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19-2636; Rev 1; 1/03
Local/Remote Temperature Switches in a MAX 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 transistor 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 factoryprogrammed trip temperature threshold of either +120C or +125C. The local temperature switch has a pin-programmable temperature threshold that is set by connecting pins S1 and S2 to ground, to VDD, or leaving them floating. Hysteresis for both local and remote thresholds is 5C. 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 outputs. TREMOTE asserts a logic signal when the remote temperature exceeds the factory-programmed +120C or +125C trip threshold. TLOCAL is asserted when the die temperature exceeds the pin-programmed threshold, which is controlled by pins S1 and S2. The local thresholds are available in two ranges in 5C increments. The two ranges are +40C to +80C and +75C to +115C. The MAX6687/MAX6688 operate from a 3.0V to 5.5V power supply and are available in a space-saving 8-pin MAX package.
Features
o Pin-Programmable Local Temperature Threshold in 5C Increments in Two Distinct Ranges: +40C to +80C and +75C to +115C o Factory-Programmed Remote Threshold: +120C (L Suffix) or +125C (H Suffix) o Open-Drain Active-Low Outputs (MAX6687) o CMOS Push-Pull, Active-High Outputs (MAX6688) o 1.5C Accuracy o 2Hz Temperature Sampling Rate o 215A Average Supply Current o 3.0V to 5.5V Power-Supply Voltage o 8-Pin MAX Package
MAX6687/MAX6688
Ordering Information
PART MAX6687UA40L MAX6687UA40H MAX6687UA75L MAX6687UA75H MAX6688UA40L MAX6688UA40H MAX6688UA75L MAX6688UA75H TEMP RANGE -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX
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 VDD 3.3V DXP 3.3V VDD TREMOTE TO SYSTEM SHUTDOWN
CS DXN P S1 S2
MAX6687
TREMOTE TLOCAL TO SYSTEM SHUTDOWN P
CS DXN S1 S2
MAX6688
12V
TLOCAL GND GND
N
________________________________________________________________ Maxim Integrated Products
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Local/Remote Temperature Switches in a MAX Package MAX6687/MAX6688
ABSOLUTE MAXIMUM RATINGS
Voltages Referenced to GND VDD, TLOCAL, TREMOTE ............................................-0.3V to +6V DXN .......................................................................-0.3V to +0.8V All Other Pins..............................................-0.3V to (VDD + 0.3V) Input Current .........................................................................5mA Output Current ....................................................................20mA Continuous Power Dissipation (TA = +70C) 8-Pin MAX (derate 4.1mW/C above +70C) .............330mW Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +165C Lead Temperature (soldering, 10s) .................................+300C
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
(VDD = 3V to 5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at VDD = 3.3V and TA = +25C.) (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 TA = +25C, VDD = 3.3V TTH TA = 0C to +85C, VDD = 3.3V TA = -40C to +125C, VDD = 3.3V Temperature trip thresholds from +40C to +105C, VDD = 3.3V Temperature trip thresholds +110C and +115C, VDD = 3.3V -1.5 -3.0 -5.0 -3.0 -3.5 5.0 0.6 VOH VOL VIL VIH 1.8 10 VOUT = 5.5V, MAX6687 1 ISOURCE = 1mA, MAX6688 ISINK = 1mA VDD - 0.2 0.2 0.4 POR VDD falling edge 1 SYMBOL VDD IDD 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 A A C TYP MAX 5.5 500 800 2.0 UNITS V A A V mV
Internal Temperature Threshold Accuracy, Rising Temperature
TTH
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
THYST
2
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Local/Remote Temperature Switches in a MAX Package
ELECTRICAL CHARACTERISTICS (continued)
(VDD = 3V to 5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at VDD = 3.3V and TA = +25C.) (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 A
MAX6687/MAX6688
Note 1: All parameters are tested at +25C. Temperature specifications over a range of -40C to +125C are guaranteed by design.
Typical Operating Characteristics
(VDD = 3.3V, CS = 2200pF, TA = +25C, 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 (A)
300 AVERAGE SUPPLY CURRENT (A) TA = +100C
260
260
220
220
180
180
TA = -40C TA = +25C
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. CS CAPACITANCE
MAX6687/88 toc03
REMOTE TEMPERATURE TRIP THRESHOLD ERROR vs. AMBIENT TEMPERATURE
UPPER TRIP THRESHOLD ERROR (C) MAX6688U40H TREMOTE TRIP = +125C
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 CS CAPACITANCE (nF)
100
-50
-25
0
25
50
75
100
AMBIENT TEMPERATURE (C)
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Local/Remote Temperature Switches in a MAX Package MAX6687/MAX6688
Pin Description
PIN MAX6687 1 2 3 MAX6688 1 2 3 NAME VDD GND DXP FUNCTION Power-Supply Input. Bypass to GND with a 0.1F 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. TREMOTE goes low when the temperature exceeds the factoryprogrammed temperature threshold, either +120C or +125C. Connect a pullup resistor (typically 10k) between TREMOTE and a positive power supply up to 5.5V. CMOS Push-Pull, Active-High Output. TREMOTE goes high when the temperature exceeds the factory-programmed temperature threshold, either +120C or +125C. Open-Drain Active-Low Output. TLOCAL goes low when the temperature exceeds the pinprogrammable temperature threshold set by S1 and S2. Connect a pullup resistor (typically 10k) between TLOCAL and a positive power supply up to 5.5V. CMOS Push-Pull, Active-High Output. TLOCAL 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 VDD, 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 VDD, GND, or left floating.
4
4
DXN
5
--
TREMOTE
--
5
TREMOTE
6
--
TLOCAL
-- 7 8
6 7 8
TLOCAL 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-programmed trip temperature of either +120C or +125C and is intended to be used for system shutdown when the die temperature of a remote IC, such as a microprocessor, FPGA, or ASIC exceeds the factory-programmed thresholds. The local temperature switch has a pin-programmable threshold temperature (Table 1). This temperature switch may be used for such functions as system shutdown or for turning on a cooling fan when board temperature exceeds the temperature limit. Two temperature ranges are available for the local trip
threshold: +40C to +80C and +75C to +115C. S1 and S2 pins must be set to the desired trip temperature before power is applied to the VDD 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 system 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 highspeed digital lines, switching regulators, inductors, and transformers. The DXP and DXN traces should be paired together and surrounded by a ground plane whenever possible.
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Local/Remote Temperature Switches in a MAX Package MAX6687/MAX6688
Table 1. Local Temperature Trip Threshold Selection
S1 GND GND GND FLOAT FLOAT FLOAT VDD VDD VDD S2 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 onchip temperature-sensing diodes. These on-chip diodes are substrate PNPs with their collectors grounded. Connect the base of the PNP to DXN and the emitter 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, usually small deviations in trip temperature thresholds.
should typically have a value of 2200pF. Larger capacitor values can cause temperature measurement errors. A 50% increase from the recommended capacitor value can cause up to 1C 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 heatgenerating 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 surrounding air temperature than they are to the temperature of their package leads, but they can be successfully used to respond to the ambient temperature 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
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Local/Remote Temperature Switches in a MAX Package MAX6687/MAX6688
Pin Configurations
TOP VIEW
VDD 1 GND DXP 2 8 7 S2 S1 TLOCAL TREMOTE VDD 1 GND DXP 2 8 7 S2 S1 TLOCAL TREMOTE
MAX6687
3 6 5 3 DXN 4 DXN 4
MAX6688
6 5
MAX
MAX
Functional Block Diagrams
VDD VDD
TREMOTE TREMOTE +120C OR +125C N TREMOTE +120C OR +125C DIGITAL DRIVER TREMOTE
DXP DXN
REMOTE TEMPERATURE CONVERTER
DXP
MAX6687
DXN LOCAL TEMPERATURE CONVERTER TLOCAL
REMOTE TEMPERATURE CONVERTER LOCAL TEMPERATURE CONVERTER
MAX6688
S1 TREMOTE +40C OR +115C S2 GND
N
S1 TREMOTE +40C OR +115C S2 GND
DIGITAL DRIVER
TLOCAL
Figure 1a. MAX6687 Functional Block Diagram
Figure 1b. MAX6688 Functional Block Diagram
Selector Guide
PART MAX6687UA40L MAX6687UA40H MAX6687UA75L MAX6687UA75H MAX6688UA40L MAX6688UA40H MAX6688UA75L MAX6688UA75H OUTPUTS Open drain, active low Open drain, active low Open drain, active low Open drain, active low Push pull, active high Push pull, active high Push pull, active high Push pull, active high REMOTE TRIP THRESHOLD (C) +120 +125 +120 +125 +120 +125 +120 +125 LOCAL TRIP THRESHOLD RANGE (C) +40 to +80 +40 to +80 +75 to +115 +75 to +115 +40 to +80 +40 to +80 +75 to +115 +75 to +115
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Local/Remote Temperature Switches in a MAX Package
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
8LUMAXD.EPS
MAX6687/MAX6688
4X S
8
8
INCHES DIM A A1 A2 b MIN 0.002 0.030 MAX 0.043 0.006 0.037
MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95
y 0.500.1
E
H
0.60.1
c D e E H L
1
1
0.60.1
S
D
BOTTOM VIEW
0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.188 0.026 0.016 6 0 0.0207 BSC
0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0 6 0.5250 BSC
TOP VIEW
A2
A1
A
c e b L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0036
1 1
J
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 7 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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