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PDF MAX6651 Data sheet ( Hoja de datos )
| Número de pieza | MAX6651 | |
| Descripción | Fan-Speed Regulators and Monitors | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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EVALUATION KIT AVAILABLE
MAX6650/MAX6651
Fan-Speed Regulators and Monitors
with SMBus/I2C-Compatible Interface
General Description
The MAX6650/MAX6651 fan controllers use an
SMBus/I2C-compatible interface to regulate and moni-
tor the speed of 5VDC/12VDC brushless fans with built-
in tachometers. They automatically force the fan’s
tachometer frequency (fan speed) to match a prepro-
grammed value in the Fan-Speed Register by using an
external MOSFET or bipolar transistor to linearly regu-
late the voltage across the fan. The MAX6650 regulates
the speed of a single fan by monitoring its tachometer
output. The MAX6651 also regulates the speed of a sin-
gle fan, but it contains additional tachometer inputs to
monitor up to four fans and control them as a single unit
when they are used in parallel.
The MAX6650/MAX6651 provide general-purpose
input/output (GPIO) pins that serve as digital inputs,
digital outputs, or various hardware interfaces. Capable
of sinking 10mA, these open-drain inputs/outputs can
drive an LED. To add additional hardware control, con-
figure GPIO1 to fully turn on the fan in case of software
failure. To generate an interrupt when a fault condition
is detected, configure GPIO0 to behave as an active-
low alert output. Synchronize multiple devices by set-
ting GPIO2 (MAX6651 only) as an internal clock output
or an external clock input.
The MAX6650 is available in a space-saving 10-pin
µMAX® package, and the MAX6651 is available in a
small 16-pin QSOP package.
________________________Applications
RAID
Servers
Workstations
Desktop Computers
Networking
Telecommunications
____________________________Features
♦ Closed/Open-Loop Fan-Speed Control for
5V/12V Fans
♦ 2-Wire SMBus/I2C-Compatible Interface
♦ Monitors Tachometer Output
Single Tachometer (MAX6650)
Up to Four Tachometers (MAX6651)
♦ Programmable Alert Output
♦ GPIOs
♦ Hardware Full-On Override
♦ Synchronize Multiple Fans
♦ Four Selectable Slave Addresses
♦ 3V to 5.5V Supply Voltage
♦ Small Packages
10-Pin µMAX (MAX6650)
16-Pin QSOP (MAX6651)
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX6650EUB
-40°C to +85°C
10 µMAX
MAX6650EUB+
-40°C to +85°C
10 µMAX
MAX6651EEE
-40°C to +85°C
16 QSOP
MAX6651EEE+
-40°C to +85°C
16 QSOP
+Denotes a lead(Pb)-free/RoHS-compliant package.
Pin Configurations appear at end of data sheet.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Typical Operating Circuit
VCC
3V TO 5.5V
VCC
MAX6650
VFAN
5V OR 12V
10kΩ
SMBus/I2C
INTERFACE
SCL TACH0
SDA FB
FAN
LED
ALERT
GPIO0
FULL ON
GPIO1
OUT
ADD
GND
CCOMP
10μF
For pricing, delivery, and ordering information, please contact Maxim Direct at
1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
19-1784; Rev 5; 12/12
1 page  
MAX6650/MAX6651
Fan-Speed Regulators and Monitors
with SMBus/I2C-Compatible Interface
PIN PIN
MAX6650 MAX6651
11
— 2, 3, 16
24
35
46
58
— 7, 12
69
7 10
— 11
8 13
9 14
10 15
NAME
TACH0
TACH2, TACH3,
TACH1
GND
SDA
SCL
ADD
GPIO4, GPIO3
GPIO1
GPIO0
GPIO2
OUT
VCC
FB
Pin Description
FUNCTION
Tachometer Input. Used to close the loop around the tachometer.
Tachometer Inputs. Used to monitor tachometers only.
Ground
2-Wire Serial-Data Input/Output (open drain)
2-Wire Serial Clock Input
Slave Address Select Input (Table 1)
General-Purpose Input/Output (open drain)
General-Purpose Input/Output (open drain). Configurable to act either as an out-
put or as an input (FULL ON or general purpose).
General-Purpose Input/Output (open drain). Configurable to act as a general
input/output line or an active-low ALERT output.
General-Purpose Input/Output (open drain). Configurable to act as a general
input/output line, an internal clock output, or an external clock input.
Output. Drives the external MOSFET or bipolar transistor.
+3.0V to +5.5V Power Supply
Feedback Input. Closes the loop around the external MOSFET or bipolar tran-
sistor.
Detailed Description
The MAX6650/MAX6651 use an SMBus/I2C-Compatible
interface to regulate and monitor the speed of
5VDC/12VDC brush-less fans with built-in open-collec-
tor/drain tachometers. Regulating fan speed propor-
tionally with temperature saves power, increases fan
life, and reduces acoustic noise. Since fan speed is
proportional to the voltage across the fan, the
MAX6650/MAX6651 control the speed by regulating the
voltage on the low side of the fan with an external MOS-
FET or bipolar transistor.
The MAX6650/MAX6651 each contain two internal con-
trol loops. The first loop controls the voltage across the
fan. The internal digital-to-analog converter (DAC) sets
the reference voltage for an internal amplifier (Figure 1),
which then drives the gate of an external N-channel
MOSFET (or the base of a bipolar transistor) to regulate
the voltage on the low side of the fan. As the reference
voltage provided by the DAC changes, the feedback
amplifier automatically adjusts the feedback voltage,
which changes the voltage across the fan.
The second control loop consists of the internal digital
logic that controls the fan’s speed. The MAX6650/
MAX6651 control fan speed by forcing the tachometer
frequency to equal a reference frequency set by the
Fan-Speed Register, the prescaler, and the internal
oscillator (see the Fan-Speed Register section). When
the tachometer frequency is too high, the value of the
DAC’s input register is increased by the regulator.
Once the DAC voltage increases, the analog control
loop forces the feedback voltage to rise, which reduces
the voltage across the fan. Since fan speed is propor-
tional to the voltage across the fan, the fan slows down.
2-Wire SMBus/I2C-Compatible
Digital Interface
From a software perspective, the MAX6650/MAX6651
appear as a set of byte-wide registers that contain
speed control, tachometer count, alarm conditions, or
configuration bits. These devices use a standard
SMBus/I2C-compatible 2-wire serial interface to access
the internal registers.
Maxim Integrated
5
5 Page 
MAX6650/MAX6651
Fan-Speed Regulators and Monitors
with SMBus/I2C-Compatible Interface
Table 5. GPIO Definition Register
BIT
POR
(DEFAULT)
STATE
MAX6650
PIN
MAX6651
PIN
71
N/A GPIO4
(must be 1)
6
1
N/A
(must be 1)
GPIO3
5:4
11
N/A
(must be 11)
GPIO2
3:2 11
GPIO1
GPIO1
1:0 11
GPIO0
GPIO0
STATE
FUNCTION
0 GPIO4 outputs a logic-low level.
1 GPIO4 outputs a logic-high level or serves as an input.
0 GPIO3 outputs a logic-low level.
1 GPIO3 outputs a logic-high level or serves as an input.
00 GPIO2 serves as an external clock input.
01 GPIO2 serves as an internal clock output.
10 GPIO2 outputs a logic-low level.
11 GPIO2 outputs a logic-high level or serves as an input.
00 GPIO1 outputs a logic-high level or serves as an input.
01 GPIO1 serves as a FULL ON input.
10 GPIO1 outputs a logic-low level.
11 GPIO1 outputs a logic-high level or serves as an input.
00 GPIO0 outputs a logic-high level or serves as an input.
01 GPIO0 serves as an ALERT output.
10 GPIO0 outputs a logic-low level.
11 GPIO0 outputs a logic-high level or serves as an input.
Table 6. GPIO Status Register
BIT
7 (MSB) to 5
4
3
2
1
0 (LSB)
NAME
Always 0
GPIO4 (MAX6651 only)
GPIO3 (MAX6651 only)
GPIO2 (MAX6651 only)
GPIO1
GPIO0
POR
(DEFAULT
STATE)
0
1
1
1
1
1
Alarm Status Register if the condition that caused the
alarm is removed.
Tachometer
The Tachometer Count Registers record the number of
pulses on the corresponding tachometer input during the
period defined by the Tachometer Count-Time Register.
The MAX6651 contains three additional tachometer
inputs, which may be used to monitor additional fans. For
accurate control of multiple fans, use identical fans.
The Tachometer Count-Time Register sets the integration
time over which the MAX6650/MAX6651 count tachome-
ter pulses. The devices can count up to 255 (FFh) pulses
during the selected count time. If more than 255 pulses
occur, the IC sets the overflow alarm and the Tachometer
Count Register reports the maximum value of 255. Set
the time register so the count register will not overflow
under worst-case conditions (maximum fan speed) while
maximizing resolution. Calculate the maximum measur-
able fan speed and minimum resolution with the following
equations:
Max Fan Speed (in RPS) = 255 / (2 x tCOUNT)
Min Resolution (in RPS) = 1 / (2 x tCOUNT)
where tCOUNT is the tachometer count time; 1kHz is the
maximum allowable tachometer input frequency for the
MAX6650/MAX6651.
Maxim Integrated
11
11 Page | ||
| Páginas | Total 25 Páginas | |
| PDF Descargar | [ Datasheet MAX6651.PDF ] | |
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