MAXIM MAX6685, MAX6686 Technical data

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 (T

HIGH

and T

LOW

). T

HIGH

asserts a logic signal when the remote
temperature crosses the factory-programmed, +120°C, or
+125°C upper trip threshold. T

LOW

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 5°C increments. The two ranges
are +40°C to +80°C and +75°C to +115°C. Hysteresis for
both outputs to be deasserted is typically 5°C.

T

HIGH

is an open-drain, active-low output for both the

MAX6685 and the MAX6686. T

LOW

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 µMAX package.

Applications

Features

♦ Pin-Programmed Lower Temperature Threshold

from +40°C to +80°C or +75°C to +115°C
(5°C Increments)

♦ Preset Upper Threshold: +120°C or +125°C

♦ Open-Drain, Active-Low Output for Upper

Temperature Alarm

♦ CMOS Push-Pull, Active-High or Open-Drain,

Active-Low Output for Lower Temperature Alarm

♦ 1.5°C Accuracy

♦ 3.0V to 5.5V, 200µA Supply

♦ 8-Pin µMAX Package

MAX6685/MAX6686

Dual-Output Remote-Junction

Temperature Switches

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

MAX6685

C

S

12V

GND

CPU

S1

DXN

S2

3.3V

TO SYSTEM
SHUTDOWN

N

T

LOW

DXP

V

DD

T

HIGH

MAX6686

C

S

GND

CPU

S1

DXN

S2

3.3V

TO SYSTEM
SHUTDOWN

TO CLOCK
THROTTLE

CONTROL

T

LOW

DXP

V

DD

T

HIGH

Typical Operating Circuits

19-2459; Rev 2; 4/03

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.

Pin Configurations appear at end of data sheet.

CPU Temperature
Protection

Fan Control

Multichip Modules
FPGA Temperature

Protection

T

PART

MAX6685AU40L Push-pull, active high +40°C to +80°C +120°C 8 µMAX

MAX6685AU40H Push-pull, active high +40°C to +80°C +125°C 8 µMAX

MAX6685AU75L Push-pull, active high +75°C to +115°C +120°C 8 µMAX

MAX6685AU75H Push-pull, active high +75°C to +115°C +125°C 8 µMAX

MAX6686AU40L Open drain, active low +40°C to +80°C +120°C 8 µMAX

MAX6686AU40H Open drain, active low +40°C to +80°C +125°C 8 µMAX

MAX6686AU75L Open drain, active low +75°C to +115°C +120°C 8 µMAX

MAX6686AU75H Open drain, active low +75°C to +115°C +125°C 8 µMAX

LOW

OUTPUT

TRIP

T

LOW

RANGE (0°C)

T

TRIP

HIGH

THRESHOLD (0°C)

PIN-PACKAGE

MAX6685/MAX6686

Dual-Output Remote-Junction
Temperature Switches

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VDD= 3.0V to 5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VDD= 3.3V and TA= +25°C.) (Note 1)

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.

Voltages Referenced to GND
V

DD, TLOW

, T

HIGH

.....................................................-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

Note 1: All parameters are tested at +25°C. Temperature specifications over a range of -40°C to +125°C are guaranteed by design.
Note 2: T

RJ

is the temperature of the remote-sensing diode junction.

Power-Supply Range V

Average Supply Current I

Supply Current During
Conversion

Power-On Reset Threshold POR V

POR Threshold Hysteresis 50 mV

Temperature Threshold
Accuracy

Temperature Threshold
Hysteresis

Supply Sensitivity of Temperature
Threshold

Output Voltage High V

Output Voltage Low V

Logic-Low Input Voltage V

Logic-High Input Voltage V

Input Current S1, S2 10 µA

Open-Drain Output Leakage
Current

Conversion Time 0.09 0.11 0.13 s

Sample Period 0.35 0.45 0.55 s

Current Sourcing for External
Diode

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS

DD

DD

falling edge 1.0 1.5 2.0 V

DD

VDD = 3.3V, TA = +25°C, TRJ = 0°C to +125°C

∆T

T

HYST

(Note 2)

TH

TA = 0°C to +100°C, TRJ = 0°C to +125°C 2.0

TA = +25°C, TRJ = 0°C to +125°C,
V

= 3.0V to 5.5V

DD

OHISOURCE

OLISINK

S1, S2 0.4 V

IL

S1, S2 1.8 V

IH

V

High level 80 100 120

Low level 8 10 12

= 1mA, MAX6685 T

= 1mA 0.2 V

OUT

= 5.5V, T

LOW

and T

HIGH

LOW

only

3.0 5.5 V

200 500 µA

400 800 µA

-1.5 +1.5

5.0 °C

0.6 °C/V

V

-

DD

0.2

1µA

°C

V

µA

MAX6685/MAX6686

Dual-Output Remote-Junction

Temperature Switches

_______________________________________________________________________________________ 3

Typical Operating Characteristics

(VDD= 3.3V, CS= 2200pF, TA= +25°C, unless otherwise noted. See Typical Operating Circuits.)

AVERAGE SUPPLY CURRENT

vs. AMBIENT TEMPERATURE

200

180

160

140

120

AVERAGE SUPPLY CURRENT (µA)

100

-50 125
AMBIENT TEMPERATURE (°C)

UPPER TEMPERATURE TRIP THRESHOLD

2.0

1.6

1.2

0.8

0.4

0

-0.4

-0.8

-1.2

UPPER TRIP THRESHOLD ERROR (°C)

-1.6

-2.0

-50 125

250

MAX6685 toc01

200

150

100

AVERAGE SUPPLY CURRENT (µA)

1007550250-25

ERROR vs. AMBIENT TEMPERATURE

MAX6685U40H

TRIP = +125°C

T

HIGH

AMBIENT TEMPERATURE (°C)

AVERAGE SUPPLY CURRENT

vs. SUPPLY VOLTAGE

50

0

3.0 5.5
SUPPLY VOLTAGE (V)

5.04.54.03.5

LOWER TEMPERATURE TRIP THRESHOLD

ERROR vs. AMBIENT TEMPERATURE

2.0

MAX6685U40H

1.6

MAX6685 toc04

1007525 500-25

S1 = S2 = V

1.2

0.8

0.4

0

-0.4

-0.8

-1.2

LOWER TRIP THRESHOLD ERROR (°C)

-1.6

-2.0

-50 125

10

MAX6685 toc02

TEMPERATURE TRIP THRESHOLD ERROR (°C)

DD

AMBIENT TEMPERATURE (°C)

TEMPERATURE TRIP THRESHOLD ERROR

MAX6685U40H
S1 = S2 = GND

8

6

4

2

0

060

1007525 500-25

CAPACITANCE

vs. C

S

CS CAPACITANCE (nF)

MAX6685 toc05

MAX6685 toc03

5040302010

MAX6685/MAX6686

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 5°C 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 +120°C or
+125°C. The lower temperature thresholds are pin pro­grammable in 5°C increments (Table 1). Two tempera-

ture ranges are available for the lower 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 VDDpin. 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
V

be

characteristics. Always use a transistor for the sens-

ing junction; diodes do not work.

Dual-Output Remote-Junction
Temperature Switches

4 _______________________________________________________________________________________

Pin Description

PIN

MAX6685 MAX6686

11VDDPower-Supply Input. Bypass to GND with a 0.1µF capacitor.

2 2 GND Ground

3 3 DXP

4 4 DXN

55T

6—T

—6T

77S1

88S2

NAME FUNCTION

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. T
programmed upper temperature threshold, either +120°C or +125°C. Connect a pullup resistor

HIGH

(typically 10kΩ) between T

CMOS Push-Pull, Active-High Output. T

LOW

programmed lower temperature threshold.

Open-Drain, Active-Low Output. T
programmed lower temperature threshold. Connect a pullup resistor (typically 10kΩ) between

LOW

T

and a positive supply up to 5.5V.

LOW

Threshold Select Input. Used in conjunction with S2 to set the lower threshold for T
It can be connected to V

Threshold Select Input. Used in conjunction with S1 to set the lower threshold for T
It can be connected to V

goes low when the temperature exceeds the factory-

HIGH

and a positive supply up to 5.5V.

HIGH

goes HIGH when the temperature exceeds the pin-

LOW

goes LOW when the temperature exceeds the pin-

LOW

, GND, or left floating.

DD

, GND, or left floating.

DD

(Table 1).

LOW

(Table 1).

LOW

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 ±1°C error.

MAX6685/MAX6686

Dual-Output Remote-Junction

Temperature Switches

_______________________________________________________________________________________ 5

Figure 1. MAX6685 Functional Diagram

Figure 2. MAX6686 Functional Diagram

MAX6685AUA40L
MAX6685AUA40H
MAX6686AUA40L
MAX6686AUA40H

MAX6685AUA75L
MAX6685AUA75H
MAX6686AUA75L
MAX6686AUA75H

S1 S2

LOWER TEMPERATURE

TRIP THRESHOLD (°C)

LOWER TEMPERATURE

TRIP THRESHOLD (°C)

GND GND +40 +75

GND FLOAT +45 +80

GND V

DD

+50 +85

FLOAT GND +55 +90

FLOAT FLOAT +60 +95

FLOAT V

DD

+65 +100

V

DD

GND +70 +105

V

DD

FLOAT +75 +110

V

DD

V

DD

+80 +115

Table 1. Lower Temperature Trip Threshold Selection

Table 2. Sensor Transistor Manufacturers

Note: Discrete transistors must be diode connected (base

shorted to collector).

Central Semiconductor (USA) CMPT3904

ON Semiconductor (USA) 2N3904, 2N3906

Rohm Semiconductor (Japan) SST3904

Samsung (Korea) KST3904-TF

Siemens (Germany) SMBT3904

MANUFACTURER MODEL NO.

V

DD

T

HIGH

+120°C OR +125°C

DXP

DXN

S1

S2

REMOTE

TEMPERATURE

CONVERTER

T

LOW

+40°C TO +115°C

GND

DIGITAL
DRIVER

MAX6685

T

HIGH

N

T

LOW

DXP

DXN

S1

S2

T

HIGH

+120°C OR +125°C

REMOTE

TEMPERATURE

CONVERTER

T

LOW

+40°C TO +115°C

V

DD

GND

MAX6686

T

HIGH

N

T

LOW

N

MAX6685/MAX6686

Dual-Output Remote-Junction
Temperature Switches

6 _______________________________________________________________________________________

Pin Configurations

Chip Information

TRANSISTOR COUNT: 7765

PROCESS: BiCMOS

TOP VIEW

V

DXP

DXN

1

DD

2

MAX6685

3

4

µMAX

87S2

6

5

1

V

DD

S1GND

T

LOW

T

HIGH

DXP

DXN

2

MAX6686

3

4

µMAX

87S2

6

5

S1GND

T

LOW

T

HIGH

MAX6685/MAX6686

Dual-Output Remote-Junction

Temperature Switches

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

© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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

.)

b

E H

A1

4X S

BOTTOM VIEW

A

c

L

SIDE VIEW

8

1

DIM

A
A1
A2
b

c
D
e

E

H

L

α

S

INCHES

MIN

-

0.002

0.030

0.010

0.005

0.116

0.0256 BSC

0.116

0.188

0.016
0∞

0.0207 BSC

0.037

0.007

0.198

0.026

MAX

0.043

0.006

0.014

0.120

0.120

6∞

MILLIMETERS

0.05 0.15

0.25 0.36

0.13 0.18

2.95 3.05

2.95 3.05

4.78

0.41

MIN

- 1.10

0.65 BSC

0.5250 BSC

MAX

0.950.75

5.03

0.66

8LUMAXD.EPS

6∞0∞

α

8

ÿ 0.50±0.1

0.6±0.1

0.6±0.1

1

D

TOP VIEW

A2

e

FRONT VIEW

PROPRIETARY INFORMATION

TITLE:

PACKAGE OUTLINE, 8L uMAX/uSOP

REV.DOCUMENT CONTROL NO.APPROVAL

21-0036

1

J

1