MAX6661 Datasheet, PDF (1/19 Pages) Maxim Integrated Products – Remote Temperature-Controlled Fan-Speed Regulator with SPI-Compatible Interface

19-2337; Rev 0; 1/02
Remote Temperature-Controlled Fan-Speed
Regulator with SPI-Compatible Interface
General Description
The MAX6661 is a remote temperature sensor and fan-
speed regulator that provides complete closed-loop fan
control. The remote temperature sensor is typically a
common-collector PNP, such as a substrate PNP of a
microprocessor, or a diode-connected transistor, typi-
cally a low-cost, easily mounted 2N3904 NPN type or
2N3906 PNP type.
The device also incorporates a closed-loop fan con-
troller that regulates fan speed with tachometer feed-
back. The MAX6661 compares temperature data to a
fan threshold temperature and gain setting, both pro-
grammed over the SPI™ bus by the user. The result is
automatic fan control that is proportional to the remote-
junction temperature. The temperature feedback loop
can be broken at any time for system control over the
speed of the fan.
Fan speed is voltage controlled as opposed to PWM
controlled, greatly reducing acoustic noise and maxi-
mizing fan reliability. An on-chip power device drives
fans rated up to 250mA.
Temperature data is updated every 500ms and is read-
able at any time over the SPI interface. The MAX6661 is
accurate to 1°C (max) when the remote junction is
between +60°C to +100°C. Data is formatted as a 10-
bit + sign word with 0.125°C resolution.
The MAX6661 is specified between -40°C to +125°C
and is available in a 16-pin QSOP package.
Applications
Telecom Systems
Servers
Workstations
Electronic Instruments
Pin Configuration appears at end of data sheet.
SPI is a trademark of Motorola, Inc.
Features
o Integrated Thermal Measurement and Fan
Regulation
o Programmable Fan Threshold Temperature
o Programmable Temperature Range for Full-Scale
Fan Speed
o Accurate Closed-Loop Fan-Speed Regulation
o On-Chip Power Device Drives Fans Rated
Up to 250mA
o Programmable Under/Overtemperature Alarms
o SPI-Compatible Serial Interface
o ±1°C (+60°C to +100°C) Thermal-Sensing
Accuracy
PART
MAX6661AEE
Ordering Information
TEMP RANGE PIN-PACKAGE
-40°C to +125°C 16 QSOP
Typical Operating Circuit
12V
0.1µF
3V TO 5.5V
50Ω
V_FAN
V_CC
5kΩ
ALERT
1µF
FAN
TACH IN
OVERT
PENTIUM
FAN MAX6661
DXP
SC
2200pF
SDIN
DXN
AGND
DOUT
CS
PGND
10kΩ
EACH
INTERRUPT
TO µP
TO SYSTEM
SHUTDOWN
SPI CLOCK
SPI DATA IN
SPI DATA OUT
SPI CHIP SELECT
________________________________________________________________ Maxim Integrated Products 1
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