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PDF MAX6687AU40H Data sheet ( Hoja de datos )
| Número de pieza | MAX6687AU40H | |
| Descripción | Local/Remote Temperature Switches in a MAX Package | |
| Fabricantes | Maxim Integrated | |
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19-2636; Rev 2; 11/03
Local/Remote Temperature Switches in a
µMAX Package
General Description
The MAX6687/MAX6688 comprise a remote-junction
temperature switch and a local temperature switch in a
single package. The remote-junction switch uses an
external P-N junction (typically a diode-connected tran-
sistor on the die of an external CPU, ASIC, or FPGA) as
a sensing element to measure the remote temperature.
The remote-junction temperature switch has a factory-
programmed trip temperature threshold of either
+120°C or +125°C. The local temperature switch has a
pin-programmable temperature threshold that is set by
connecting pins S1 and S2 to ground, to VDD, or leav-
ing them floating. Hysteresis for both local and remote
thresholds is 5°C. The MAX6687/MAX6688 do not
assert on transient (single-sample) faults or when
power is first applied.
The MAX6687 has two open-drain active-low outputs
while the MAX6688 has two push-pull active-high out-
puts. TREMOTE asserts a logic signal when the remote
temperature exceeds the factory-programmed +120°C
or +125°C trip threshold. TLOCAL is asserted when the
die temperature exceeds the pin-programmed thresh-
old, which is controlled by pins S1 and S2. The local
thresholds are available in two ranges in 5°C incre-
ments. The two ranges are +40°C to +80°C and +75°C
to +115°C.
The MAX6687/MAX6688 operate from a 3.0V to 5.5V
power supply and are available in a space-saving 8-pin
µMAX package.
Applications
CPU Temperature Protection
FPGA Temperature Protection
Fan Control
Temperature Alarms
3.3V
DXP VDD
3.3V
MAX6687
CS
DXN TREMOTE
µP S1
TLOCAL
S2
GND
TO SYSTEM
SHUTDOWN
Features
o Pin-Programmable Local Temperature Threshold
in 5°C Increments in Two Distinct Ranges: +40°C
to +80°C and +75°C to +115°C
o Factory-Programmed Remote Threshold:
+120°C (L Suffix) or +125°C (H Suffix)
o Open-Drain Active-Low Outputs (MAX6687)
o CMOS Push-Pull, Active-High Outputs (MAX6688)
o ±1.5°C Accuracy
o 2Hz Temperature Sampling Rate
o 215µA Average Supply Current
o 3.0V to 5.5V Power-Supply Voltage
o 8-Pin µMAX Package
PART
MAX6687AU40L
MAX6687AU40H
MAX6687AU75L
MAX6687AU75H
MAX6688AU40L
MAX6688AU40H
MAX6688AU75L
MAX6688AU75H
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
-40°C to +125°C
PIN-PACKAGE
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
Pin Configurations/Functional Diagrams/Selector Guide
appear at end of data sheet.
Typical Operating Circuit
3.3V
TO SYSTEM
SHUTDOWN
DXP VDD
TREMOTE
CS MAX6688
DXN
12V
µP S1
S2
TLOCAL
GND
N
________________________________________________________________ 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  
Local/Remote Temperature Switches in a
µMAX Package
Table 1. Local Temperature Trip Threshold Selection
S1 S2
GND
GND
GND
FLOAT
FLOAT
FLOAT
VDD
VDD
VDD
GND
FLOAT
VDD
GND
FLOAT
VDD
GND
FLOAT
VDD
MAX6687AUA40L/MAX6687AUA40H/
MAX6688AUA40L/MAX6688AUA40H
LOCALTEMPERATURE TRIP THRESHOLD (°C)
+40
+45
+50
+55
+60
+65
+70
+75
+80
MAX6687AUA75L/MAX6687AUA75H/
MAX6688AUA75L/MAX6688AUA75H
LOCAL TEMPERATURE TRIP THRESHOLD (°C)
+75
+80
+85
+90
+95
+100
+105
+110
+115
Applications Information
Remote-Diode selection
The MAX6687/MAX6688 are optimized to measure the
die temperature of CPUs and other ICs that have on-
chip temperature-sensing diodes. These on-chip
diodes are substrate PNPs with their collectors ground-
ed. Connect the base of the PNP to DXN and the emit-
ter to DXP. When using a discrete, diode-connected
NPN or PNP as a sensing diode, use a good-quality
small-signal device. Examples are listed in Table 2.
Tight specifications for forward current gain indicate
the manufacturer has good process controls and that
the devices have consistent VBE characteristics.
Always use a transistor for the sensing junction; diodes
do not work.
The MAX6687/MAX6688 are optimized for use with
thermal-sensing transistors with an ideality factor of
1.008. Different ideality factors cause predictable, usu-
ally small deviations in trip temperature thresholds.
Table 2. Sensor Transistor Manufacturers
MANUFACTURER
Central Semiconductor (USA)
Rohm Semiconductor (Japan)
Samsung (Korea)
Siemens (Germany)
MODEL NO.
CMPT3904
SST3904
KST3904-TF
SMBT3904
Noise-Filtering Capacitors
A quality ceramic capacitor must be connected across
the DXP/DXN inputs to maintain temperature threshold
accuracy by filtering out noise. The capacitor should be
located physically close to the DXP/DXN pins and
should typically have a value of 2200pF. Larger capaci-
tor values can cause temperature measurement errors.
A 50% increase from the recommended capacitor
value can cause up to ±1°C error.
Sensing Circuit Board and
Ambient Temperature
Temperature switches like the MAX6687/MAX6688 that
sense their own die (local) temperatures must be
mounted on or close to the object whose temperature
they are intended to measure. The MAX6687/MAX6688
can accurately measure the temperature of a circuit
board to which they are soldered because the package
leads provide a good thermal path between the circuit
board and their own die. If the MAX6687/MAX6688 are
intended to be triggered by the temperature of a heat-
generating component on the circuit board, they should
be mounted as close as possible to that component
and should share supply and ground traces (if they are
not noisy) with that component where possible. The
thermal path between the plastic package and the die
is not as good as the path through the package leads,
so the MAX6687/MAX6688 are less sensitive to the sur-
rounding air temperature than they are to the tempera-
ture of their package leads, but they can be
successfully used to respond to the ambient tempera-
ture if the circuit board is designed to track the ambient
temperature.
Chip Information
TRANSISTOR COUNT: 7765
PROCESS: BiCMOS
_______________________________________________________________________________________ 5
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