19-3713; Rev 2; 10/08
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
The MAX6615/MAX6616 monitor two temperature channels, either the internal die temperature and the temperature of an external thermistor, or the temperatures of
two external thermistors. The temperature 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 maximum cooling when power
dissipation increases. The fans’ tachometer output signals are monitored by the MAX6615/MAX6616 to detect
fan failure. If a fan failure is detected, the FAN_FAIL
output is asserted.
The 2-wire serial interface accepts standard system
management bus (SMBus TM) write byte, read byte,
send byte, and receive byte commands to read the
temperature data and program the alarm thresholds.
The programmable alarm output can be used to generate interrupts, throttle signals, or overtemperature shutdown signals.
The MAX6616 features six GPIOs to provide additional
flexibility. All of the GPIOs power-up as inputs, with the
exception of GPIO0, which powers up as either an input
or an output as determined by connecting the PRESET
pin to ground or VCC.
The MAX6616 is available in a 24-pin QSOP package,
while the MAX6615 is available in a 16-pin QSOP package. Both devices operate from a single-supply voltage
range of 3.0V to 5.5V, have operating temperature
ranges of -40°C to +125°C, and consume just 500µA of
supply current.
Features
o Two Thermistor Inputs
o Two Open-Drain PWM Outputs for Fan-Speed
Control
o Local Temperature Sensor
o Six GPIOs (MAX6616)
o Programmable Fan-Control Characteristics
o Controlled PWM Rate-of-Change Ensures
Unobtrusive Fan-Speed Adjustments
o Fail-Safe System Protection
o OT Output for Throttling or Shutdown
o Nine Different Pin-Programmable SMBus
Addresses
o 16-Pin and 24-Pin QSOP Packages
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX6615AEE
-40°C to +125°C
16 QSOP
MAX6616AEG
-40°C to +125°C
24 QSOP
Functional Diagram
FAN_FAIL
Applications
VCC
Desktop Computers
Servers
TH1
Power Supplies
REF
Networking Equipment
TH2
THERMISTORS
AND LOCAL
TEMP SENSOR
PWM
GENERATOR
AND TACH
COUNTER
TACH1
PWM1
TACH2
PWM2
Workstations
SCL
SMBus is a trademark of Intel Corp.
SDA
Typical Application Circuits and Pin Configurations appear at
end of data sheet.
SMBus
INTERFACE
AND
REGISTERS
OT
LOGIC
GPIO0*
GPIO5*
PRESET*
MAX6615
MAX6616
GND
ADD0
ADD1
*MAX6616 ONLY
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
MAX6615/MAX6616
General Description
MAX6615/MAX6616
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
ABSOLUTE MAXIMUM RATINGS
All Voltages Are Referenced to GND
Supply Voltage (VCC) ...............................................-0.3V to +6V
PWM_, TACH_, OT, FAN_FAIL ............................-0.3V to +13.5V
ADD0, ADD1, SDA, SCL ..........................................-0.3V to +6V
All Other Pins..............................................-0.3V to (VCC + 0.3V)
SDA, OT, FAN_FAIL, PWM_, GPIO_ Current....................±50mA
TH_ Current ........................................................................±1mA
REF Current ......................................................................±20mA
Continuous Power Dissipation (TA = +70°C)
16-Pin QSOP (derated at 8.3mW/°C
above +70°C)............................................................666.7mW
24-Pin QSOP (derated at 9.5mW/°C
above +70°C)...........................................................761.9 mW
ESD Protection (all pins, Human Body Model) ....................±2kV
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
(VCC = +3.0V to +5.5V, TA= 0°C to +125°C, unless otherwise noted. Typical values are at VCC = +3.3V, TA = +25°C.)
PARAMETER
Operating Supply Voltage
SYMBOL
MIN
TYP
3.0
VCC
Standby Current
Operating Current
CONDITIONS
Interface inactive, ADC in idle state
IS
Interface inactive, ADC active
0.5
VCC = +3.3V, 0.15V ≤ VTH_ ≤ +0.71V (excludes
thermistor errors, thermistor nonlinearity) (Note1)
External Temperature Error
Internal Temperature Error
MAX
5.5
V
10
µA
1
mA
±1
°C
VCC = +3.3V, 0°C ≤ TA ≤ +85°C,
±2.5
VCC = +3.3V, 0°C ≤ TA ≤ +125°C
±4
Temperature Resolution
0.125
Conversion Time
UNITS
°C
°C
250
ms
Conversion Rate Timing Error
-20
+20
%
PWM Frequency Error
-20
+20
%
INPUT/OUTPUT
Output Low Voltage
VOL
Output High Leakage Current
IOH
Logic Low Input Voltage
VIL
Logic High Input Voltage
VIH
VCC = +3V, IOUT = 6mA
V
1
µA
0.8
2.1
1
CIN
V
V
Input Leakage Current
Input Capacitance
0.4
5
µA
pF
SMBus TIMING (Figures 2, 3) (Note 2)
Serial Clock Frequency
fSCLK
10
400
kHz
Clock Low Period
tLOW
10% to 10%
4
µs
Clock High Period
tHIGH
90% to 90%
4.7
µs
Bus Free Time Between STOP
and START Conditions
tBUF
4.7
µs
4.7
µs
SMBus START Condition
Setup Time
2
tSU:STA
90% of SCL to 90% of SDA
_______________________________________________________________________________________
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
(VCC = +3.0V to +5.5V, TA= 0°C to +125°C, unless otherwise noted. Typical values are at VCC = +3.3V, TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
START Condition Hold Time
tHD:STO
10% of SDA to 10% of SCL
STOP Condition Setup Time
tSU:STO
Data Setup Time
tSU:DAT
Data Hold Time
tHD:DAT
MIN
TYP
MAX
UNITS
4
µs
90% of SCL to 10% of SDA
4
µs
10% of SDA to 10% of SCL
250
ns
10% of SCL to 10% of SDA
300
ns
SMBus Fall Time
tF
300
ns
SMBus Rise Time
tR
1000
ns
55
ms
SMBus Timeout
(Note 3)
29
37
Note 1: 1°C of error corresponds to an ADC error of 7.76mV when VREF = 1V.
Note 2: Guaranteed by design and characterization.
Note 3: Production tested.
Typical Operating Characteristics
(VCC = +3.3V, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
REMOTE
100
10
SHUTDOWN
100
80
60
40
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
5.0
5.5
1
0
-1
20
0
1
2
MAX6615/6 toc03
MAX6615/6 toc02
120
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
TEMPERATURE ERROR (°C)
SUPPLY CURRENT (µA)
LOCAL
THERMISTOR TEMPERATURE DATA (°C)
MAX6615/6 toc01
1000
THERMISTOR TEMPERATURE DATA
vs. THERMISTOR TEMPERATURE
-2
0
20
40
60
80
100
THERMISTOR TEMPERATURE (°C)
120
0
25
50
75
100
DIE TEMPERATURE (°C)
_______________________________________________________________________________________
3
MAX6615/MAX6616
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics (continued)
(VCC = +3.3V, TA = +25°C, unless otherwise noted.)
GPIO OUTPUT VOLTAGE
vs. GPIO SINK CURRENT
40
0.8
0.7
VGPIO_ = 0.4V
VCC = 3V
VGPIO_ (V)
0.6
35
30
0.5
0.4
VCC = 5V
0.3
25
0.2
20
0.1
15
0
3.0
3.5
4.0
4.5
5.0
3
2
1
0
-1
-2
-3
-4
0
5.5
4
FREQUENCY SHIFT (Hz)
45
5
MAX6615/6 toc05
0.9
MAX6615/6 toc04
50
PWM FREQUENCY
vs. DIE TEMPERATURE
MAX6615/6 toc06
GPIO SINK CURRENT
vs. SUPPLY VOLTAGE
IGPIO_ (mA)
10
20
30
40
50
60
80
70
IGPIO_ (mA)
VCC (V)
NORMALIZED AT TA = +25°C
-5
0
25
50
MAX6615/6 toc07
0.10
0.08
0.06
0.04
0.02
0
-0.02
NORMALIZED AT VCC = 5.0V
-0.04
3.0
3.5
4.0
4.5
5.0
5.5
VCC (V)
4
75
DIE TEMPERATURE (°C)
PWM FREQUENCY
vs. SUPPLY VOLTAGE
FREQUENCY SHIFT (Hz)
MAX6615/MAX6616
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
_______________________________________________________________________________________
100
125
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
PIN
NAME
FUNCTION
MAX6616
MAX6615
1, 2, 5, 20,
23, 24
—
GPIO0–
GPIO5
3
1
PWM1
Fan Driver Output 1. The pullup resistor can be connected to a supply voltage as high as
12V, regardless of the supply voltage. See the PWM Output section for configuration.
4
2
TACH1
Fan Tachometer Input. Accepts logic-level signal from fan’s tachometer output. Can be
connected to a supply voltage as high as 12V, regardless of the supply voltage.
6
3
ADD0
SMBus Slave Address Selection
7
4
ADD1
SMBus Slave Address Selection
8
5, 10
GND
Ground. Must be connected together for MAX6615.
Active-Low, Open-Drain GPIOs. Can be pulled up to 5.5V regardless of VCC.
9
6
TH1
External Thermistor Input 1. Connect a thermistor in series with a fixed resistor between
REF and ground.
10, 15
—
N.C.
No Connection
11
7
REF
Reference Voltage Output. Provides 1V during measurements. High impedance when not
measuring.
12
8
TH2
External Thermistor Input 2. Connect a thermistor in series with a fixed resistor between
REF and ground.
13
9
FAN_FAIL
Fan-Failure Output. Asserts low when either fan fails. Can be pulled up as high as 5.5V
regardless of VCC. High impedance when VCC = 0V.
14
—
PRESET
Connect to GND or VCC to set POR state of the GPIO0.
16
11
OT
Overtemperature Output. Active low, open drain. Typically used for system shutdown or
clock throttling. Can be pulled up as high as 5.5V regardless of VCC. High impedance
when VCC = 0V.
17
12
VCC
Power Supply. 3.3V nominal. Bypass with a 0.1µF capacitor to GND.
18
13
SDA
SMBus Serial-Data Input/Output. Pull up with a 10kΩ resistor. Can be pulled up as high
as 5.5V regardless of VCC. High impedance when VCC = 0V.
19
14
SCL
SMBus Serial-Clock Input. Pull up with a 10kΩ resistor. Can be pulled up as high as 5.5V
regardless of VCC. High impedance when VCC = 0V.
21
15
TACH2
Fan Tachometer Input. Accepts logic-level signal from fan’s tachometer output. Can be
connected to a supply voltage as high as 12V, regardless of the supply voltage.
22
16
PWM2
Fan Driver Output 2. The pullup resistor can be connected to a supply voltage as high as
12V, regardless of the supply voltage. See the PWM Output section for configuration.
_______________________________________________________________________________________
5
MAX6615/MAX6616
Pin Description
MAX6615/MAX6616
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
WRITE BYTE FORMAT
S
—
ADDRESS
WR
ACK
7 BITS
—
—
SLAVE ADDRESS: EQUIVALENT TO CHIP-SELECT LINE
OF A 3-WIRE INTERFACE
COMMAND
ACK
8 BITS
—
COMMAND BYTE: SELECTS
WHICH REGISTER YOU ARE
WRITING TO
DATA
ACK
P
8 BITS
—
1
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
7 BITS
—
—
SLAVE ADDRESS:
EQUIVALENT TO CHIPSELECT LINE
SEND BYTE FORMAT
COMMAND
ACK
S
8 BITS
—
—
COMMAND BYTE:
SELECTS WHICH
REGISTER YOU ARE
READING FROM
ADDRESS
RD
ACK
7 BITS
—
—
SLAVE ADDRESS: REPEATED DUE TO CHANGE IN
DATA- FLOW DIRECTION
RECEIVE BYTE FORMAT
DATA
///
P
8 BITS
—
—
DATA BYTE: READS
FROM THE REGISTER
SET BY THE COMMAND
BYTE
S
ADDRESS
WR
ACK
COMMAND
ACK
P
S
ADDRESS
RD
ACK
DATA
///
P
—
7 BITS
—
—
8 BITS
—
—
—
7 BITS
—
—
8 BITS
—
—
COMMAND BYTE: SENDS COMMAND WITH NO DATA, USUALLY
USED FOR ONE-SHOT COMMAND
S = START CONDITION
P = STOP CONDITION
SHADED = SLAVE TRANSMISSION
/// = NOT ACKNOWLEDGED
DATA BYTE: READS DATA FROM
THE REGISTER COMMANDED BY
THE LAST READ BYTE OR WRITE
BYTE TRANSMISSION; ALSO
USED FOR SMBUS ALERT
RESPONSE RETURN ADDRESS
Figure 1. SMBus Protocols
Detailed Description
The MAX6615/MAX6616 accurately monitor two temperature channels, either the internal die temperature
and the temperature of an external thermistor, or the
temperatures of two external thermistors. They report
temperature values in digital form using a 2-wire
SMBus/I2C-compatible serial interface. The MAX6615/
MAX6616 operate from a supply voltage range of 3.0V
to 5.5V and consume 500µA (typ) of supply current.
The temperature data controls the duty cycles of two
PWM output signals that are used to adjust the speed
of a cooling fan. They also feature an overtemperature
alarm output to generate interrupts, throttle signals, or
shutdown signals.
The MAX6616 also includes six GPIO input/outputs to
provide additional flexibility. The GPIO0 power-up state
is set by connecting the GPIO PRESET input to ground
or VCC.
have nine different slave addresses available; therefore, a
maximum of nine MAX6615/MAX6616 devices can share
the same bus.
The MAX6615/MAX6616 employ four standard SMBus
protocols: write byte, read byte, send byte, and receive
byte (Figures 1, 2, and 3). The shorter receive byte protocol allows quicker transfers, provided that the correct
data register was previously selected by a 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.
Temperature data can be read from registers 00h and
01h. The temperature data format for these registers is
8 bits, with the LSB representing 1°C (Table 1) and the
MSB representing 128°C. The MSB is transmitted first.
All values below 0°C clip to 00h.
Table 3 details the register address and function, whether
they can be read or written to, and the power-on reset
SMBus Digital Interface
From a software perspective, the MAX6615/MAX6616
appear as a set of byte-wide registers. Their devices use
a standard SMBus 2-wire/I2C-compatible serial interface
to access the internal registers. The MAX6615/MAX6616
6
_______________________________________________________________________________________
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
B
tLOW
C
D
F
E
G
H
tHIGH
I
J
K
L
MAX6615/MAX6616
A
M
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 SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
tBUF
I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
Figure 2. 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 MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = MASTER PULLS DATA LINE LOW
tSU:STO tBUF
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
Figure 3. SMBus Read Timing Diagram
(POR) state. See Tables 3–7 for all other register functions
and the Register Descriptions section.
Temperature Measurements
The averaging ADC integrates over a 120ms period
(each channel, typically), with excellent noise rejection.
For internal temperature measurements, the ADC and
associated circuitry measure the forward voltage of the
internal sensing diode at low- and high-current levels
and compute the temperature based on this voltage.
For thermistor measurements, the reference voltage
and the thermistor voltage are measured and offset is
applied to yield a value that correlates well to thermistor
temperature within a wide temperature range. Both
channels are automatically converted once the conversion process has started. If one of the two channels is
not used, the circuit still performs both measurements,
and the data from the unused channel may be ignored.
If either of the measured temperature values is below
0°, the value in the corresponding temperature register
is clipped to zero when a negative offset is programmed into the thermistor offset register (17h).
Local (internal) temperature data is expressed directly
in degrees Celsius. Two registers contain the temperature data for the local channel. The high-byte register
has an MSB of 128°C and an LSB of 1°C. The low- byte
register contains 3 bits, with an MSB of 0.5°C and an
LSB of 0.125°C. The data format is shown in Table 1.
Thermistors allow measurements of external temperatures. Connect a thermistor in series with a resistor,
REXT. The thermistor should be connected between the
TH_ input and ground, and REXT should be connected
between the reference output, REF, and the TH_ input,
as shown in the Typical Application Circuit.
The voltage across R EXT is measured by the ADC,
resulting in a value that is directly related to tempera-
_______________________________________________________________________________________
7
MAX6615/MAX6616
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
Table 1. Temperature Data Format (High Byte and Low Byte)
TEMPERATURE (°C)
140.0
HIGH BYTE
BINARY VALUE
HEX VALUE
BINARY VALUE
HEX VALUE
1000 1100
8Ch
0000 0000
00h
127.0
0111 1111
7Fh
0000 0000
00h
25.375
0001 1001
19h
0110 0000
60h
25.0
0001 1001
19h
0000 0000
00h
0.5
0000 0000
00h
1000 0000
80h
0.0
0000 0000
00h
0000 0000
00h
FanStartTemperature:
DC = FSDC + (T - FST) ×
VCC
5V
4.7kΩ
PWM
DCSS
TS
where:
DC = DutyCycle
FSDC = FanStartDutyCycle
T = Temperature
FST = FanStartTemperature
DCSS = DutyCycleStepSize
TS = TempStep
Figure 6. Controlling a PWM Input Fan with the MAX6615/
MAX6616s’ PWM Output (Typically, the 35kHz PWM
Frequency Is Used)
brushless DC motor has enough time to operate. When
driving a fan with a PWM-to-DC circuit as shown in
Figure 5, the highest available frequency (35kHz) should
be used to minimize the size of the filter capacitors.
When using a fan with a PWM control input, the frequency normally should be high as well, although some fans
have PWM inputs that accept low-frequency drive.
The duty cycle of the PWM can be controlled in two ways:
1) Manual PWM control: setting the duty cycle of the fan
directly through the fan target duty-cycle registers
(0Bh and 0Ch).
2) Automatic PWM control: setting the duty cycle based
on temperature.
Manual PWM Duty-Cycle Control
Clearing the bits that select the temperature channels for
fan control (D5 and D4 for PWM1 and D3 and D2 for
PWM2) in the fan-configuration register (11h) enables
manual fan control. In this mode, the duty cycle written to
the fan target duty-cycle register directly controls the
Duty cycle is recalculated after each temperature conversion if temperature is increasing. If the temperature
begins to decrease, the duty cycle is not recalculated
until the temperature drops by 5°C from the last peak
temperature. The duty cycle remains the same until the
temperature drops 5°C from the last peak temperature or
the temperature rises above the last peak temperature.
For example, if the temperature goes up to +85°C and
starts decreasing, duty cycle is not recalculated until the
temperature reaches +80°C or the temperature rises
above +85°C. If the temperature decreases further, the
duty cycle is not updated until it reaches +75°C.
For temperature < FanStartTemperature and D2 of
configuration register = 0:
DutyCycle = 0
For temperature < FanStartTemperature and D2 of
configuration register = 1:
DutyCycle = FanStartDutyCycle
Once the temperature crosses the fan-start temperature
threshold, the temperature has to drop below the fanstart temperature threshold minus the hysteresis before
_______________________________________________________________________________________
9
MAX6615/MAX6616
+12V
MAX6615/MAX6616
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
Fan-Fail
DUTY CYCLE
REGISTER 02h,
BIT D3 = 1
DUTY-CYCLE
STEP SIZE
FAN-START
DUTY CYCLE
TEMP
STEP
REGISTER 02h,
BIT D3 = 0
TEMPERATURE
FAN-START
TEMPERATURE
When the fan tachometer count is larger than the fan
tachometer limit, the fan is considered failing. The
MAX6615/MAX6616 PWM_ drives the fan with 100%
duty cycle for about 2s immediately after detecting a
fan-fail. At the end of that period, another measurement
is initiated. If the fan fails both measurements, the
FAN_FAIL bit, as well as the FAN_FAIL output, assert if
the pin is not masked. If the fan fails only the first measurement, the fan goes back to normal settings.
If one fan fails, it can be useful to drive the other fan
with 100% duty cycle. This can be enabled with bit D0
of the fan-status register (1Ch).
Slave Addresses
Figure 7. Automatic PWM Duty Control
the duty cycle returns to either 0% or the fan-start duty
cycle. The value of the hysteresis is set by D7 of the
fan-configuration register.
The duty cycle is limited to the value in the fan maximum
duty-cycle register. If the duty-cycle value is larger than
the maximum fan duty cycle, it is set to the maximum
fan-duty cycle as in the fan maximum duty-cycle register.
The temperature step is bit D6 of the fan-configuration
register (0Dh).
The MAX6615/MAX6616 appear to the SMBus as one
device having a common address for both ADC channels. The devices’ address can be set to one of nine
different values by pinstrapping ADD0 and ADD1 so
that more than one MAX6615/MAX6616 can reside on
the same bus without address conflicts (see Table 2).
The address input states are checked regularly, and
the address data stays latched to reduce quiescent
supply current due to the bias current needed for highimpedance state detection.
Power-On Defaults
Notice if temperature crosses FanStartTemperature
going up with an initial DutyCycle of zero, a spin-up of
2s applies before the duty-cycle calculation controls
the value of the fan’s duty cycle.
At power-on, or when the POR bit in the configuration
byte register is set, the MAX6615/MAX6616 have the
default settings indicated in Table 3. Some of these settings are summarized below:
FanStartTemperature for a particular channel follows the
channel, not the fan. If DutyCycle is an odd number, it is
automatically rounded down to the closest even number.
•
Temperature conversions are active.
•
Channel 1 and channel 2 are set to report the
remote temperature channel measurements.
Duty-Cycle Rate-of-Change Control
To reduce the audibility of changes in fan speed, the
rate of change of the duty cycle is limited by the values
set in the duty-cycle rate-of-change register. Whenever
the target duty cycle is different from the instantaneous
duty cycle, the duty cycle increases or decreases at
the rate determined by the duty-cycle rate-of-change
byte until it reaches the target duty cycle. By setting the
rate of change to the appropriate value, the thermal
requirements of the system can be balanced against
good acoustic performance. Slower rates of change
are less noticeable to the user, while faster rates of
change can help minimize temperature variations.
Remember that the fan controller is part of a complex
control system. Because several of the parameters are
generally not known, some experimentation may be
necessary to arrive at the best settings.
•
Channel 1 OT limit = +110°C.
•
Channel 2 OT limit = +80°C.
•
Manual fan mode.
•
Fan-start duty cycle = 0.
•
PWM invert bit = 1.
10
______________________________________________________________________________________
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
ADDO
ADD1
ADDRESS
GND
GND
0011 000
GND
High-Impedance
GND
VCC
0011 010
GND
0101 001
High-Impedance
0011 001
High-Impedance
High-Impedance
0101 010
High-Impedance
VCC
0101 011
GND
1001 100
VCC
VCC
High-Impedance
1001 101
VCC
VCC
1001 110
Note: High-Impedance means that the pin is left unconnected
and floating.
GPIO Inputs/Outputs and
Preset (MAX6616)
The MAX6616 has six GPIO ports. GPIO0 has a POR
control pin (PRESET). When PRESET is connected to
GND at POR, GPIO0 is configured as an output and is
low. When PRESET is connected to VCC at POR, GPIO0
is configured as an input. Since GPIO0 is a highimpedance node in this state, it can be connected to a
pullup resistor and also serve as an output (high). The
rest of the GPIO ports, GPIO5–GPIO1, are configured
as high-impedance outputs after power-on, so they will
be in the high state if connected to pullup resistors. All
GPIOs are at their preset values within 1ms of powerup. During power-up, GPIO1 and GPIO2 are low while
the remaining GPIOs go into high-impedance state.
Figure 8 shows the states of the GPIO lines during
power-up. After power has been applied to the
MAX6616, the GPIO functions can be changed through
the SMBus interface.
VCC
POR (INTERNAL)
STATE DETERMINED BY
PRESET
GPIO0
GPIO1, GPIO2
HIGH-IMPEDANCE STATE
GPIO3, GPIO4,
GPIO5
HIGH-IMPEDANCE STATE
1ms
Figure 8. Power-On GPIO States
Register Descriptions
The MAX6615/MAX6616 contain 32/34 internal registers. These registers store temperature data, allow control of the PWM outputs, determine if the devices are
measuring from the internal die or the thermistor inputs,
and set the GPIO as inputs or outputs.
Temperature Registers (00h and 01h)
The temperature registers contain the results of temperature measurements. The value of the MSB is 128°C and
the value of the LSB is 1°C. Temperature data for thermistor channel 1 is in the temperature channel 1 register
(00h). Temperature data for thermistor channel 2 (01h)
or the local sensor (selectable by bit D2 in the configuration byte) is in the temperature channel 2 register.
Configuration Byte (02h)
The configuration byte register controls timeout conditions and various PWM signals. The POR state of the
configuration byte register is 18h. See Table 4 for configuration byte definitions.
Channel 1 and Channel 2 OT Limits (03h and 04h)
Set channel 1 (03h) and channel 2 (04h) temperature
thresholds with these two registers. Once the temperature
is above the threshold, the OT output is asserted low (for
the temperature channels that are not masked). The POR
state of the channel 1 OT limit register is 6Eh, and the
POR state of the channel 2 OT limit register is 50h.
OT Status (05h)
A 1 in D7 or D6 indicates that an OT fault has occurred
in the corresponding temperature channel. Only reading its contents clears this register. Reading the contents of the register also clears the OT output. If the
fault is still present on the next temperature measurement cycle, the bits and the OT output are set again.
The POR state of the OT status register is 00h.
OT Mask (06h)
Set bit D7 to 1 in the OT mask register to prevent the
OT output from asserting on faults in channel 1. Set bit
D6 to 1 to prevent the OT output from asserting on
faults in channel 2. The POR state of the OT mask register is 00h.
PWM Start Duty Cycle (07h and 08h)
The PWM start duty-cycle register determines the PWM
duty cycle where the fan starts spinning. Bit D2 in the
configuration byte register (MIN DUTY CYCLE) determines the starting duty cycle. If the MIN DUTY CYCLE
bit is 1, the duty cycle is the value written to the fanstart duty-cycle register at all temperatures below the
fan-start temperature. If the MIN DUTY CYCLE bit is
______________________________________________________________________________________
11
MAX6615/MAX6616
Table 2. Slave Address Decoding (ADD0
and ADD1)
MAX6615/MAX6616
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
Table 3. Register Map
R/W ADD
POR
STATE
FUNCTION
D7
D6
D5
D4
D3
D2
D1
D0
R
00h
0000
0000
Temperature
channel 1
MSB
(128°C)
—
—
—
—
—
—
LSB (1°C)
R
01h
0000
0000
Temperature
channel 2
MSB
(128°C)
—
—
—
—
—
—
LSB (1°C)
POR:
1 = reset
Timeout:
0=
enabled;
1=
disabled
Fan 1
PWM
invert
Fan 2
PWM
invert
Min duty
cycle: 0 =
0%; 1 =
fan-start
duty
cycle
Temp
Ch2
sources:
1 = local;
0=
remote2
Spin-up
disable: 0
= enable;
1=
disable
R/W
02h
0001
1000
Configuration
byte
Standby:
0 = run;
1=
standby
R/W
03h
0110
1110
Temperature
channel 1
OT limit
MSB
—
—
—
—
—
—
LSB (1°C)
R/W
04h
0101
0000
Temperature
channel 2
OT limit
MSB
—
—
—
—
—
—
LSB (1°C)
R
05h
00xx
xxxx
OT status
Channel 1:
1 = fault
Channel
2: 1 =
fault
—
—
—
—
—
—
R/W
06h
00xx
xxxx
OT mask
Channel 1:
1=
masked
Channel
2: 1 =
masked
—
—
—
—
—
—
07h
0110
000x
96 =
40%
PWM1 start
duty cycle
MSB
(128/240)
—
—
—
—
—
LSB
(2/240)
—
08h
0110
000x
96 =
40%
PWM2 start
duty cycle
MSB
(128/240)
—
—
—
—
—
LSB
(2/240)
—
09h
1111
000x
240 =
100%
PWM1 max
duty cycle
MSB
(128/240)
—
—
—
—
—
LSB
(2/240)
—
R/W
0Ah
1111
000x
240 =
100%
PWM2 max
duty cycle
MSB
(128/240)
—
—
—
—
—
LSB
(2/240)
—
R/W
0Bh
0000
000x
PWM1 target
duty cycle
MSB
(128/240)
—
—
—
—
—
LSB
(2/240)
—
R/W
0Ch
0000
000x
PWM2 target
duty cycle
MSB
(128/240)
—
—
—
—
—
LSB
(2/240)
—
R/W
R/W
R/W
12
______________________________________________________________________________________
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
MAX6615/MAX6616
Table 3. Register Map (continued)
POR
STATE
FUNCTION
D7
D6
D5
D4
D3
D2
D1
D0
0Dh
0000
000x
PWM1
instantaneous duty
cycle
MSB
(128/240)
—
—
—
—
—
LSB
(2/240)
—
R
0Eh
0000
000x
PWM2
instantaneous duty
cycle
MSB
(128/240)
—
—
—
—
—
LSB
(2/240)
—
R/W
0Fh
0000
0000
Channel 1
fan-start
temperature
MSB
—
—
—
—
—
—
LSB
R/W
10h
0000
0000
Channel 2
fan-start
temperature
MSB
—
—
—
—
—
—
LSB
R/W
11h
0000
000x
Fan
configuration
Hysteresis:
0 = 5°C, 1
= 10°C
Fan 1:
control 1
= Ch 1
Fan 1:
control 1
= Ch 2
Fan 2:
control 1
= Ch 1
Fan 2:
control 1
= Ch 2
—
—
R/W
12h
1011
01xx
Duty-cycle
rate of
change
Temp
step: 0 =
1°C,
1 2°C
Fan 1 MSB
—
Fan 1
LSB
Fan 2
MSB
—
Fan 2
LSB
—
—
R/W
13h
0101
0101
Duty-cycle
step size
Fan 1 MSB
—
—
Fan 1
LSB
Fan 2
MSB
—
—
Fan 2
LSB
R/W
14h
010x
xxxx
PWM
frequency
select
Select A
Select B
Select C
—
—
—
—
—
R/W
15h
xx00
000*
GPIO
function
—
—
GPIO5:
0=
output; 1
= input
GPIO4:
0=
output; 1
= input
GPIO3:
0=
output; 1
= input
GPIO2:
0=
output; 1
= input
GPIO1:
0=
output; 1
= input
GPIO0:
0=
output; 1
= input
R/W
16h
xx11
111*
(Note 1)
GPIO value
—
—
GPIO5
GPIO4
GPIO3
GPIO2
GPIO1
GPIO0
R/W
17h
0000
0000
Thermistor
offset
register
Th1 MSB
(sign)
—
—
Th1 LSB
(2°C)
Th2 MSB
(sign)
—
—
Th2 LSB
(2°C)
R
18h
1111
1111
Tach1 value
register
—
—
—
—
—
—
—
—
R
19h
1111
1111
Tach2 value
register
—
—
—
—
—
—
—
—
R/W
1Ah
1111
1111
Tach1 limit
register
—
—
—
—
—
—
—
—
R/W
1Bh
1111
1111
Tach2 limit
register
—
—
—
—
—
—
—
—
R/W ADD
R
______________________________________________________________________________________
13
MAX6615/MAX6616
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
Table 3. Register Map (continued)
R/W ADD
POR
STATE
FUNCTION
D7
D6
D5
D4
1=
disabled
fan 2 tach
Fan status
byte
1 = fan 1
failure
1 = fan 2
failure
1=
disabled
fan 1
tach
D3
D2
1=
1=
measure measure
fan 1
fan 2
when it is when it is
full speed full speed
D1
D0
1 = mask
FAN_FAIL
pin
1 = fan 1
fail sets
fan 2
100%
R/W
1Ch
0000
0000
R
1Eh
0000
0000
Channel 1
temp LSBs
MSB
(1/2°C)
—
LSB
(1/8°C)
—
—
—
—
—
R
1Fh
0000
0000
Channel 2
temp LSBs
MSB
(1/2°C)
—
LSB
(1/8°C)
—
—
—
—
—
R
FDh
0000
0001
Read device
revision
0
0
0
0
0
0
0
1
R
FEh
0110
1000
Read device
ID
0
1
1
0
1
0
0
0
R
FFh
0100
1101
Read
manufacturer
ID
0
1
0
0
1
1
0
1
*GPIO0 POR values are set by PRESET.
Table 4. Configuration Byte Definition (02h)
POR
STATE
BIT
NAME
7
RUN/STANDBY
0
Set to zero for normal operation. Set to 1 to suspend conversions and PWM outputs.
6
POR
0
Set to 1 to perform reset of all device registers.
5
TIMEOUT
0
Set TIMEOUT to zero to enable SMBus timeout for prevention of bus lockup. Set to 1 to
disable this function.
4
FAN1 PWM INVERT
1
Set fan PWM invert to zero to force PWM1 low when the duty cycle is 100%. Set to 1 to
force PWM1 high when the duty cycle is 100%.
3
FAN2 PWM INVERT
1
Set fan PWM invert to zero to force PWM2 low when the duty cycle is 100%. Set to 1 to
force PWM2 high when the duty cycle is 100%.
14
FUNCTION
2
MIN DUTY CYCLE
0
Set min duty cycle to zero for a 0% duty cycle when the measured temperature is below the
fan-temperature threshold in automatic mode. When the temperature equals the fantemperature threshold, the duty cycle is the value in the fan-start duty-cycle register, and it
increases with increasing temperature.
Set min duty cycle to 1 to force the PWM duty cycle to the value in the fan-start duty-cycle
register when the measured temperature is below the fan-temperature threshold. As the
temperature increases above the temperature threshold, the duty cycle increases as
programmed.
1
TEMPERATURE
SOURCE SELECT
0
Selects either local or remote 2 as the source for temperature channel 2 register data.
When D1 = 0, the MAX6615/MAX6616 measure remote 2 and when D1 = 1, the
MAX6615/MAX6616 measure the internal die temperature.
0
SPIN-UP DISABLE
0
Set spin-up disable to 1 to disable spin-up. Set to zero for normal fan spin-up.
______________________________________________________________________________________
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
The POR state of the PWM instantaneous duty-cycle
register is 00h.
Channel 1 and Channel 2 Fan-Start Temperature
(0Fh and 10h)
These registers contain the temperatures at which fan
control begins (in automatic mode). See the Automatic
PWM Duty-Cycle Control section for details on setting
the fan-start thresholds. The POR state of the channel 1
and channel 2 fan-start temperature registers is 00h.
Fan Configuration (11h)
The fan-configuration register controls the hysteresis
level, temperature step size, and whether the remote or
local diode controls the PWM2 signal (see Table 3). Set
bit D7 of the fan-configuration register to zero to set the
hysteresis value to 5°C. Set bit D7 to 1 to set the hysteresis value to 10°C. Set bit D6 to zero to set the fancontrol temperature step size to 1°C. Set bit D6 to 1 to
set the fan-control temperature step size to +2°C. Bits
D5 to D2 select which PWM_ channel 1 or channel 2
controls (see Table 3). If both are selected for a given
PWM_, the highest PWM value is used. If neither is
selected, the fan is controlled by the value written to the
fan-target duty-cycle register. Also in this mode, the value
written to the target duty-cycle register is not limited by
the value in the maximum duty-cycle register. It is, however, clipped to 240 if a value above 240 is written. The
POR state of the fan-configuration register is 00h.
Duty-Cycle Rate of Change (12h)
Bits D7, D6, and D5 (channel 1) and D4, D3, and D2
(channel 2) of the duty-cycle rate-of-change register set
the time between increments of the duty cycle. Each
increment is 2/240 of the duty cycle (see Table 5). This
allows the time from 33% to 100% duty cycle to be
adjusted from 5s to 320s. The rate-of-change control is
always active in manual mode. To make instant changes,
set bits D7, D6, and D5 (channel 1) or D4, D3, and D2
(channel 2) = 000. The POR state of the duty-cycle rateof-change register is B4h (1s between increments).
Table 5. Setting the Time Between DutyCycle Increments
D7:D5, D4:D2
TIME BETWEEN
INCREMENTS (s)
TIME FROM 33%
TO 100% (s)
000
0
0
001
0.0625
5
010
0.125
10
011
0.25
20
100
0.5
40
101
1
80
110
2
160
111
4
320
Table 6. Setting the Duty-Cycle Step Size
D7:D4, D3:D0
CHANGE IN DUTY
CYCLE PER
TEMPERATURE
STEP
0000
0
TEMPERATURE
RANGE FOR FAN
CONTROL
(1°C STEP, 33%
TO 100%)
0
0001
2/240
80
0010
4/240
40
0011
6/240
27
0100
8/240
20
0101
10/240
16
…
…
...
1000
16/240
10
...
...
...
1111
31/240
5
______________________________________________________________________________________
15
MAX6615/MAX6616
zero, the duty cycle is zero below the fan-start temperature and has this value when the fan-start temperature
is reached. A value of 240 represents 100% duty cycle.
Writing any value greater than 240 causes the fan
speed to be set to 100%. The POR state of the fan-start
duty-cycle register is 60h, 40%.
PWMOUT Max Duty Cycle (09h and 0Ah)
The PWM maximum duty-cycle register sets the maximum allowable PWM duty cycle between 2/240 (0.83%
duty cycle) and 240/240 (100% duty cycle). Any values
greater than 240 are recognized as 100% maximum
duty cycle. The POR state of the PWM maximum dutycycle register is F0h, 100%. In manual-control mode,
this register is ignored.
PWM Target Duty Cycle (0Bh and 0Ch)
In automatic fan-control mode, this register contains the
present value of the target PWM duty cycle, as determined by the measured temperature and the dutycycle step size. The actual duty cycle requires time
before it equals the target duty cycle if the duty-cycle
rate-of-change register is set to a value other than zero.
In manual fan-control mode, write the desired value of
the PWM duty cycle directly into this register. The POR
state of the fan-target duty-cycle register is 00h.
PWM1 Instantaneous Duty Cycle,
PWM2 Instantaneous Duty Cycle (0Dh, 0Eh)
These registers always contain the duty cycle of the
PWM signals presented at the PWM output.
MAX6615/MAX6616
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
The MSB is the sign bit and the LSB is 2°C. The POR
state for this register is 00h.
Table 7. PWM Frequency Select
PWM
FREQUENCY (Hz)
SELECT A
20
0
0
0
33
0
1
0
50
1
0
0
100
1
1
0
35k
X
X
1
SELECT B
SELECT C
Note: At 35kHz, duty-cycle resolution is decreased from a resolution of 2/240 to 4/240.
Duty-Cycle Step Size (13h)
Bits D7–D4 (channel 1) and bits D3–D0 (channel 2) of the
duty-cycle step-size register change the size of the dutycycle change for each temperature step. The POR state
of the duty-cycle step-size register is 55h (see Table 6).
PWM Frequency Select (14h)
Set bits D7, D6, and D5 (select A, B, and C) in the PWM
frequency-select register to control the PWM frequency
(see Table 7). The POR state of the PWM frequencyselect register is 40h, 33Hz. The lower frequencies are
usually used when driving the fan’s power-supply pin as
in the Typical Application Circuit, with 33Hz being the
most common choice. The 35kHz frequency setting is
used for controlling fans that have logic-level PWM input
pins for speed control. The minimum duty-cycle resolution
is decreased from 2/240 to 4/240 at the 35kHz frequency setting. For example, a result that would return a value
of 6/240 is truncated to 4/240.
GPIO Function Register (15h) (MAX6616)
The GPIO function register (15h) sets the GPIO states.
Write a zero to set a GPIO as an output. Write a 1 to set
a GPIO as an input.
Tachometer Value Registers (18h and 19h)
The tachometer value registers contain the tachometer
count values for each fan. The MAX6615/MAX6616
measure the tachometer signal every 67s. It counts the
number of clock cycles between two tachometer pulses
and stores the value in the corresponding channel register. The POR state of this register is FFh.
Tachometer Limit Registers (1Ah and 1Bh)
The tachometer limit registers contain the tachometer
limits for each fan. If the value in the tach1 value register (18h) ever exceeds the value stored in 1Ah, a channel 1 fan failure is detected. If the value in the Tach2
value register (19h) ever exceeds the value stored in
1Bh, a channel 2 fan failure is detected. The POR state
of these registers is FFh.
Fan Configuration/Status Register (1Ch)
The fan configuration/status register contains the status
and tachometer control bits for both fans. Bits D7 and
D6 indicate whether a fan has failed the maximum
tachometer limits in registers 1Ah and 1Bh. Setting bits
D5 and D4 disables the tachometer for each fan. The
speed is not measured when these bits are set. Setting
bits D3 and D2 measure the fan speed only during
spin-up or when it reaches 100% duty cycle. Bit D1 is
the FAN_FAIL output mask. Bit D0 is the FAN_FAIL
cross drive enable. Setting this bit enables fan 2 to go
to full speed when fan 1 fails or vice versa.
Extended Temperature Registers
(1Eh and 1Fh)
The extended temperature registers contain the low-byte
results of temperature measurements. The value of the
MSB is 0.5°C and the value of D5 is 0.125°C. The POR
states of these registers are 00h.
GPIO Value Register (16h) (MAX6616)
The GPIO value register (16h) contains the state of
each GPIO input when a GPIO is configured as an
input. When configured as an output, write a 1 or zero
to set the value of the GPIO output.
Thermistor Offset Register (17h)
The thermistor offset register contains the offset for both
of the thermistors in two’s complement. Bits D7, D6, D5,
and D4 set the offset for temperature channel 1. Bits
D3, D2, D1, and D0 set the offset for temperature channel 2. The values in this register allow the thermistor
temperature readings to be shifted to help compensate
for different thermistor characteristics or different values
of REXT and apply to thermistor measurements only.
16
______________________________________________________________________________________
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
MAX6615/MAX6616
MEASUREMENT vs. TEMPERATURE
MAX6615/MAX6616 ERROR
4
120
OPTIMIZED FOR +30°C TO +100°C
2
100
MEASUREMENT (°C)
ERROR (°C)
0
-2
-4
-6
80
60
40
-8
20
-10
-12
0
0
20
40
60
100
80
TEMPERATURE (°C)
120
140
Figure 9. Data Error vs. Temperature Using a Betatherm
10K3A1 Thermistor
Applications Information
Thermistor Considerations
NTC thermistors are resistive temperature sensors
whose resistance decreases with increasing temperature. They are available in a wide variety of packages
that are useful in difficult applications such as measurement of air or liquid temperature. Some can operate
over temperature ranges beyond that of most ICs. The
relationship between temperature and resistance in an
NTC thermistor is very nonlinear and can be described
by the following approximation:
1
= A + B In(R) + C[In(R)]3
T
where T is absolute temperature in Kelvin, R is the thermistor’s resistance, and A, B, and C are coefficients that
vary with manufacturer and material characteristics.
The highly nonlinear relationship between temperature
and resistance in an NTC thermistor makes it somewhat
more difficult to use than a digital-output temperaturesensor IC. However, by connecting the thermistor in
series with a properly chosen resistor and using the
MAX6615/MAX6616 to measure the voltage across the
resistor, a reasonably linear transfer function can be
obtained over a limited temperature range. Accuracy
increases over smaller temperature ranges.
Figures 9 and 10 show a good relationship between
temperature and data. This data was taken using a
popular thermistor model, the Betatherm 10K3A1, with
REXT = 1.6kΩ. Using these values produces data with
-50
0
50
100
150
TEMPERATURE (°C)
Figure 10. Measured Temperature vs. Actual Temperature
good conformance to real temperature over a range of
about +30°C to +100°C. Different combinations of thermistors and REXT result in different curves.
ADC Noise Filtering
The integrating ADC has inherently good noise rejection, especially at low-frequency signals such as
60Hz/120Hz power-supply hum. Lay out the PCB carefully with proper external noise filtering for high-accuracy thermistor measurements in electrically noisy
environments.
Filter high-frequency electromagnetic interference
(EMI) at TH_ and REF with an external 100pF capacitor
connected between the two inputs. This capacitor can
be increased to about 2000pF (max), including cable
capacitance. A capacitance higher than 2000pF introduces errors due to the rise time of the switched current source.
Chip Information
PROCESS: BiCMOS
______________________________________________________________________________________
17
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
MAX6615/MAX6616
Pin Configurations
TOP VIEW
PWM1 1
16 PWM2
TACH1 2
ADD0 3
GPIO2 1
24 GPIO3
15 TACH2
GPIO1 2
23 GPIO4
14 SCL
PWM1 3
22 PWM2
13 SDA
TACH1 4
GND 5
12 VCC
GPIO0 5
TH1 6
11 OT
ADD0 6
19 SCL
REF 7
10 GND
ADD1 7
18 SDA
TH2 8
9
GND 8
17 VCC
TH1 9
16 OT
N.C. 10
15 N.C.
REF 11
14 PRESET
TH2 12
13 FAN_FAIL
ADD1 4
MAX6615
FAN_FAIL
QSOP
21 TACH2
MAX6616
20 GPIO5
QSOP
Typical Application Circuits
VFAN
(5V OR 12V)
VCC
10kΩ
VFAN
3.0V TO 5.5V
VFAN
(5V OR 12V)
4.7kΩ
BETATHERM 10K3A1
VCC
TH1
FAN_FAIL
PWM1
VFAN
THERMISTOR
1.6kΩ
100pF
MAX6615
REF
BETATHERM 10K3A1 1.6kΩ
4.7kΩ
TACH1
PWM2
100pF
TH2
TACH2
THERMISTOR
VCC
SDA
TO SMBus
MASTER
10kΩ
SCL
OT
TO CLOCK THROTTLE OR
SYSTEM SHUTDOWN
GND(5) GND(10) ADD0 ADD1
18
______________________________________________________________________________________
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
VFAN
(5V OR 12V)
VCC
10kΩ
VFAN
3.0V TO 5.5V
VFAN
(5V OR 12V)
4.7kΩ
BETATHERM 10K3A1
VCC
TH1
FAN_FAIL
PWM1
VFAN
THERMISTOR
1.6kΩ
100pF
MAX6616
BETATHERM 10K3A1 1.6kΩ
4.7kΩ
TACH1
REF
PWM2
100pF
TH2
TACH2
THERMISTOR
VCC
SDA
TO SMBus
MASTER
10kΩ
SCL
OT
VCC
VCC
TO CLOCK THROTTLE OR
SYSTEM SHUTDOWN
10kΩ
10kΩ
GPIO3
GPIO0
VCC
VCC
10kΩ
10kΩ
GPIO4
GPIO1
VCC
VCC
10kΩ
10kΩ
GPIO5
GPIO2
PRESET
GND
ADD0 ADD1
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
16 QSOP
E16-1
21-0055
24 QSOP
E24-1
21-0055
______________________________________________________________________________________
19
MAX6615/MAX6616
Typical Application Circuits (continued)
MAX6615/MAX6616
Dual-Channel Temperature Monitors and
Fan-Speed Controllers with Thermistor Inputs
Revision History
REVISION
NUMBER
REVISION
DATE
DESCRIPTION
0
—
1
7/05
Initial release
—
2
10/08
Specified POR values for registers that were inconsistent with Table 3.
PAGES
CHANGED
—
—
10, 15, 16
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.
20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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