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 V
DD
, 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. T
REMOTE
asserts a logic signal when the remote
temperature exceeds the factory-programmed +120°C
or +125°C trip threshold. T
LOCAL
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.
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
MAX6687/MAX6688
Ordering Information
PART
MAX6687AU40L
MAX6687AU40H
MAX6687AU75L
MAX6687AU75H
MAX6688AU40L
MAX6688AU40H
MAX6688AU75L
MAX6688AU75H
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
Applications
CPU Temperature Protection
FPGA Temperature Protection
Fan Control
Temperature Alarms
Pin Configurations/Functional Diagrams/Selector Guide
appear at end of data sheet.
Typical Operating Circuit
3.3V
DXP
V
DD
3.3V
DXP
3.3V
V
DD
T
REMOTE
TO SYSTEM
SHUTDOWN
C
S
DXN
µP
S1
S2
MAX6687
T
REMOTE
T
LOCAL
TO SYSTEM
SHUTDOWN
µP
C
S
DXN
S1
S2
MAX6688
12V
T
LOCAL
GND
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.
Local/Remote Temperature Switches in a
µMAX Package
MAX6687/MAX6688
ABSOLUTE MAXIMUM RATINGS
Voltages Referenced to GND
V
DD
, T
LOCAL
, T
REMOTE
............................................-0.3V to +6V
DXN .......................................................................-0.3V to +0.8V
All Other Pins..............................................-0.3V to (V
DD
+ 0.3V)
Input Current .........................................................................5mA
Output Current ....................................................................20mA
Continuous Power Dissipation (T
A
= +70°C)
8-Pin µMAX (derate 4.1mW/°C above +70°C) .............330mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +165°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
DD
= 3V to 5.5V, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
DD
= 3.3V and T
A
= +25°C.) (Note 1)
PARAMETER
Power-Supply Range
Average Supply Current
Supply Current During
Conversion
Power-On Reset (POR) Threshold
POR Threshold Hysteresis
Remote-Diode Temperature
Threshold Accuracy, Rising
Temperature
T
A
= +25°C, V
DD
= 3.3V
∆T
TH
T
A
= 0°C to +85°C, V
DD
= 3.3V
T
A
= -40°C to +125°C, V
DD
= 3.3V
Temperature trip thresholds from +40°C to
+105°C, V
DD
= 3.3V
Temperature trip thresholds +110°C and
+115°C, V
DD
= 3.3V
-1.5
-3.0
-5.0
-3.0
-3.5
5.0
0.6
V
OH
V
OL
V
IL
V
IH
1.8
10
V
OUT
= 5.5V, MAX6687
1
I
SOURCE
= 1mA, MAX6688
I
SINK
= 1mA
V
DD
- 0.2
0.2
0.4
POR
V
DD
falling edge
1
SYMBOL
V
DD
I
DD
CONDITION
MIN
3
215
400
1.5
50
+1.5
+3.0
+5.0
+3.0
°C
+3.5
°C
°C/V
V
V
V
V
µA
µA
°C
TYP
MAX
5.5
500
800
2.0
UNITS
V
µA
µA
V
mV
Internal Temperature Threshold
Accuracy, Rising Temperature
∆T
TH
Temperature Threshold
Hysteresis
Temperature Threshold Supply
Sensitivity
Output Voltage High
Output Voltage Low
Logic Input Low Voltage
(S1, S2)
Logic Input High Voltage
(S1, S2)
Input Current (S1, S2)
Open-Drain Output Leakage
Current
T
HYST
2
_______________________________________________________________________________________
Local/Remote Temperature Switches in a
µMAX Package
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= 3V to 5.5V, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
DD
= 3.3V and T
A
= +25°C.) (Note 1)
PARAMETER
Temperature Conversion Time
Temperature Sample Period
Current Sourcing for External
Diode
High level
Low level
SYMBOL
CONDITION
MIN
0.2
0.4
80
8
TYP
0.25
0.5
100
10
MAX
0.3
0.6
120
12
UNITS
s
s
µA
MAX6687/MAX6688
Note 1:
All parameters are tested at +25°C. Temperature specifications over a range of -40°C to +125°C are guaranteed by design.
Typical Operating Characteristics
(V
DD
= 3.3V, C
S
= 2200pF, T
A
= +25°C, unless otherwise noted.)
AVERAGE SUPPLY CURRENT
vs. AMBIENT TEMPERATURE
MAX6687/88 toc01
AVERAGE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6687/88 toc02
300
AVERAGE SUPPLY CURRENT (µA)
300
AVERAGE SUPPLY CURRENT (µA)
T
A
= +100°C
260
260
220
220
180
180
T
A
= -40°C
T
A
= +25°C
140
140
100
-50
-25
0
25
50
75
100
125
AMBIENT TEMPERATURE (°C)
100
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
TEMPERATURE TRIP THRESHOLD ERROR
vs. C
S
CAPACITANCE
MAX6687/88 toc03
REMOTE TEMPERATURE TRIP THRESHOLD
ERROR vs. AMBIENT TEMPERATURE
UPPER TRIP THRESHOLD ERROR (°C)
MAX6688U40H
T
REMOTE
TRIP = +125°C
MAX6687/88 toc04
TEMPERATURE TRIP THRESHOLD ERROR (°C)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1
MAX6688U40H
S1 = S2 = FLOAT
1
0
-1
-2
-3
-4
-5
10
C
S
CAPACITANCE (nF)
100
-50
-25
0
25
50
75
100
AMBIENT TEMPERATURE (°C)
_______________________________________________________________________________________
3
Local/Remote Temperature Switches in a
µMAX Package
MAX6687/MAX6688
Pin Description
PIN
MAX6687
1
2
3
MAX6688
1
2
3
NAME
V
DD
GND
DXP
FUNCTION
Power-Supply Input. Bypass to GND with a 0.1µF capacitor.
Ground
This pin connects to the positive (anode) terminal of the external P-N sense junction. It sources
current into the external junction. A 2200pF capacitor should be connected across DXP and
DXN.
This pin connects to the negative (cathode) terminal of the external P-N sense junction. It sinks
current from the external junction. A 2200pF capacitor should be connected across DXP and
DXN. DXN must be connected to the GND pin at the pin.
Open-Drain Active-Low Output. T
REMOTE
goes low when the temperature exceeds the factory-
programmed temperature threshold, either +120°C or +125°C. Connect a pullup resistor
(typically 10kΩ) between T
REMOTE
and a positive power supply up to 5.5V.
CMOS Push-Pull, Active-High Output. T
REMOTE
goes high when the temperature exceeds the
factory-programmed temperature threshold, either +120°C or +125°C.
Open-Drain Active-Low Output. T
LOCAL
goes low when the temperature exceeds the pin-
programmable temperature threshold set by S1 and S2. Connect a pullup resistor (typically
10kΩ) between T
LOCAL
and a positive power supply up to 5.5V.
CMOS Push-Pull, Active-High Output. T
LOCAL
goes high when the temperature exceeds the
pin-programmable temperature threshold set by S1 and S2.
Threshold Select Input. Used in conjunction with S2 to set the local threshold temperature
(Table 1). It can be connected to V
DD
, GND, or left floating.
Threshold Select Input. Used in conjunction with S1 to set the local threshold temperature
(Table 1). It can be connected to V
DD
, GND, or left floating.
4
4
DXN
5
—
T
REMOTE
—
5
T
REMOTE
6
—
T
LOCAL
—
7
8
6
7
8
T
LOCAL
S1
S2
Detailed Description
The MAX6687/MAX6688 sense the temperatures of
both a remote P-N junction and their own die. The
external P-N junction is typically a base-emitter junction
of a substrate PNP on a microprocessor, FPGA, or
ASIC die (see the
Typical Operating Circuit).
The remote temperature switch has a factory-pro-
grammed trip temperature of either +120°C or +125°C
and is intended to be used for system shutdown when
the die temperature of a remote IC, such as a micro-
processor, FPGA, or ASIC exceeds the factory-pro-
grammed thresholds.
The local temperature switch has a pin-programmable
threshold temperature (Table 1). This temperature
switch may be used for such functions as system shut-
down or for turning on a cooling fan when board tem-
perature exceeds the temperature limit. Two
temperature ranges are available for the local trip
threshold: +40°C to +80°C and +75°C to +115°C. S1
and S2 pins must be set to the desired trip temperature
before power is applied to the V
DD
pin. If S1 and S2
settings are changed after the power is turned on, the
local trip threshold remains set to the point where S1
and S2 were when power was applied.
Since the MAX6687/MAX6688 are often used for sys-
tem shutdown, they are designed so that the outputs
do not change on transient faults or when power is first
applied. This eliminates the possibility that the IC could
erroneously shut a system down.
The MAX6687/MAX6688 provide noise immunity by
integration and oversampling of the diode voltage, but
good design practice includes routing the DXP and
DXN lines away from noise sources, such as high-
speed digital lines, switching regulators, inductors, and
transformers. The DXP and DXN traces should be
paired together and surrounded by a ground plane
whenever possible.
4
_______________________________________________________________________________________
Local/Remote Temperature Switches in a
µMAX Package
MAX6687/MAX6688
Table 1. Local Temperature Trip Threshold Selection
S1
GND
GND
GND
FLOAT
FLOAT
FLOAT
V
DD
V
DD
V
DD
S2
GND
FLOAT
V
DD
GND
FLOAT
V
DD
GND
FLOAT
V
DD
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 V
BE
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.
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.
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
Chip Information
TRANSISTOR COUNT: 7765
PROCESS: BiCMOS
_______________________________________________________________________________________
5
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