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19-2459; Rev 2; 4/03
Dual-Output Remote-Junction Temperature Switches
General Description
MAX6685/MAX6686 are dual-output temperature switches that use an external diode-connected transistor as a sensing element. These devices have two logic outputs (THIGH and TLOW). THIGH asserts a logic signal when the remote temperature crosses the factory-programmed, +120C, or +125C upper trip threshold. TLOW is asserted when the remote temperature exceeds the lower threshold, which is controlled by pins S1 and S2. The lower thresholds are available in two ranges in 5C increments. The two ranges are +40C to +80C and +75C to +115C. Hysteresis for both outputs to be deasserted is typically 5C. THIGH is an open-drain, active-low output for both the MAX6685 and the MAX6686. TLOW is a CMOS push-pull, active-high output for the MAX6685 and is an open-drain, active-low output for the MAX6686. They are available in a space-saving 8-pin MAX package.
Features
o Pin-Programmed Lower Temperature Threshold from +40C to +80C or +75C to +115C (5C Increments) o Preset Upper Threshold: +120C or +125C o Open-Drain, Active-Low Output for Upper Temperature Alarm o CMOS Push-Pull, Active-High or Open-Drain, Active-Low Output for Lower Temperature Alarm o 1.5C Accuracy o 3.0V to 5.5V, 200A Supply o 8-Pin MAX Package
MAX6685/MAX6686
Applications
CPU Temperature Protection Fan Control Multichip Modules FPGA Temperature Protection
Pin Configurations appear at end of data sheet.
Ordering Information
PART MAX6685AU40L MAX6685AU40H MAX6685AU75L MAX6685AU75H MAX6686AU40L MAX6686AU40H MAX6686AU75L MAX6686AU75H TLOW OUTPUT Push-pull, active high Push-pull, active high Push-pull, active high Push-pull, active high Open drain, active low Open drain, active low Open drain, active low Open drain, active low TLOW TRIP RANGE (0C) +40C to +80C +40C to +80C +75C to +115C +75C to +115C +40C to +80C +40C to +80C +75C to +115C +75C to +115C THIGH TRIP THRESHOLD (0C) +120C +125C +120C +125C +120C +125C +120C +125C PIN-PACKAGE 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX
Typical Operating Circuits
3.3V VDD TO SYSTEM SHUTDOWN THIGH 12V CPU CS DXN S1 TLOW GND N S2 GND TLOW DXP 3.3V VDD
CPU CS
DXP
THIGH
TO SYSTEM SHUTDOWN
MAX6685
DXN S1 S2
MAX6686
TO CLOCK THROTTLE CONTROL
________________________________________________________________ Maxim Integrated Products
1
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Dual-Output Remote-Junction Temperature Switches MAX6685/MAX6686
ABSOLUTE MAXIMUM RATINGS
Voltages Referenced to GND VDD, TLOW, THIGH .....................................................-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 = 3.0V 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 Threshold POR Threshold Hysteresis Temperature Threshold Accuracy Temperature Threshold Hysteresis Supply Sensitivity of Temperature Threshold Output Voltage High Output Voltage Low Logic-Low Input Voltage Logic-High Input Voltage Input Current Open-Drain Output Leakage Current Conversion Time Sample Period Current Sourcing for External Diode High level Low level VOH VOL VIL VIH TTH VDD = 3.3V, TA = +25C, TRJ = 0C to +125C (Note 2) TA = 0C to +100C, TRJ = 0C to +125C THYST TA = +25C, TRJ = 0C to +125C, VDD = 3.0V to 5.5V ISOURCE = 1mA, MAX6685 TLOW only ISINK = 1mA S1, S2 S1, S2 S1, S2 VOUT = 5.5V, TLOW and THIGH 0.09 0.35 80 8 0.11 0.45 100 10 1.8 10 1 0.13 0.55 120 12 VDD 0.2 0.2 0.4 -1.5 2.0 5.0 0.6 C C/V V V V V A A s s A POR VDD falling edge 1.0 SYMBOL VDD IDD CONDITION MIN 3.0 200 400 1.5 50 +1.5 TYP MAX 5.5 500 800 2.0 UNITS V A A V mV C
Note 1: All parameters are tested at +25C. Temperature specifications over a range of -40C to +125C are guaranteed by design. Note 2: TRJ is the temperature of the remote-sensing diode junction.
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Dual-Output Remote-Junction Temperature Switches
Typical Operating Characteristics
(VDD = 3.3V, CS = 2200pF, TA = +25C, unless otherwise noted. See Typical Operating Circuits.)
AVERAGE SUPPLY CURRENT vs. AMBIENT TEMPERATURE
MAX6685 toc01
MAX6685/MAX6686
AVERAGE SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX6685 toc02
TEMPERATURE TRIP THRESHOLD ERROR vs. CS CAPACITANCE
TEMPERATURE TRIP THRESHOLD ERROR (C) MAX6685U40H S1 = S2 = GND 8
MAX6685 toc03
200 AVERAGE SUPPLY CURRENT (A)
250 AVERAGE SUPPLY CURRENT (A)
10
180
200
160
150
6
140
100
4
120
50
2
100 -50 -25 0 25 50 75 100 125 AMBIENT TEMPERATURE (C)
0 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
0 0 10 20 30 40 50 60 CS CAPACITANCE (nF)
UPPER TEMPERATURE TRIP THRESHOLD ERROR vs. AMBIENT TEMPERATURE
MAX6685 toc04
LOWER TEMPERATURE TRIP THRESHOLD ERROR vs. AMBIENT TEMPERATURE
LOWER TRIP THRESHOLD ERROR (C) 1.6 1.2 0.8 0.4 0 -0.4 -0.8 -1.2 -1.6 -2.0 MAX6685U40H S1 = S2 = VDD
MAX6685 toc05
2.0 UPPER TRIP THRESHOLD ERROR (C) 1.6 1.2 0.8 0.4 0 -0.4 -0.8 -1.2 -1.6 -2.0 -50 -25 0 25 50 75 100 MAX6685U40H THIGH TRIP = +125C
2.0
125
-50
-25
0
25
50
75
100
125
AMBIENT TEMPERATURE (C)
AMBIENT TEMPERATURE (C)
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Dual-Output Remote-Junction Temperature Switches MAX6685/MAX6686
Pin Description
PIN MAX6685 MAX6686 1 2 3 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 with the shortest possible connection. Open-Drain, Active-Low Output. THIGH goes low when the temperature exceeds the factoryprogrammed upper temperature threshold, either +120C or +125C. Connect a pullup resistor (typically 10k) between THIGH and a positive supply up to 5.5V. CMOS Push-Pull, Active-High Output. TLOW goes HIGH when the temperature exceeds the pinprogrammed lower temperature threshold. Open-Drain, Active-Low Output. TLOW goes LOW when the temperature exceeds the pinprogrammed lower temperature threshold. Connect a pullup resistor (typically 10k) between TLOW and a positive supply up to 5.5V. Threshold Select Input. Used in conjunction with S2 to set the lower threshold for TLOW (Table 1). It can be connected to VDD, GND, or left floating. Threshold Select Input. Used in conjunction with S1 to set the lower threshold for TLOW (Table 1). It can be connected to VDD, GND, or left floating.
4
4
DXN
5
5
THIGH
6
--
TLOW
--
6
TLOW
7 8
7 8
S1 S2
Detailed Description
The MAX6685/MAX6686 dual-output remote-sensing junction temperature switches incorporate a precision remote-junction temperature sensor and two comparators. These devices use an external P-N junction as the temperature-sensing element (see Typical Operating Circuits). The MAX6685/MAX6686 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. The 5C hysteresis keeps the outputs from "chattering" when the measured temperature is close to the threshold temperature. The MAX6685/MAX6686 are available with preset upper temperature thresholds of +120C or +125C. The lower temperature thresholds are pin programmable in 5C increments (Table 1). Two tempera-
ture ranges are available for the lower 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 this is done after the power is turned on, the lower trip threshold remains set to the point where S1 and S2 were when power was applied.
Applications Information
Remote-Diode Selection
The MAX6685/MAX6686 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 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 Vbe characteristics. Always use a transistor for the sensing junction; diodes do not work.
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Dual-Output Remote-Junction Temperature Switches MAX6685/MAX6686
Table 1. Lower Temperature Trip Threshold Selection
MAX6685AUA40L MAX6685AUA40H MAX6686AUA40L MAX6686AUA40H LOWER TEMPERATURE TRIP THRESHOLD (C) GND GND GND FLOAT FLOAT FLOAT VDD VDD VDD GND FLOAT VDD GND FLOAT VDD GND FLOAT VDD +40 +45 +50 +55 +60 +65 +70 +75 +80 MAX6685AUA75L MAX6685AUA75H MAX6686AUA75L MAX6686AUA75H LOWER TEMPERATURE TRIP THRESHOLD (C) +75 +80 +85 +90 +95 +100 +105 +110 +115
S1
S2
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 capacitor values can cause temperature measurement errors. A 50% variation from the recommended capacitor value can cause up to 1C error.
Table 2. Sensor Transistor Manufacturers
MANUFACTURER Central Semiconductor (USA) ON Semiconductor (USA) Rohm Semiconductor (Japan) Samsung (Korea) Siemens (Germany) MODEL NO. CMPT3904 2N3904, 2N3906 SST3904 KST3904-TF SMBT3904
Note: Discrete transistors must be diode connected (base shorted to collector).
VDD
VDD
THIGH +120C OR +125C N DXP DXN REMOTE TEMPERATURE CONVERTER DIGITAL DRIVER
THIGH
THIGH +120C OR +125C N DXP DXN REMOTE TEMPERATURE CONVERTER N TLOW +40C TO +115C
THIGH
TLOW
S1 S2
TLOW
TLOW +40C TO +115C
S1 S2
GND
MAX6685
GND
MAX6686
Figure 1. MAX6685 Functional Diagram
Figure 2. MAX6686 Functional Diagram 5
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Dual-Output Remote-Junction Temperature Switches MAX6685/MAX6686
Pin Configurations Chip Information
TRANSISTOR COUNT: 7765 PROCESS: BiCMOS
TOP VIEW
VDD 1 GND DXP 2
8 7
S2 S1 TLOW THIGH
VDD 1 GND DXP 2
8 7
S2 S1 TLOW THIGH
MAX6685
3 6 5 3 DXN 4 DXN 4
MAX6686
6 5
MAX
MAX
6
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Dual-Output Remote-Junction Temperature Switches
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
MAX6685/MAX6686
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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