MAX6650 Datasheet, PDF (1/25 Pages) Maxim Integrated Products – Fan-Speed Regulators and Monitors with SMBus/I2C-Compatible Interface

19-1784; Rev 2; 12/01
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 mon-
itor the speed of 5VDC/12VDC brushless fans with built-in
tachometers. They automatically force the fan’s tachome-
ter frequency (fan speed) to match a preprogrammed
value in the Fan-Speed Register by using an external
MOSFET or bipolar transistor to linearly regulate the volt-
age 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 single 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
Desktop Computers
Networking
Workstations Telecommunications
____________________________Features
o Closed/Open-Loop Fan-Speed Control for
5V/12V Fans
o 2-Wire SMBus/I²C-Compatible Interface
o Monitors Tachometer Output
Single Tachometer (MAX6650)
Up to Four Tachometers (MAX6651)
o Programmable Alert Output
o GPIOs
o Hardware Full-On Override
o Synchronize Multiple Fans
o Four Selectable Slave Addresses
o 3V to 5.5V Supply Voltage
o Small Packages
10-Pin µMAX (MAX6650)
16-Pin QSOP (MAX6651)
PART
MAX6650EUB
MAX6651EEE
Ordering Information
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
10 µMAX
16 QSOP
SMBus is a trademark of Intel Corp.
I²C is a trademark of Philips Corp.
Pin Configurations appear at end of data sheet.
Typical Operating Circuit
V_CC
3V TO 5.5V
SMBus/I²C
INTERFACE
V_CC
MAX6650
SCL
TACH0
SDA
FB
V_FAN
5V OR 12V
10kΩ
FAN
LED
ALERT _GPIO0
OUT
FULL ON
GPIO1
ADD
GND
C_COMP
10µF
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