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PDF MAX6641 Data sheet ( Hoja de datos )
| Número de pieza | MAX6641 | |
| Descripción | SMBus-Compatible Temperature Monitor | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX6641 (archivo pdf) en la parte inferior de esta página. Total 17 Páginas | ||
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19-3304; Rev 0; 5/04
SMBus-Compatible Temperature Monitor withwww.DataSheet4U.com
Automatic PWM Fan-Speed Controller
General Description
The MAX6641 temperature sensor and fan controller
accurately measures the temperature of its own die and
the temperature of a remote pn junction. The device
reports temperature values in digital form using a 2-wire
serial interface. The remote pn junction is typically the
emitter-base junction of a common-collector pnp on a
CPU, FPGA, or ASIC.
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 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 device also features an over-temperature alarm
output to generate interrupts, throttle signals, or shut
down signals. The MAX6641 operates from supply volt-
ages in the 3.0V to 5.5V range and typically consumes
500µA of supply current.
The MAX6641 is available in a slim 10-pin µMAX® pack-
age and is available over the automotive temperature
range (-40°C to +125°C).
Desktop Computers
Notebook Computers
Workstations
Servers
Networking Equipment
Industrial
Applications
Features
♦ Tiny 3mm x 5mm µMAX Package
♦ Thermal Diode Input
♦ Local Temperature Sensor
♦ Open-Drain PWM Output for Fan Drive
♦ Programmable Fan Control Characteristics
♦ Automatic Fan Spin-Up Ensures Fan Start
♦ ±1°C Remote Temperature Accuracy (+60°C to
+145°C)
♦ Controlled Rate of Change Ensures Unobtrusive
Fan-Speed Adjustments
♦ Temperature Monitoring Begins at Power-On for
Fail-Safe System Protection
♦ OT Output for Throttling or Shutdown
Ordering Information
PART
MAX6641AUB90
MAX6641AUB92
MAX6641AUB94
MAX6641AUB96
TEMP RANGE
-40°C to
+125°C
-40°C to
+125°C
-40°C to
+125°C
PIN-
PACKAGE
10 µMAX
10 µMAX
10 µMAX
-40°C to
+125°C
10 µMAX
SMBus
ADDRESS
1001 000x
1001 001x
1001 010x
1001 011x
Pin Configuration
Typical Application Circuit appears at end of data sheet.
TOP VIEW
I.C. 1
DXN 2
DXP 3
GND 4
OT 5
MAX6641
10 PWMOUT
9 VCC
8 SMBDATA
7 SMBCLK
6 I.C.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
SMBus is a trademark of Intel Corp.
µMAX
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
SMBus-Compatible Temperature Monitor withwww.DataSheet4U.com
Automatic PWM Fan-Speed Controller
Pin Description
PIN NAME
FUNCTION
1, 6 I.C. Internally Connected. Must be connected to GND.
2
DXN
Combined Remote-Diode Cathode Connection and A/D Negative Input. Connect the cathode of the
remote-diode-connected transistor to DXN.
Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode Channel. Connect
3
DXP
DXP to the anode of a remote-diode-connected temperature-sensing transistor. DO NOT LEAVE
DXP FLOATING; connect to DXN if no remote diode is used. Place a 2200pF capacitor between DXP
and DXN for noise filtering.
4
GND
Ground
Active-Low, Open-Drain, Over-Temperature Output. Use OT as an interrupt, a system shutdown
5 OT signal, or to control clock throttling. OT can be pulled up to 5.5V, regardless of the voltage on VCC.
OT is high impedance when VCC = 0.
7
SMBCLK
SMBus Serial Clock Input. SMBCLK can be pulled up to 5.5V, regardless of VCC. Open drain.
SMBCLK is high impedance when VCC = 0.
8 SMBDATA SMBus Serial Data Input/Output. SMBDATA can be pulled up to 5.5V, regardless of VCC. Open drain.
SMBDATA is high impedance when VCC = 0.
9 VCC Positive Supply. Bypass with a 0.1µF capacitor to GND.
PWM Output to Fan Power Transistor. Connect PWMOUT to the gate of a MOSFET or the base of a
bipolar transistor to drive the fan’s power supply with a PWM waveform. Alternatively, the PWM output
10 PWMOUT can be connected to the PWM input of a fan with direct speed-control capability, or it can be
converted to a DC voltage for driving the fan’s power supply. PWMOUT requires a pullup resistor. The
pullup resistor can be connected to a voltage supply up to 5.5V, regardless of VCC.
Detailed Description
The MAX6641 temperature sensor and fan controller
accurately measures the temperature of its own die and
the temperature of a remote pn junction. The device
reports temperature values in digital form using a 2-
wire serial interface. The remote pn junction is typically
the emitter-base junction of a common-collector pnp on
a CPU, FPGA, or ASIC. The MAX6641 operates from
supply voltages of 3.0V to 5.5V and consumes 500µA
of supply current. The temperature data controls a
PWM output signal to adjust the speed of a cooling fan.
The device also features an over-temperature alarm
output to generate interrupts, throttle signals, or shut
down signals.
SMBus Digital Interface
From a software perspective, the MAX6641 appears as
a set of byte-wide registers that contain temperature
data, alarm threshold values, and control bits. A stan-
dard SMBus-compatible 2-wire serial interface is used
to read temperature data and write control bits and
alarm threshold data. These devices respond to the
same SMBus slave address for access to all functions.
The MAX6641 employs 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 instruc-
tion. Use caution when using the shorter protocols in
multimaster systems, as a second master could over-
write the command byte without informing the first mas-
ter. The MAX6641 has four different slave addresses
available; therefore, a maximum of four MAX6641
devices can share the same bus.
Temperature data within the 0°C to +255°C range can
be read from the read external temperature register
(00h). Temperature data within the 0°C to +125°C range
can be read from the read internal temperature register
(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 are clipped to 00h.
Table 1 details the register address and function,
whether they can be read or written to, and the power-on
reset (POR) state. See Tables 1–5 for all other register
functions and the Register Descriptions section. Figure 4
is the MAX6641 block diagram.
_______________________________________________________________________________________ 5
5 Page 
SMBus-Compatible Temperature Monitor withwww.DataSheet4U.com
Automatic PWM Fan-Speed Controller
Fan Instantaneous Duty Cycle (0Ah)
Read the fan instantaneous duty-cycle register to deter-
mine the duty cycle at PWMOUT at any time. The POR
state of the fan instantaneous duty-cycle register is 00h.
Remote- and Local-Diode
Fan-Start Temperature (0Bh, 0Ch)
These registers contain the temperature threshold val-
ues 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 remote- and local-diode fan-start tempera-
ture registers is 00h.
Fan Configuration (0Dh)
The fan-configuration register controls the hysteresis
level, temperature step size, and whether the remote or
local diode controls the PWMOUT signal; see Table 1.
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
fan-control temperature step size to 1°C. Set bit D6 to 1
to set the fan-control temperature step size to 2°C. Set
bit D5 to 1 to control the fan with the remote-diode’s
temperature reading. Set bit D4 to 1 to control the fan
with the local-diode’s temperature reading. If both bits
D5 and D4 are high, the device uses the highest PWM
value. If both bits D5 and D4 are zero, the MAX6641
runs in manual fan-control mode where only the value
written to the fan-target duty-cycle register (09h) con-
trols the PWMOUT duty cycle. In manual fan-control
mode, the value written to the fan-target duty-cycle reg-
ister 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-configu-
ration register is 00h.
Duty-Cycle Rate of Change (0Eh)
Bits D7, D6, and D5 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 3. 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, D5 = 000. The
POR state of the duty-cycle rate-of-change register is
A0h (1s time between increments).
Duty-Cycle Step Size (0Fh)
Bits D7–D4 of the duty-cycle step-size register change
the size of the duty-cycle change for each temperature
step. The POR state of the duty-cycle step-size register
is 50h; see Table 4.
Table 3. Duty-Cycle Rate-of-Change
Register (0Eh)
D7, D6, D5
000
001
010
011
100
101
110
111
TIME BETWEEN
INCREMENTS (s)
0
0.0625
0.1250
0.2500
0.5000
1.0000
2.0000
4.0000
TIME FROM 33%
TO 100% (s)
0
5
10
20
40
80
160
320
Table 4. Duty-Cycle Step-Size
Register (0Fh)
CHANGE IN DUTY TEMPERATURE RANGE
D7–D4
CYCLE PER
FOR FAN CONTROL
TEMPERATURE STEP (1°C STEP, 33% TO 100%)
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
0/240
2/240
4/240
6/240
8/240
10/240
12/240
14/240
16/240
18/240
20/240
22/240
24/240
26/240
28/240
30/240
N/A
80.00
40.00
26.67
20.00
16.00
13.33
11.43
10.00
8.89
8.00
7.27
6.67
6.15
5.71
5.33
PWM Frequency Select (10h)
Set bits D7, D6, and D5 (select A, select B, and select
C) in the PWM frequency-select register to control the
PWMOUT frequency; see Table 5. The POR state of the
PWM frequency select 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
______________________________________________________________________________________ 11
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| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet MAX6641.PDF ] | |
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