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PDF MAX6665ASA55 Data sheet ( Hoja de datos )
| Número de pieza | MAX6665ASA55 | |
| Descripción | Fan Controller/Driver with Factory- Programmed Temperature Thresholds | |
| Fabricantes | Maxim Integrated | |
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19-2056; Rev 0; 5/01
Fan Controller/Driver with Factory-
Programmed Temperature Thresholds
General Description
The MAX6665 is a fully integrated thermal switch with
an internal power transistor for driving a cooling fan
rated up to 24V and 250mA. When the MAX6665’s tem-
perature rises above a factory-programmed threshold,
the FANOUT pin becomes active and powers the fan.
The MAX6665 is available with factory-programmed fan
activation threshold temperatures from +40°C to +70°C
in 5°C increments. Accuracy of the fan activation trip
point is ±1°C (typ) and ±3°C (max). The trip point’s hys-
teresis is pin selectable to 1°C, 4°C, or 8°C. Two open-
drain logic outputs indicate overtemperature con-
ditions: WARN is activated when the temperature is
15°C above the fan activation threshold, and OT is acti-
vated when the temperature is 30°C above the thresh-
old. These features can be used to safely power down
systems that are overheated.
The MAX6665 operates from a +2.7V to +5.5V power
supply, and the associated fan can be powered from
4.5V to 24V. It is available in an 8-pin SO package and
operates from -40°C to +125°C.
Applications
Notebook and Desktop Computers
Servers
PC Power Supplies
Laboratory Instruments
Card Racks
Typical Operating Circuit
+4.5V TO +24V
100mA TO 250mA
COOLING FAN
Features
o On-Chip 250mA Fan Switch
o No External Components Required
o Factory-Programmed Thresholds
o Two Overtemperature Warning Signals
o Pin-Selectable 1°C, 4°C, and 8°C Hysteresis
o Low 65µA Supply Current
PART
MAX6665ASA40
MAX6665ASA45
MAX6665ASA50
MAX6665ASA55
MAX6665ASA60
MAX6665ASA65
MAX6665ASA70
*Exposed paddle
Ordering Information
TEMP.
RANGE
-40°C to
+125°C
-40°C to
+125°C
-40°C to
+125°C
-40°C to
+125°C
-40°C to
+125°C
-40°C to
+125°C
-40°C to
+125°C
PIN-
THRESHOLD
PACKAGE
8 SO-EP*
40°C
8 SO-EP*
45°C
8 SO-EP*
50°C
8 SO-EP*
55°C
8 SO-EP*
60°C
8 SO-EP*
65°C
8 SO-EP*
70°C
Pin Configuration
+3.3V
1µF
VDD FANOUT
MAX6665
HYST
WARN
FORCEON
OT
GND FANON
VDD
100kΩ
VDD
100kΩ
TOP VIEW
GND 1
FORCEON 2
HYST 3
FANON 4
MAX6665
8 FANOUT
7 VDD
6 WARN
5 OT
SO
________________________________________________________________ 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  
Fan Controller/Driver with Factory-
Programmed Temperature Thresholds
+4.5V TO +24V
100mA TO 250mA
COOLING FAN
+3.3V
1µF
VDD FANOUT
MAX6665
HYST
WARN
VDD
100kΩ
I/O µP
FORCEON
FANON
OT
GND
VDD
100kΩ
SYSTEM POWER
SHUTDOWN
I/O
Figure 1. High-Reliability, Fail-Safe Fan Controller and Temperature Monitor
increases by a maximum of:
51°C/W x 0.03125W = 1.59°C
Therefore, the effective hysteresis is about 1.59°C high-
er than the hysteresis selected by the HYST pin. For
example, setting the HYST pin for 8°C of hysteresis
results in an effective hysteresis of about 9.6°C.
A larger fan with a power-supply current of 250mA
causes a maximum voltage drop of 0.6V at the output
pin. This results in 150mW power dissipation and the
die temperature increases by:
51°C/W x 0.150W = 7.65°C
If the HYST pin has been set for 8°C of hysteresis, the
total effective hysteresis will be about 15.7°C.
Using fans with somewhat higher operating current
than 250mA results in higher voltage across the output
transistor. The increased power dissipation caused by
the higher current and voltage levels will increase self-
heating, thereby increasing the effective hysteresis.
When using higher-power fans, be sure that the
MAX6665’s power dissipation does not cause so much
self-heating that the MAX6665 stays on constantly.
Locating the MAX6665
The location of the MAX6665 in the system affects its
operation. Because the fan is turned on and off based
on the MAX6665’s die temperature, place the MAX6665
close to major heat-generating components in the sys-
tem—a high-speed CPU or a power device, for exam-
ple. A higher supply voltage reduces the FANOUT
voltage, which reduces the self-heating effects.
The die temperature of the MAX6665 tracks the tempera-
ture of its leads and the EP. If it is soldered to a PC board,
it quickly reaches the temperature of the traces in that
section of the circuit board. Air temperature affects the die
temperature. Since the plastic package does not conduct
heat as well as the leads, the effect of air temperature is
much less than that of lead temperature.
Layout Issues
The MAX6665’s GND pin is ground return for the fan dri-
ver and the device. Large fan current induces noise
(ground bounce) to the MAX6665. Bypass VDD to GND
with a 1µF tantalum capacitor located as close to the
MAX6665 as possible. For long VDD and GND lines, an
additional bypass capacitor may be needed. The bypass
capacitor reduces GND noise. The EP is internally con-
nected to the GND pin. Solder the EP to the ground plane
for better electrical and thermal performance.
_______________________________________________________________________________________ 5
5 Page | ||
| Páginas | Total 6 Páginas | |
| PDF Descargar | [ Datasheet MAX6665ASA55.PDF ] | |
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