF VCC CAPACITOR
MAX1669-06
PATH = DXP TO GND; CONFIG = 02h
10
18
16
TEMPERATURE ERROR (°C)
20
RANDOM 2N3906s FROM
DIFFERENT MANUFACTURERS
1.5
TEMPERATURE ERROR (°C)
TEMPERATURE ERROR (°C)
30
TEMPERATURE ERROR (°C)
2.0
MAX1669-01
40
TEMPERATURE ERROR vs.
POWER-SUPPLY NOISE FREQUENCY
MAX1669-03
TEMPERATURE ERROR
vs. LEAKAGE RESISTANCE
VCC = +5V
120
VCC = +3.3V
100
80
60
40
20
CMPT3906 IMMERSED IN
+115°C FLUORINERT BATH
0
-2
0
2
4
TIME (sec)
6
8
10
20
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
CODE (F3F2F1F0)
_______________________________________________________________________________________
5
MAX1669
Typical Operating Characteristics
(Temperature error = measured - actual, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(Temperature error = measured - actual, TA = +25°C, unless otherwise noted.)
PWM DUTY FACTOR vs. CODE (D3D2D1D0)
4.5
80
MAX1669-10
VCC = +3.3V OR +5V
DAC OUTPUT vs. CODE (D3D2D1D0)
5.0
MAX1669-09
100
ILOAD = +10mA TO -10mA
VCC = +5V
4.0
DAC OUTPUT (V)
DUTY FACTOR (%)
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
60
40
3.5
3.0
2.5
2.0
1.5
20
1.0
0.5
0
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
CODE (D3D2D1D0)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
CODE (D3D2D1D0)
Pin Description
6
PIN
NAME
FUNCTION
1
I/O1
General-Purpose Open-Drain Logic Input/Output 1. I/O1 is intended for driving LEDs, driving power-plane
switching MOSFETs, or detecting fan presence or chassis intrusion.
2
I/O2
General-Purpose Open-Drain Logic Input/Output 2. I/O2 is intended for driving LEDs, driving power-plane
switching MOSFETs, or detecting fan presence or chassis intrusion.
3
ADD0
SMBus Address Select Pin 0. See Table 11.
4
ADD1
SMBus Address Select Pin 1. See Table 11.
5
ADD2
SMBus Address Select Pin 2. See Table 11.
6
AGND
Analog Ground
7
DXN
Combined Current Sink and ADC Negative Input from Remote Diode. DXN is normally biased to a diode
voltage above ground.
8
DXP
Combined Current Source and ADC Positive Input from Remote Diode. Place a 2200pF capacitor
between DXP and DXN for noise filtering.
9
VCC
Supply Voltage Input, +3V to +5.5V. Bypass to AGND with a 0.1µF capacitor.
10
SYNC
Oscillator Synchronization Input. Connect to AGND to use internal clock. Capture range is 140kHz to
400kHz. The synchronization signal is internally applied to the FAN PWM clock. See Table 5 for synchronized frequencies.
11
FAN
Fan-Control Logic Output. Swings from PGND to VCC in PWM mode, or PGND to 0.94 · VCC in DAC mode.
12
PGND
13
SMBCLK
14
SMBDATA
15
ALERT
Active-Low, Open-Drain SMBus Alert (interrupt) Output
16
OVERT
Active-Low, Open-Drain Thermostat Output. Activated by TCRIT threshold
Power Ground
SMBus Serial-Clock Input
Open-Drain SMBus Serial-Data Input/Output
_______________________________________________________________________________________
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
MAX1669
VCC
ADDRESS
DECODER
ADD0
ADD1
ADD2
DXP
DXN
MUX
SMBDATA
ADC
SMB
CONTROL
LOGIC
SMBCLK
GND
READ
WRITE
8
8
COMMAND-BYTE
(INDEX) REGISTER
8
REMOTE-TEMPERATURE
DATA REGISTER
CONFIGURATION
BYTE REGISTER
HIGH-TEMPERATURE
THRESHOLD
STATUS BYTE REGISTER
LOW-TEMPERATURE
THRESHOLD
ALERT RESPONSE
ADDRESS REGISTER
8
MAX1669
8
ALERT
R
DIGITAL COMPARATOR
S
CONTROL
LOGIC
Q
TEMPERATURE SENSOR
I/O1
GENERAL-PURPOSE
I/O CONTROLLER
OVERT
I/O2
-5°C
R
Q
TEMPERATURE
S
CONTROL
LOGIC
TCRIT
Figure 1. MAX1669 Temperature Sensor Functional Diagram
_______________Detailed Description
The MAX1669 temperature sensor is designed to work
with an external microcontroller (µC) or other intelligent
devices in computer fan-control applications. The µC is
typically a power-management or keyboard controller,
generating SMBus serial commands by “bit-banging’’
general-purpose input/output (GPIO) pins or through a
dedicated SMBus interface block.
Essentially an 8-bit serial analog-to-digital converter
(ADC) with a sophisticated front end, the temperature
measurement channel contains a switched-current
source, a multiplexer, and an integrating ADC.
Temperature data from the ADC is loaded into a data
register, where it is automatically compared with data
previously stored in over/undertemperature alarm registers and the critical register (Figure 1).
_______________________________________________________________________________________
7
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
The PWM or DAC fan control circuitry is completely
independent from the temperature measurement, and
software closes the temperature-control feedback loop
(Figure 2).
ADC and Multiplexer
The ADC is an averaging type that integrates over a
62ms period (typ), with excellent noise rejection. The
multiplexer automatically steers bias currents through
the remote diode, measures the forward voltage, and
calculates the temperature.
FREQ
REGISTER
MAX1669
PWM
CONTROLLER
MUX
DUTY
REGISTER
DRIVER
FAN
DAC
(0XF0)
UPPER NIBBLE
4
AND
FANON
OVERT
CONTROL
LOGIC
Figure 2. MAX1669 Fan-Control Functional Diagram
The DXN input is biased at 0.7V above ground by an
internal diode to set up the analog-to-digital (A/D)
inputs for a differential measurement. The worst-case
DXP-DXN differential input voltage range is 0.21V to
0.95V. Diode voltages that are outside the ADC input
range cause overrange indications rather than nonmonotonic readings. Overrange readings will return
+127°C. Excess resistance in series with the remote
diode causes approximately +1/2°C error/Ω. Likewise,
200µV of offset voltage forced on DXP-DXN causes
approximately +1°C error.
A/D Conversion Sequence
When the device is taken out of standby mode, the
result of the measurement is available one conversion
time later (78ms max). If the ADC is busy, the results of
the previous conversion are always available. Toggling
the standby mode on and off is a good way to initiate a
new conversion since this action resets the rate timer.
Low-Power Standby Mode
Supply-current drain during the 62ms conversion period is 500µA. Between conversions, the instantaneous
8
supply current is 18µA. In standby mode, supply current drops to 3µA and the fan output is disabled.
SMBus Digital Interface
From a software perspective, the MAX1669 appears as
a set of byte-wide registers that contain temperature
data, alarm threshold values, or control bits. A standard
SMBus 2-wire serial interface is used to read temperature data and write control bits and alarm threshold
data.
The MAX1669 employs four standard SMBus protocols:
write byte, read byte, send byte, and receive byte
(Figure 3). The two shorter protocols (receive and
send) allow quicker transfers, provided that the correct
data register was previously selected by a write or read
byte instruction. Use caution with the shorter protocols
in multimaster systems since a second master could
overwrite the command byte without informing the first
master.
The temperature data format is 7 bits plus sign in two’s
complement form for each channel, with the LSB representing +1°C (Table 1), MSB transmitted first.
Measurements are offset by +1/2°C to minimize internal
rounding errors; for example, +99.5°C to +100.4°C is
reported as +100°C.
Alarm Threshold Registers
Three registers store alarm threshold data, with hightemperature (THIGH) and low-temperature (TLOW) registers that activate the ALERT output, and a critical
overtemperature register (T CRIT ) that activates the
OVERT output. If a measured temperature equals or
exceeds the THIGH or TLOW threshold value, an ALERT
interrupt is asserted. Do not set the TCRIT register to
values outside of the temperatures in Table 1.
The power-on-reset (POR) state of the THIGH register is
full scale (0111 1111b or +127°C). The POR state of the
TLOW register is 1100 1001b or -55°C. The POR state of
the TCRIT register is 0110 0100b or +100°C.
OVERT Thermostat Output
The OVERT output is a self-clearing interrupt output
that is activated when the temperature equals or
exceeds TCRIT. OVERT normally goes low when active,
but this polarity can be changed through the configuration register. The latch is cleared when the temperature
reading is equal to or less than TCRIT minus 5°C, which
provides for 5°C of hysteresis.
The ALERT and OVERT comparisons are made after
each conversion, and at the end of a write command to
their respective temperature limit registers. For example, if the limit is changed while the device is in standby
_______________________________________________________________________________________
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
MAX1669
Write Byte Format
S
ADDRESS
WR
ACK
COMMAND
ACK
DATA
ACK
P
1
7 bits
1
1
8 bits
1
8 bits
1
1
7-bit slave address:
equivalent to chip-select line
Command byte: selects which
register you are writing to
Data byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
Read Byte Format
S
ADDRESS
WR
ACK
COMMAND
ACK
S
ADDRESS
RD
ACK
DATA
A
P
1
7 bits
1
1
8 bits
1
1
7 bits
1
1
8 bits
1
1
Slave address:
equivalent to chip-select
line
S = Start condition
P = Stop condition
Command byte: selects
which register you are
reading from
Slave address: repeated
due to change in dataflow direction
Data byte: reads from
the register set by the
command byte
Shaded = Slave transmission
A = Not acknowledged
Figure 3. SMBus Protocols
Table 1. Data Format (Two’s Complement)
DIGITAL OUTPUT
DATA BITS
SIGN
MSBs
LSBs
mode, the ALERT and OVERT outputs respond correctly according to the last valid A/D result.
Note that the ALERT output does not respond to TCRIT
(OVERT) comparisons.
The OVERT latch can implement an override control to
the FAN output, which forces the fan to VCC whenever
the TCRIT threshold is crossed. This override switch is
the backup fan control loop, and is enabled through the
FAN ON bit in the configuration register (bit 2). Note
that changing the duty to 100% in this way doesn’t
affect the contents of the DUTY register, and the FAN
output reverts to the preprogrammed duty factor (or
DAC voltage) when the OVERT latch is reset.
TEMP (°C)
ROUNDED
TEMP (°C)
+130.00
+127
0
111
1111
+127.00
+127
0
111
1111
+126.50
+127
0
111
1111
+126.00
+126
0
111
1110
+25.25
+25
0
001
1001
+0.50
+1
0
000
0001
+0.25
+0
0
000
0000
+0.00
+0
0
000
0000
Diode Fault Alarm
-0.25
+0
0
000
0000
-0.50
+0
0
000
0000
-0.75
-1
1
111
1111
A continuity fault detector at DXP detects whether the
remote diode has an open-circuit condition, short-circuit to GND, or short-circuit DXP-to-DXN condition. At
the beginning of each conversion, the diode fault is
checked and the status byte updated. This fault detector is a simple voltage detector; DXP rising above VCC 1V or falling below DXN + 40mV constitutes a fault condition. Also, if the ADC has an extremely low differential
input voltage, the diode is assumed to be shorted and
a fault occurs. Note that the diode fault isn’t checked
until a conversion is initiated, so immediately after
power-on reset the status byte indicates no fault is present even if the diode path is broken. Any diode fault
will return a +127°C fault reading and cause ALERT to
go low.
-1.00
-1
1
111
1111
-25.00
-25
1
110
0111
-25.50
-26
1
110
0110
-54.75
-55
1
100
1001
-55.00
-55
1
100
1001
-65.00
-65
1
011
1111
-70.00
-65
1
011
1111
_______________________________________________________________________________________
9
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
ALERT Interrupts
The ALERT interrupt output signal is latched and can
only be cleared by reading the Alert Response
address. Interrupts are generated in response to THIGH
and TLOW comparisons, when there is a fault with the
remote diode, or when a high-to-low or low-to-high transition at I/O1 or I/O2 is detected.
The interrupt does not halt automatic conversions; new
temperature data continues to be available over the
SMBus interface after ALERT is asserted. The interrupt
output is open-drain so that devices can share a common interrupt line. The interface responds to the SMBus
Alert Response address, an interrupt pointer returnaddress feature (see the Alert Response Address section).
The ALERT interrupt latch is set when the temperature
exceeds an ALARM threshold. ALERT will not be set
again until the threshold is reprogrammed. This prevents the ALERT latch from being set again during the
interval between reading the Alert Response address
and updating the offending alarm threshold. Note that
this behavior is identical to the MAX1618 but is slightly
different from the MAX1617, which continues to interrupt until the temperature no longer exceeds the alarm
threshold. Note also that if some new alarm condition
occurs, such as crossing the other alarm threshold or
having a GPIO transition, a new interrupt is generated.
ALERT Response Address
The SMBus Alert Response interrupt pointer provides
quick fault identification for simple slave devices that
lack the complex, expensive logic needed to be a bus
master. Upon receiving an ALERT interrupt signal, the
host master can broadcast a receive byte transmission
to the Alert Response slave address (0001100b). Then
any slave device that generated an interrupt attempts
to identify itself by putting its own address on the bus
(Table 2).
The Alert Response can activate several different slave
devices simultaneously, similar to the I 2 C General Call.
If more than one slave attempts to respond, bus arbitration rules apply, and the device with the lower address
code wins. The losing device does not generate an
acknowledge and continues to hold the ALERT line low
until serviced. Successful reading of the alert response
address clears the interrupt latch.
Command Byte Functions
The 8-bit command byte register (Table 3) is the master
index that points to the MAX1669’s other registers. The
register’s POR state is 00000001b, so a receive byte
transmission (a protocol that lacks the command byte)
10
Table 2. Read Format for the Alert
Response Address (0001100b)
BIT
NAME
7 (MSB)
ADD7
6
ADD6
5
ADD5
4
ADD4
3
ADD3
2
ADD2
1
ADD1
0 (LSB)
1
FUNCTION
Provide the MAX1669
slave address
Logic 1
that occurs immediately after POR returns the current
remote temperature data.
One-Shot Conversion
The one-shot command immediately forces a new conversion cycle to begin. In software standby mode
(STBY bit = 1), a new conversion starts, after which the
device returns to standby mode. If a conversion is in
progress when a one-shot command is received, the
command is ignored. If a one-shot command is
received in autoconvert mode (STBY bit = 0) between
conversions, a new conversion begins, the conversion
rate timer is reset, and the next automatic conversion
takes place after a full period.
Configuration Byte Functions
The configuration byte register (Table 4) is used to
mask (disable) interrupts, set the OVERT output polarity, and put the device in software standby mode. Bit 1
of the configuration byte in Table 4 is for factory use
only and must be set to 1 (value at POR). This register’s
contents can be read back over the serial interface.
FAN PWM Frequency and
Duty Factor Control
The fan speed is controlled by the average voltage
applied to the fan. The average voltage is equal to the
product of the motor power-supply voltage and the
duty factor. The duty factor is equal to zero upon startup and it is software controlled. The FAN output frequency is controlled by the PWM frequency register
unless this register’s code is set to 1111b (Table 5). A
PWM frequency code of 1111b puts the FAN output in
DAC mode. For all other codes, the FAN frequency is in
the 20Hz to 160Hz range as shown in Table 5. For the
possible synchronized frequencies, also see Table 5.
The FAN output duty factor is controlled by the FAN
duty factor register unless the PWM frequency code is
______________________________________________________________________________________
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
MAX1669
Table 3. Command Byte Bit Assignments
REGISTER
COMMAND
POR STATE
FUNCTION
00h
N/A
Reserved for future use
RTEMP
01h
N/A
Read latest temperature
RSTAT
02h
N/A
Read status byte (temp flags, I/O_ states)
RCFG
03h
0000 0010b
Read configuration byte
04h
N/A
Reserved for future use
05h
N/A
Reserved for future use
Reserved for future use
06h
N/A
RHI
07h
0111 1111b
Read THIGH limit
RLOW
08h
1100 1001b
Read TLOW limit
WCFG
09h
N/A
Write configuration byte
0Ah
N/A
Reserved for future use
0Bh
N/A
Reserved for future use
0Ch
N/A
Reserved for future use
WHI
0Dh
N/A
Write THIGH limit
WLOW
0Eh
N/A
Write TLOW limit
OSHT
0Fh
N/A
One-shot command. Will execute a single conversion even if the
device is in software standby.
RCRIT
10h
0110 0100b
Read TCRIT limit
RPROT
11h
0000 0000b
Read write-once protection byte
RFREQ
12h
0000 0000b
Read PWM frequency
RDUTY
13h
0000 0000b
Read FAN duty factor
RGPIO
14h
1100 0000b
Read GPIO data
15h
N/A
Reserved for future use
16h
N/A
Reserved for future use
17h
N/A
Reserved for future use
WCRIT
18h
N/A
Write TCRIT limit
WPROT
19h
N/A
Write write-once protection byte
WFREQ
1Ah
N/A
Write PWM frequency
WDUTY
1Bh
N/A
Write FAN duty factor
WGPIO
1Ch
N/A
Write GPIO data
RFU
1Dh-FDh
N/A
Reserved for future use
MFG ID
FEh
Least Sig Byte
0100 1101b
Manufacturing ID code = 4Dh, ASCII code for “M” (for Maxim)
DEV ID
FFh
Least Sig Byte
0000 0101b
Device ID code, specific to MAX1669
ID Codes
______________________________________________________________________________________
11
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
Table 4. Configuration Byte Bit Assignments
BIT
NAME
POR STATE
7
(MSB)
MASK0
0
Masks THIGH, TLOW, and diode fault ALERT interrupts when high. If all three MASK_
bits are set high, ALERT interrupts are totally masked.
6
STBY
0
Standby mode control bit. If high, the device immediately stops converting, forces FAN
low, and enters standby mode. If low, the device continuously autoconverts at a 2Hz rate.
5
POL
0
OVERT pin polarity control:
0 = active low (low when TCRIT is crossed)
1 = active high
4
MASK1
0
Masks I/O1 ALERT interrupts when high. Set MASK1 = 1 and connect a 10k to 100k
pull-up resistor on I/O1 to configure I/O1 as an output.
3
MASK2
0
Masks I/O2 ALERT interrupts when high. Set MASK2 = 1 and connect a 10k to 100k
pull-up resistor on I/O2 to configure I/O2 as an output.
2
FAN ON
0
Enables FAN duty factor override when high.
1
Must be “1”
0
Reserved for future use
1
0
RFU
FUNCTION
Table 5. PWM Frequency Data Byte Bit Assignments (Write Command = 1Ah)
BIT
NAME
POR STATE
FUNCTION
Frequency control bit. F3–F0 are decoded as follows:
F3–F0
Frequency (SYNC = GND)
Synchronized Frequency (SYNC Clocked)
0000b
20Hz
fSYNC/13100
0001b
30Hz
fSYNC/8730
0010b
40Hz
fSYNC/6550
0011b
50Hz
fSYNC/5240
0100b
60Hz
fSYNC/4370
0101b
70Hz
fSYNC/3740
0110b
80Hz
fSYNC/3270
0111b
90Hz
fSYNC/2910
1000b
100Hz
fSYNC/2620
1001b
110Hz
fSYNC/2380
1010b
120Hz
fSYNC/2180
1011b
130Hz
fSYNC/2020
1100b
140Hz
fSYNC/1870
1101b
150Hz
fSYNC/1750
1110b
160Hz
fSYNC/1640
1111b
DAC Mode
7 (MSB)
F3
0
6
F2
0
Frequency control bit
5
F1
0
Frequency control bit
4
F0
0
Frequency control bit
3–0
RFU
0
Reserved for future use
set to 1111b. The FAN duty factor can be selected from
0% to 100% in increments of 6.67%.
FAN Output in DAC Mode
If the PWM frequency register is set to code 1111b, the
DAC is multiplexed to the FAN output and the FAN duty
factor register (Table 6) now controls the DAC output
12
voltage rather than the duty factor. In DAC mode, the
output swing is 0 to 0.94 · VCC (out of 4 bits of resolution). To ensure a smooth transition, make sure that the
FAN duty factor code is 0000b prior to setting the PWM
frequency code for DAC mode (1111b). External circuitry must accept an initial FAN DAC voltage of 0.
______________________________________________________________________________________
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
MAX1669
Table 6. Fan Duty-Factor Data Byte Bit Assignments (Write Command = 1Bh)
BIT
NAME
FUNCTION
NAME
FAN duty-factor control bit. D3–D0 are decoded as follows:
D3–D0
Duty
VOUT (nominal)
0000b
0%
0V
0001b
6.67%
0.0625 · VCC
0010b
13.33%
0.125 · VCC
0011b
20%
0.1875 · VCC
0100b
26.67%
0.25 · VCC
0101b
33.33%
0.3125 · VCC
0110b
40%
0.375 · VCC
0111b
46.67%
0.4375 · VCC
1000b
53.33%
0.5 · VCC
1001b
60%
0.5625 · VCC
1010b
66.67%
0.625 · VCC
1011b
73.33%
0.6875 · VCC
1100b
80%
0.75 · VCC
1101b
86.67%
0.8125 · VCC
1110b
93.33%
0.875 · VCC
1111b
100%
0.9375 · VCC
7 (MSB)
D3
0
6
D2
0
FAN duty-factor control bit
5
D1
0
FAN duty-factor control bit
4
D0
0
FAN duty-factor control bit
3–0
RFU
0
Reserved for future use
MASK_ BITS
S
I/O_ PIN
ALERT
R
DELAY
GPIO DATA_ BITS
ALERT RESPONSE
Figure 4. GPIO Logic Diagram
GPIO Data Register
I/O1 and I/O2 are configured through the GPIO data
register and CONFIG byte register (Table 7 and Table 3).
Upon power-up, the GPIOs are set as inputs. To ensure
the I/Os are configured as inputs, set the state of the
DATA1 and DATA2 bits high within the GPIO data register for I/O1 and I/O2, respectively. Figure 4 shows that
by setting the GPIO DATA_ bits high, the open-drain
FET connected to the I/O_ pins goes high impedance.
Next, clear the MASK1 and MASK2 bits low within the
CONFIG byte register to remove the masks on the
ALERT interrupts for I/O1 and I/O2, respectively.
To use I/O1 or I/O2 as an output, first set the MASK1
and MASK2 bits high, respectively. Setting the MASK_
bits high within the CONFIG byte register masks out the
corresponding I/O ALERT interrupts. Since the internal
FETs are open-drain, a pull-up resistor is required from
I/O_ to VCC. The DATA1 and DATA2 bits within the
GPIO data register directly control the state of the outputs of I/O1 and I/O2, respectively (Figure 4).
______________________________________________________________________________________
13
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
Table 7. GPIO Input/Output Data Byte Bit Assignments
BIT
NAME
POR STATE
FUNCTION
7
(MSB)
DATA1
1
For I/O1 configured as an output (MASK1 bit set high and a pull-up resistor on I/O1),
this bit corresponds to the GPIO DATA1 block in Figure 4 and controls the output state
of I/O1. To configure I/O1 as an input, set this bit high and clear the MASK1 bit low
(Figure 4).
6
DATA2
1
For I/O2 configured as an output (MASK2 bit set high and a pull-up resistor on I/O2 ), this
bit corresponds to the GPIO DATA2 block in Figure 4 and controls the output state of I/O2.
To configure I/O2 as an input, set this bit high and clear the MASK2 bit low (Figure 4).
5–0
RFU
0
Reserved for future use
Table 8. Write-Once Protection Byte Bit Assignments
BIT
NAME
POR STATE
FUNCTION
7
(MSB)
PROT1
0
Write-protects the TCRIT limit threshold register when high.
6
PROT2
0
Write-protects certain bits in the configuration register when high:
- STBY standby-mode control (bit 6)
- POL polarity control (bit 5)
- FAN ON control (bit 2)
5
PROT3
0
Write-protects bit 7 in the GPIO register when high (DATA1).
4
PROT4
0
Write-protects bit 6 in the GPIO register when high (DATA2).
3–0
RFU
0
Reserved for future use
Write-Once Protection
Write-once protection allows the host BIOS code to
configure the MAX1669 and protect against data corruption in the host that might cause spurious writes to
the MAX1669. In particular, write protection allows a
foolproof overtemperature override that forces the fan
on, independent of the host system whether in DAC
mode or PWM mode. The bits in the write-protection
register (Table 8), once set high, cannot be reset low
except by power-on reset.
Having a separate write-protect master register rather
than making the actual registers themselves write once
allows the host to read back and verify each register’s
contents before applying final write protection. Having
individual write-protect control over different registers
allows flexibility in application; for example, the TCRIT
and configuration register could be protected while
leaving one or both GPIO outputs free to be used as
actuators.
Status Byte Functions
The status byte register (Table 9) indicates which (if
any) temperature thresholds have been exceeded. The
14
status byte also indicates changes in GPIO states and
transitions and whether there is a fault in the remote
diode DXP-DXN path. After POR, the normal state of all
the flag bits is 0, assuming none of the alarm conditions are present. Bits 2 to 5 of the status byte are
cleared by any successful read of the status byte. Note
that the ALERT interrupt latch is not automatically
cleared when the status flag bit is cleared.
Manufacturer and Device ID Codes
This code identifies the functional capabilities of a particular device. New devices having enhanced or
reduced software or hardware capabilities must be
assigned a new code. The device ID allows the host
system to interrogate the device to determine its capabilities, and use extra features if they’re available. The
device ID code is 2 bytes, for a total of 256X256 possible combinations. The device ID codes are located at
command code 1111 1111b (FFh). If a read-byte operation (as opposed to a read-word) is applied to the
device, it returns the least-significant byte correctly
without the most-significant byte. Table 10 shows the
device ID code for the MAX1669.
______________________________________________________________________________________
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
MAX1669
Table 9. Status Byte Bit Assignments
BIT
NAME
FUNCTION
7
(MSB)
I/O1
This bit indicates the current state of I/O1 (unlatched).
6
I/O2
This bit indicates the current state of I/O2 (unlatched).
5
TRAN1*
This bit is set if a low-to-high or high-to-low transition has occurred at I/O1 (regardless of the
state of the mask bits).
4
TRAN2*
This bit is set if a low-to-high or high-to-low transition has occurred at I/O2 (regardless of the
state of the mask bits).
3
RHIGH*
A high indicates that the high-temperature alarm has activated
2
RLOW*
A high indicates that the low-temperature alarm has activated.
1
DIODE
A high indicates a remote-diode fault (open-circuit, shorted diode, or DXP short to GND).
0 (LSB)
OVERT
When the TCRIT threshold is crossed, this bit goes high. The polarity of this bit does not depend
on the POL bit (bit 5 in configuration byte).
*TRAN1 and TRAN2 alarm flags stay high until cleared by POR or until the status byte register is read. RHIGH and RLOW alarm
flags stay high until cleared by POR or the temperature fault is removed and the status byte is read.
Slave Addresses
Table 10. Device ID Code
MAX1669 ID CODE
LS BYTE
LSBs MSBs
MS BYTE
LSBs MSBs
0000 0101
0000 0000
Table 11. Slave Address Decoding
(ADD_ Pins)
ADD0
ADD1
ADD2
ADDRESS
GND
GND
GND
0011 000b
GND
GND
VCC
0011 001b
GND
VCC
GND
0011 010b
GND
VCC
VCC
0101 001b
VCC
GND
GND
0101 010b
VCC
GND
VCC
0101 011b
VCC
VCC
GND
1001 100b
VCC
VCC
VCC
1001 101b
The MAX1669 appears to the SMBus as one device
having a common address for the temperature sensor
section, GPIO section, and fan-control section. The
device address can be set to one of eight different values by pin-strapping ADD_ pins so that more than one
MAX1669 can reside on the same bus without address
conflicts (Table 11).
The MAX1669 also responds to the SMBus Alert
Response slave address (see the Alert Response
Address section).
POR and UVLO
The MAX1669’s memory is volatile. To prevent ambiguous power-supply conditions from corrupting the data
in memory and causing erratic behavior, a POR voltage
detector monitors VCC and clears the memory if VCC
falls below 1.85V (typical, see the Electrical Characteristics table). When power is first applied and VCC rises
above 1.9V (typ), the logic blocks begin operating;
although reads and writes at VCC levels below 3V are
not recommended. A second V CC comparator, the
ADC UVLO comparator, prevents the ADC from converting until there is sufficient headroom (VCC = 2.8V typ).
______________________________________________________________________________________
15
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
Power-Up Defaults
• Interrupt latch is cleared.
• ADC begins autoconverting at a 2Hz rate.
• Command byte is set to 01h to facilitate quick
remote receive-byte queries.
• THIGH and TLOW registers are set to +127°C and
-55°C limits, respectively.
• TCRIT register is set to +100°C.
• ALERT and OVERT are reset to high-Z state.
• Device is in low-frequency PWM mode, 20Hz setting.
• PWM output is off (duty factor set to 0%).
• I/O1, I/O2 are high-Z (configured as inputs).
Table 12. Component Manufacturers
MANUFACTURER
MODEL NUMBER
SOT23 BJT
Central Semiconductor (USA)
CMPT3906
Fairchild Semiconductor (USA)
MMBT3906
Motorola (USA)
MMBT3906
Rohm Semiconductor (Japan)
SST3906
Samsung (Korea)
KST3906
MOSFET N-CHANNEL
International Rectifier (USA)
__________Applications Information
Remote Diode Selection
Temperature accuracy depends on having a goodquality, diode-connected, small-signal transistor.
Accuracy has been experimentally verified for all of the
devices listed in Table 12. The MAX1669 can also
directly measure the die temperature of CPUs and
other ICs having on-board temperature-sensing diodes,
such as the Intel Pentium II.
The transistor must be a small-signal type having a relatively high forward voltage; otherwise, the A/D input
voltage range can be violated. The forward voltage
must be greater than 0.25V at 10µA; check to ensure
this is true at the highest expected temperature. The
forward voltage must be <0.95V at 100µA; check to
ensure this is true at the lowest expected temperature.
Do not use large power transistors. Also, ensure that
the base resistance is <100Ω. Tight specifications for
forward-current gain (+50 to +150, for example) indicate that the manufacturer has good process controls
and the devices have consistent VBE characteristics.
Series resistance causes +1/2°C error per ohm. When
monitoring the temperature of a remote unit’s internal
diode, ensure that trace series resistance does not
introduce significant error.
ADC Noise Filtering
The ADC is an integrating type with inherently good
noise rejection, especially of low-frequency signals
such as 60Hz/120Hz power-supply hum. Micropower
operation places constraints on high-frequency noise
rejection; therefore, careful PC board layout and proper
external noise filtering is required for high-accuracy
16
Fairchild Semiconductor (USA)
IRF7201
FDN359AN
MOSFET P-CHANNEL
International Rectifier (USA)
IRF7205
Note: Transistors must be diode-connected (base shorted to
collector).
remote measurements in electrically noisy environments.
High-frequency EMI is best filtered at DXP and DXN
with an external 2200pF capacitor. This value can be
increased to about 3300pF (max), including cable
capacitance. Capacitance higher than 3300pF introduces errors due to the rise time of the switched-current source.
Nearly all noise sources tested cause the ADC measurements to be higher than the actual temperature,
typically by +1°C to +10°C, depending on frequency
and amplitude (see Typical Operating Characteristics).
FAN Application Circuits
In PWM mode, the output impedance at FAN is <50Ω,
enabling it to drive an N-channel MOSFET as shown in
the Typical Operating Circuit. Return the source of the
N-channel MOSFET to the system power ground, away
from the ground of the MAX1669. For 3.3V applications,
use low-threshold N-channel MOSFETs (Table 1).
In DAC mode, the FAN output can be linearly controlled
(Figure 5). Upon power-up, the fan is off. The N-channel
MOSFET is biased at the threshold of turning on. As
VFAN rises, the fan turns on linearly. To have the fan
turned on at power-up, use the circuit shown in Figure 6.
______________________________________________________________________________________
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
MAX1669
+5V
10k
10k
10k
0.1µF
10k
+12V
SMBCLK
VCC
SMBDATA
ALERT
OVERT
2N3906
DXP
100k
2200pF
MAX1669
38k
N-CH
IRF7201
FAN
DXN
SYNC
ADD0
I/O1
ADD1
I/O2
38k
ADD2
AGND
PGND
SYSTEM POWER
GROUND
Figure 5. Linear Fan Control (DAC Mode) with Fan “Off” at Power-Up
+5V
10k
10k
10k
0.1µF
10k
SMBCLK
+12V
VCC
SMBDATA
ALERT
22k
OVERT
33k
P-CH
IRF7205
FAN
2N3906
DXP
2200pF
5.1V
ZENER
MAX1669
100k
DXN
SYNC
ADD0
I/O1
ADD1
I/O2
ADD2
AGND
PGND
SYSTEM POWER
GROUND
Figure 6. Linear Fan Control (DAC Mode) with Fan “On” at Power-Up
______________________________________________________________________________________
17
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
Typical Operating Circuit
A
B
tLOW
C
D
F
E
G
H
J
I
tHIGH
K
SMBCLK
SMBDATA
tSU:STA tHD:STA
tSU:STO
tSU:DAT
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
tBUF
I = ACKNOWLEDGE CLOCK PULSE
J = STOP CONDITION
K = NEW START CONDITION
Figure 7. SMBus Write Timing Diagram
A
tLOW
B
tHIGH
C
D
E
F
G
H
I
J
K
L
M
SMBCLK
SMBDATA
tSU:STA
tHD:STA
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
tSU:DAT
tHD:DAT
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS SMBDATA LINE LOW
tSU:STO tBUF
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
Figure 8. SMBus Read Timing Diagram
18
______________________________________________________________________________________
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
+3V TO +5.5V
10k
10k
10k
0.1µF
10k
SMBCLK
VCC
SMBDATA
+12V
ALERT
OVERT
2N3906
DXP
2200pF
MAX1669
DXN
FAN
N-CH
FDN 359AN
SYNC
ADD0
I/O1
ADD1
I/O2
ADD2
AGND
SYSTEM POWER
GROUND
PGND
Chip Information
TRANSISTOR COUNT: 12,924
______________________________________________________________________________________
19
MAX1669
Typical Operating Circuit
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
QSOP.EPS
MAX1669
Package Information
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
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