19-2133; Rev 1; 9/02
Remote Temperature Switches with Integrated
Fan Controller/Driver
General Description
Features
The MAX6668/MAX6670 remote-junction thermal
switches with an internal power transistor drive a cool-
ing fan rated for supply voltages up to +12V and
250mA. These devices measure the temperature of an
external P-N junction (typically a diode-connected tran-
sistor) and turn on the fan power switch when the
remote temperature rises above a factory-programmed
threshold. Self-contained and requiring no software
development, the MAX6668/MAX6670 are simple
“drop-in” fan-control solutions for a variety of systems.
ꢀ +12V, 250mA Integrated Fan Driver
ꢀ No Calibration Required
ꢀ Pin-Selectable 4°C, 8°C, or 12°C Hysteresis
(MAX6670)
ꢀ Factory-Programmed Temperature Thresholds
from +40°C to +75°C
ꢀ Overtemperature Warning Signals
ꢀ 110µA (typ) Supply Current
The MAX6670 features an open-drain WARN output
that goes active when the remote temperature exceeds
the factory-programmed fan activation threshold by
+15°C. The MAX6670 features an open-drain OT output
that goes active when the remote temperature exceeds
the factory-programmed threshold by +30°C. The
MAX6668/MAX6670 provide a fan-control input,
FORCEON, that allows the fan to be driven externally,
regardless of temperature.
ꢀ Space-Saving 8-Pin and 10-Pin µMAX Packages
Ordering Information
PART*
TEMP. RANGE
-40 C to +125 C
-40 C to +125 C
PIN-PACKAGE
8 µMAX
MAX6668AUA_ _
MAX6670AUB_ _
10 µMAX
Available temperature thresholds range from +40°C to
+75°C in 5°C increments. Hysteresis is preset to 8°C on
the MAX6668 or pin selectable to 4°C, 8°C, or 12°C
using a three-level logic input on the MAX6670.
Temperature threshold accuracy is 1°C (typ) and
2.2°C (max) for remote-junction temperatures from
+40°C to +75°C.
*These parts are offered in eight standard temperature ver-
sions from +40°C through +75°C in 5°C increments. To com-
plete the suffix information, select an available temperature trip
point in degrees centigrade and fill in the blank. For example,
the MAX6670AUB065 describes a MAX6670 in a 10-pin µMAX
package with +65°C trip point.
The MAX6668/MAX6670 operate from a +3V to +3.6V
power supply, and are specified over the automotive
temperature range (-40°C to +125°C). The MAX6668 is
offered in an 8-pin µMAX package and the MAX6670 is
available in a space-saving 10-pin µMAX package.
Typical Applications Circuit
+12V
Applications
Notebook and Desktop Computers
250mA
+3.3V
FAN
Network Switches
V
DD
DXP
DXN
FANOUT
V
PC Power Supplies
Laboratory Instruments
Card Racks
DD
C
S
10k
2200pF
MAX6670
2N3904
WARN
V
10k
DD
Temperature Alarms
Fan Controls
OT
HYST
V
DD
FORCEON
GND
PGND
Pin Configuration appears at end of data sheet.
Typical Operating Circuit appears at end of data sheet.
________________________________________________________________ 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.