MAXIM MAX6657, MAX6658, MAX6659 Technical data

General Description

The MAX6657/MAX6658/MAX6659 are precise, two­channel digital temperature sensors. Each accurately
measures the temperature of its own die and one
remote PN junction, and reports the temperature in digi­tal form on a 2-wire serial interface. The remote junction
can be a diode-connected transistor like the low-cost
NPN type 2N3904 or 2N3906 PNP type. The remote
junction can also be a common-collector PNP, such as
a substrate PNP of a microprocessor.

The 2-wire serial interface accepts standard System
Management Bus (SMBus™) commands such as Write
Byte, Read Byte, Send Byte, and Receive Byte to read
the temperature data and program the alarm thresholds
and conversion rate. The MAX6657/MAX6658/
MAX6659 can function autonomously with a program­mable conversion rate, which allows the control of sup­ply current and temperature update rate to match
system needs. For conversion rates of 4Hz or less, the
temperature is represented in extended mode as 10
bits + sign with a resolution of 0.125°C. When the con­version rate is faster than 4Hz, output data is 7 bits +
sign with a resolution of 1°C. The MAX6657/
MAX6658/MAX6659 also include an SMBus timeout
feature to enhance system reliability.

Remote accuracy is ±1°C between +60°C and +100°C
with no calibration needed. The MAX6657 measures
temperatures from 0°C to +125°C and the MAX6658/
MAX6659 from -55°C to +125°C. The MAX6659 has the
added benefit of being able to select one of three
addresses through an address pin, and a second over­temperature alarm pin for greater system reliability.

Applications

Desktop Computers Workstations
Notebook Computers
Servers

Features

o Dual Channel Measures Remote and Local

Temperature

o 11-Bit, +0.125°C Resolution

o High Accuracy ±1°C (max) from +60°C to +100°C

(Remote)

o No Calibration Required

o Programmable Under/Overtemperature Alarms

o Programmable Conversion Rate

(0.0625Hz to 16Hz)

o SMBus/I

2

C-Compatible Interface

o Two Alarm Outputs: ALERT and OVERT1

(MAX6657 and MAX6658)

o Three Alarm Outputs: ALERT, OVERT1,

and OVERT2 (MAX6659)

o Compatible with 65nm Process Technology

(Y Versions)

MAX6657/MAX6658/MAX6659

±1°C, SMBus-Compatible Remote/Local Temperature

Sensors with Overtemperature Alarms

________________________________________________________________

Maxim Integrated Products

1

19-2034; Rev 5; 10/10

Ordering Information

SMBus is a trademark of Intel Corp.

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

V

CC

N.C.

STBY

SMBCLK

N.C.

SMBDATA

N.C.

OVERT2

ALERT

TOP VIEW

MAX6659

QSOP

N.C.

DXP

OVERT1

DXN

ADD

GND

GND

ALERT

GNDOVERT1

1

2

87SMBCLK

SMBDATADXP

DXN

V

CC

SO

3

4

6

5

MAX6657
MAX6658

Pin Configurations

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.

Typical Operating Circuit appears at the end of the data
sheet.

Ordering Information continued at end of data sheet.

Note: All devices are specified over the -55°C to +125°C oper-

ating temperature range.

+

Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

PART

MAX6657MSA 0°C to +125°C 8 SO

MAX6657MSA+ 0°C to +125°C 8 SO

MAX6657MSA-T 0°C to +125°C 8 SO

MAX6657MSA+T 0°C to +125°C 8 SO

MAX6657YMSA+ 0°C to +125°C 8 SO

MAX6657YMSA+T 0°C to +125°C 8 SO

MEASURED TEMP

RANGE

PIN-PACKAGE

MAX6657/MAX6658/MAX6659

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

(All voltages referenced to GND.)
V

CC

..........................................................................-0.3V to +6V

DXP ............................................................-0.3V to (V

CC

+ 0.3V)

DXN ......................................................................-0.3V to +0.8V

SMBCLK, SMBDATA, ALERT, OVERT1,

OVERT2 ..............................................................-0.3V to +6V

SMBDATA, ALERT, OVERT1, OVERT2

Current ..........................................................-1mA to +50mA

DXN Current ......................................................................±1mA

Continuous Power Dissipation (T

A

= +70°C)

8-Pin SO (derate 5.9mW/°C above +70°C) .................471mW

16-Pin QSOP (derate 8.3mW/°C above +70°C) ..........664mW

Junction Temperature .....................................................+150°C

Storage Temperature Range ............................-65°C to +150°C

Lead Temperature (soldering, 10s) ................................+300°C

Soldering Temperature (reflow)

Lead(Pb)-free ..............................................................+260°C

Containing lead(Pb) ....................................................+240°C

ELECTRICAL CHARACTERISTICS

(VCC= +3.0V to +5.5V, TA= 0°C to +125°C, unless otherwise specified. Typical values are at VCC= +3.3V and TA= +25°C.)

±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Temperature Resolution,
Legacy Mode

Temperature Resolution,
Extended Mode

TRJ = +60°C to +100°C, VCC = +3.3V

Remote Temperature Error
(MAX6657, MAX6657Y)

Local Temperature Error
(MAX6657)

Remote Temperature Error
(MAX6658/MAX6659/
MAX6658Y/MAX6659Y)

Local Temperature Error
(MAX6658/MAX6659)

Local Temperature Error
(MAX665_Y)

Line Regulation 3.0V ≤ VCC ≤ 5.5V 0.2 0.6 m°C/V

Supply Voltage Range V

Undervoltage Lockout Threshold UVLO Falling edge of VCC disables ADC 2.60 2.80 2.95 V

Undervoltage Lockout Hysteresis 90 mV

Power-On Reset (POR) Threshold VCC, falling edge 1.5 2.0 2.5 V

POR Threshold Hysteresis 90 mV

Standby Supply Current SMBus static 3 10 µA

Operating Current During conversion 0.5 1.0 mA

(Note 1)

TRJ = 0°C to +100°C, VCC = +3.3V (Note 1) -3.0 +3.0

= 0°C to +125°C, VCC = +3.3V (Note 1) -5.0 +5.0

T

RJ

TA = +60°C to +100°C, VCC = +3.3V -2.0 +2.0

TA = 0°C to +100°C, VCC = +3.3V -3.0 +3.0

= 0°C to +125°C, VCC = +3.3V -5.0 +5.0

T

A

TRJ = +60°C to +100°C, VCC = +3.3V
(Note 1)

TRJ = 0°C to +100°C, VCC = +3.3V (Note 1) -3.0 3.0

T

= -55°C to +125°C, VCC = +3.3V (Note 1) -5.0 +5.0

RJ

TA = +60°C to +100°C, VCC = +3.3V -2.0 +2.0

TA = 0°C to +100°C, VCC = +3.3V -3.0 +3.0

= -55°C to +125°C, VCC = +3.3V (Note 2) -5.0 +5.0

T

A

TA = +60°C to +100°C, VCC = +3.3V -3.8

TA = 0°C to +100°C, VCC = +3.3V -4.0

T

= 0°C to +125°C, VCC = +3.3V -4.4

A

CC

1°C

8 Bits

0.125 °C

11 Bits

-1.0 +1.0

-1.0 1.0

3.0 5.5 V

°C

°C

°C

°C

°C

MAX6657/MAX6658/MAX6659

_______________________________________________________________________________________ 3

Note 1: TA= +25°C to +85°C.
Note 2: If both the local and the remote junction are below T

A

= -20°C, then VCC> 3.15V.

Note 3: For conversion rates of 4Hz or slower, the conversion time doubles.
Note 4: Timing specifications guaranteed by design.
Note 5: The serial interface resets when SMBCLK is low for more than t

TIMEOUT

.

Note 6: A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SMBCLK's falling edge.

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +3.0V to +5.5V, TA= 0°C to +125°C, unless otherwise specified. Typical values are at VCC= +3.3V and TA= +25°C.)

±1°C, SMBus-Compatible Remote/Local Temperature

Sensors with Overtemperature Alarms

Average Operating Current

SMBus-COMPATIBLE INTERFACE (SMBCLK, SMBDATA, STBY)

SMBus-COMPATIBLE TIMING (Note 4)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

0.25 conversions/s 40 70

2 conversions/s 150 250

Conversion Time t

Conversion Timing Error ±25 %

DXP and DXN Leakage Current In standby mode 100 nA

Remote-Diode Source Current I

(ALERT, OVERT)

Output Low Sink Current

Output High Leakage Current VOH = 5.5V 1 µA

Logic Input Low Voltage V

Logic Input High Voltage V

Input Leakage Current I

Output Low Sink Current I

Input Capacitance C

Serial-Clock Frequency f

Bus Free Time Between STOP
and START Condition

START Condition Setup Time 4.7 µs

Repeat START Condition Setup
Time

START Condition Hold Time t

STOP Condition Setup Time t

Clock Low Period t

Clock High Period t

Data Setup Time t

Receive SCL/SDA Rise Time t

Receive SCL/SDA Fall Time t

Pulse Width of Spike Suppressed t

SMBus Timeout SMBDATA low period for interface reset 25 37 45 ms

CONV

LEAK

SCL

t

BUF

t

SU:STA

HD:STA

SU:STO

LOW

HIGH

HD:DAT

From stop bit to conversion completed
(Note 4)

High level 80 100 120

RJ

Low level 8 10 12

VOL = 0.4V 1

V

= 0.6V 6

OL

IL

VCC = +3.0V 2.2

IH

VCC = +5.5V 2.4

VIN = V

VOL = 0.6V 6 mA

OL

IN

(Note 5) 100 kHz

90% to 90% 50 ns

10% of SMBDATA to 90% of SMBCLK 4 µs

90% of SMBCLK to 90% of SMBDATA 4 µs

10% to 10% 4.7 µs

90% to 90% 4 µs

(Note 6) 0 µs

R

F

SP

GND

or V

CC

95 125 156 ms

0.8 V

±1 µA

5pF

4.7 µs

1µs

300 ns

050ns

µA

µA

mA

V

MAX6657/MAX6658/MAX6659

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VCC= +3.3V, TA= +25°C, unless otherwise noted.)

4.5

4.0

3.5

3.0

2.5

3.0 4.03.5 4.5 5.0 5.5

STANDBY SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX6657 toc01

SUPPLY VOLTAGE (V)

STANDBY SUPPLY CURRENT (µA)

0.063 0.5 10.125 0.25 2 4 8 16

OPERATING SUPPLY CURRENT

vs. CONVERSION RATE

MAX6657 toc02

CONVERSION RATE (Hz)

OPERATING SUPPLY CURRENT (µA)

0

200

400

600

8Hz AND 16Hz ARE 1°C RESOLUTION

-3

-2

-1

0

1

2

3

-55 -5-30 20 45 70 95 120

MAX6659

REMOTE TEMPERATURE ERROR

vs. REMOTE-DIODE TEMPERATURE

MAX6657 toc03

TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

FAIRCHILD 2N3906

-3

-2

-1

0

1

2

3

-55 -5-30 20 45 70 95 120

LOCAL TEMPERATURE ERROR

vs. DIE TEMPERATURE

MAX6657 toc04

TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

1

0

-1

-2

-3
10k 1M100k 10M 100M

TEMPERATURE ERROR vs.

POWER-SUPPLY NOISE FREQUENCY

MAX6657 toc05

FREQUENCY (Hz)

TEMPERATURE ERROR (°C)

VIN = SQUARE WAVE APPLIED TO V

CC

WITH NO 0.1µF VCC CAPACITOR

1

0

-1

-2

-3

0.01k 100k1k 10M 1G

TEMPERATURE ERROR vs.

COMMON-MODE NOISE FREQUENCY

MAX6657 toc06

FREQUENCY (Hz)

TEMPERATURE ERROR (°C)

VIN = AC-COUPLED TO DXN
V

IN

= 100mVp-p

1

0

-1

-2

-3
10k 1M100k 10M 100M

TEMPERATURE ERROR vs.

DIFFERENTIAL-MODE NOISE FREQUENCY

MAX6657 toc07

FREQUENCY (Hz)

TEMPERATURE ERROR (°C)

VIN = 10mV

P-P

SQUARE WAVE

APPLIED TO DXP-DXN

-5

-4

-3

-2

-1

0

0405020 3010 60 70 80 90 100

TEMPERATURE ERROR vs.

DXP-DXN CAPACITANCE

MAX6657 toc08

DXP-DXN CAPACITANCE (nF)

TEMPERATURE ERROR (°C)

±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms

MAX6657/MAX6658/MAX6659

_______________________________________________________________________________________ 5

Pin Description

±1°C, SMBus-Compatible Remote/Local Temperature

Sensors with Overtemperature Alarms

PIN

MAX6657
MAX6658

11V

2 3 DXP

34DXN

46OVERT1

5 7, 8 GND Ground

69ALERT

7 12 SMBDATA SMBus Serial-Data Input/Output, Open-Drain

8 14 SMBCLK SMBus Serial-Clock Input

— 5 ADD

—10OVERT2

—15STBY

— 2, 11, 13, 16 N.C. Not internally connected. Do not make connections to these pins.

MAX6659

NAME FUNCTION

Supply Voltage Input, +3V to +5.5V. Bypass to GND with a 0.1µF capacitor. A 200Ω

CC

series resistor is recommended but not required for additional noise filtering. See
Typical Operating Circuit.

Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode
Channel. DO NOT LEAVE DXP UNCONNECTED; connect DXP to DXN if no remote
diode is used. Place a 2200pF capacitor between DXP and DXN for noise filtering.

Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally
biased to one diode drop above ground.

Overtemperature Active-Low Output, Open-Drain. Output is logic low only when
temperature is above the software programmed threshold.

SMBus Alert (Interrupt) Active-Low Output, Open-Drain. Asserts when temperature
exceeds user-set limits (high or low temperature). Stays asserted until acknowledged
by either reading the Status register or by successfully responding to an Alert

ALERT

Response address. See

SMBus Address-Select Pin. The MAX6659 is set to one of three available addresses
(connect to V

Overtemperature Active-Low Output, Open-Drain. Output is logic low only when
temperature is above the software programmed threshold.

Hardware Standby Input. Temperature and comparison threshold data are retained in
standby mode. If STBY is low, the IC is put into standby mode.

, GND, or leave open). See Slave Addresses section.

CC

Interrupts.

MAX6657/MAX6658/MAX6659

Detailed Description

The MAX6657/MAX6658/MAX6659 are temperature
sensors designed to work in conjunction with a micro­processor or other intelligence in thermostatic,
process-control, or monitoring applications. Com­munication with the MAX6657/MAX6658/MAX6659
occurs through the SMBus serial interface and dedicat­ed alert pins. Two independent overtemperature alarms
(OVERT1 and OVERT2) are asserted if their software
programmed temperature thresholds are exceeded.
OVERT1 and OVERT2 can be connected to fans, a sys­tem shutdown, or other thermal management circuitry.

The MAX6657/MAX6658/MAX6659 convert tempera­tures to digital data either at a programmed rate or a
single conversion. Conversions have a 0.125°C resolu­tion (extended resolution) or 1°C resolution (legacy res­olution). Extended resolution represents temperature as

10 bits + sign bit and is available for autonomous con­versions that are 4Hz and slower and single-shot con­versions. Legacy resolution represents temperature as
7 bits + sign bit and allows for faster autonomous con­version rates of 8Hz and 16Hz.

ADC and Multiplexer

The averaging ADC integrates over a 60ms period
(each channel, typically, in the 7-bit + sign legacy
mode). Using an averaging ADC attains excellent noise
rejection.

The multiplexer automatically steers bias currents
through the remote and local diodes. The ADC and
associated circuitry measure each diode’s forward volt­age and compute the temperature based on this volt­age. If the remote channel is not used, connect DXP to
DXN. Do not leave DXP and DXN unconnected. When a
conversion is initiated, both channels are converted

6 _______________________________________________________________________________________

Functional Diagram

±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms

V

CC

MAX6657
MAX6658
MAX6659

2

DXP

DXN

ALERT

Q

OVERT1

Q

(OVERT2)

Q

MUX

REMOTE

LOCAL

DIODE
FAULT

S

R

S

R

S

R

MAX6659 ONLY

ADC

REGISTER BANK

COMMAND BYTE

REMOTE TEMPERATURE

LOCAL TEMPERATURE

ALERT THRESHOLD

ALERT RESPONSE

ADDRESS

OVERT1 THRESHOLD

(OVERT2 THRESHOLD)

8

8

CONTROL

LOGIC

SMBus

READ

WRITE

7

ADDRESS
DECODER

( ) ARE FOR MAX6659 ONLY

(STBY)

SMBDATA

SMBCLK

(ADD)

whether they are used or not. The DXN input is biased
at one VBEabove ground by an internal diode to set up
the ADC inputs for a differential measurement.
Resistance in series with the remote diode causes
about +1/2°C error per ohm.

A/D Conversion Sequence

A conversion sequence consists of a local temperature
measurement and a remote temperature measurement.
Each time a conversion begins, whether initiated auto­matically in the free-running autoconvert mode
(RUN/STOP = 0) or by writing a “one-shot” command,
both channels are converted, and the results of both
measurements are available after the end of conver­sion. A BUSY status bit in the Status register shows that
the device is actually performing a new conversion. The
results of the previous conversion sequence are still
available when the ADC is busy.

Remote-Diode Selection

The MAX6657/MAX6658/MAX6659 can directly mea­sure the die temperature of CPUs and other ICs that
have on-board temperature-sensing diodes (see

Typical Operating Circuit

) or they can measure the tem­perature of a discrete diode-connected transistor. The
type of remote diode used is set by bit 5 of the
Configuration Byte. If bit 5 is set to zero, the remote
sensor is a diode-connected transistor, and if bit 5 is set
to 1, the remote sensor is a substrate or common collec­tor PNP transistor. For best accuracy, the discrete tran­sistor should be a small-signal device with its collector
and base connected together. Accuracy has been
experimentally verified for all the devices listed in Table 1.

The transistor must be a small-signal type with a rela­tively high forward voltage; otherwise, the A/D input
voltage range can be violated. The forward voltage at
the highest expected temperature must be greater than

0.25V at 10µA, and at the lowest expected tempera­ture, forward voltage must be less than 0.95V at 100µA.
Large power transistors must not be used. Also, ensure

that the base resistance is less than 100Ω. Tight speci­fications for forward current gain (50 < β < 150, for
example) indicate that the manufacturer has good
process controls and that the devices have consistent
V

BE

characteristics.

Thermal Mass and Self-Heating

When sensing local temperature, these devices are
intended to measure the temperature of the PC board
to which they are soldered. The leads provide a good
thermal path between the PC board traces and the die.
Thermal conductivity between the die and the ambient
air is poor by comparison, making air temperature mea­surements impractical. Because the thermal mass of
the PC board is far greater than that of the MAX6657/
MAX6658/MAX6659, the devices follow temperature
changes on the PC board with little or no perceivable
delay.

When measuring the temperature of a CPU or other IC
with an on-chip sense junction, thermal mass has virtu­ally no effect; the measured temperature of the junction
tracks the actual temperature within a conversion cycle.
When measuring temperature with discrete remote sen­sors, smaller packages (i.e., a SOT23) yield the best
thermal response times. Take care to account for ther­mal gradients between the heat source and the sensor,
and ensure that stray air currents across the sensor
package do not interfere with measurement accuracy.

Self-heating does not significantly affect measurement
accuracy. Remote-sensor self-heating due to the diode
current source is negligible. For the local diode, the
worst-case error occurs when autoconverting at the
fastest rate and simultaneously sinking maximum cur­rent at the ALERT output. For example, with VCC=
+5.0V, a 16Hz conversion rate and ALERT sinking
1mA, the typical power dissipation is:

VCCx 450µA + 0.4V x 1mA = 2.65mW

θ

J-A

for the 8-pin SO package is about +170°C/W, so
assuming no copper PC board heat sinking, the result­ing temperature rise is:

∆T = 2.65mW x +170°C/W = +0.45°C

Even under these engineered circumstances, it is diffi­cult to introduce significant self-heating errors.

ADC Noise Filtering

The integrating ADC used has good noise rejection for
low-frequency signals such as 60Hz/120Hz power-sup­ply hum. In noisy environments, high-frequency noise
reduction is needed for high-accuracy remote mea-

MAX6657/MAX6658/MAX6659

_______________________________________________________________________________________ 7

Note: Transistors must be diode connected (base shorted to
collector).

Table 1. Remote-Sensor Transistor

±1°C, SMBus-Compatible Remote/Local Temperature

Sensors with Overtemperature Alarms

MANUFACTURER MODEL NUMBER

Central Semiconductor (USA) CMPT3904
Fairchild Semiconductor (USA) 2N3904, 2N3906
On Semiconductor (USA) 2N3904, 2N3906
Rohm Semiconductor (USA) SST3904
Samsung (Korea) KST3904-TF
Siemens (Germany) SMBT3904
Zetex (England) FMMT3904CT-ND

MAX6657/MAX6658/MAX6659

surements. The noise can be reduced with careful PC
board layout and proper external noise filtering.

High-frequency EMI is best filtered at DXP and DXN
with an external 2200pF capacitor. Larger capacitor
values can be used for added filtering, but do not
exceed 3300pF because it can introduce errors due to
the rise time of the switched current source.

PC Board Layout

Follow these guidelines to reduce the measurement
error of the temperature sensors:

1) Place the MAX6657/MAX6658/MAX6659 as close
as is practical to the remote diode. In noisy environ­ments, such as a computer motherboard, this dis­tance can be 4in to 8in (typ). This length can be
increased if the worst noise sources are avoided.
Noise sources include CRTs, clock generators,
memory buses, and ISA/PCI buses.

2) Do not route the DXP-DXN lines next to the deflec­tion coils of a CRT. Also, do not route the traces
across fast digital signals, which can easily intro­duce +30°C error, even with good filtering.

3) Route the DXP and DXN traces in parallel and in
close proximity to each other, away from any higher
voltage traces, such as +12VDC. Leakage currents
from PC board contamination must be dealt with
carefully since a 20MΩ leakage path from DXP to
ground causes about +1°C error. If high-voltage
traces are unavoidable, connect guard traces to GND
on either side of the DXP-DXN traces (Figure 1).

4) Route through as few vias and crossunders as pos­sible to minimize copper/solder thermocouple
effects.

5) When introducing a thermocouple, make sure that
both the DXP and the DXN paths have matching
thermocouples. A copper-solder thermocouple
exhibits 3µV/°C, and it takes about 200µV of voltage
error at DXP-DXN to cause a +1°C measurement
error. Adding a few thermocouples causes a negli­gible error.

6) Use wide traces. Narrow traces are more inductive
and tend to pick up radiated noise. The 10mil widths
and spacings that are recommended in Figure 1 are
not absolutely necessary, as they offer only a minor
improvement in leakage and noise over narrow
traces. Use wider traces when practical.

7) Add a 200Ω resistor in series with VCCfor best
noise filtering (see

Typical Operating Circuit

).

Twisted-Pair and Shielded Cables

Use a twisted-pair cable to connect the remote sensor
for remote-sensor distances longer than 8in or in very
noisy environments. Twisted-pair cable lengths can be
between 6ft and 12ft before noise introduces excessive
errors. For longer distances, the best solution is a
shielded twisted pair like that used for audio micro­phones. For example, Belden #8451 works well for dis­tances up to 100ft in a noisy environment. At the
device, connect the twisted pair to DXP and DXN and
the shield to GND. Leave the shield unconnected at the
remote sensor.

For very long cable runs, the cable’s parasitic capaci­tance often provides noise filtering, so the 2200pF
capacitor can often be removed or reduced in value.
Cable resistance also affects remote-sensor accuracy.
For every 1Ω of series resistance, the error is approxi­mately +1/2°C.

Low-Power Standby Mode

Standby mode reduces the supply current to less than
10µA by disabling the ADC. Enter hardware standby
(MAX6659 only) by forcing the STBY pin low, or enter
software standby by setting the RUN/STOP bit to 1 in
the Configuration Byte register. Hardware and software
standbys are very similar—all data is retained in memo­ry, and the SMB interface is alive and listening for
SMBus commands. The only difference is that in soft­ware standby mode, the one-shot command initiates a
conversion. With hardware standby, the one-shot com­mand is ignored. Activity on the SMBus causes the
device to draw extra supply current.

Driving the STBY pin low overrides any software con­version command. If a hardware or software standby
command is received while a conversion is in progress,
the conversion cycle is interrupted, and the tempera-

8 _______________________________________________________________________________________

Figure 1. Recommended DXP-DXN PC Traces

±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms

GND

10MILS

10MILS

10MILS

DXP

MINIMUM

DXN

10MILS

GND

ture registers are not updated. The previous data is not
changed and remains available.

SMBus Digital Interface

From a software perspective, each of the MAX6657/
MAX6658/MAX6659 appears as a series of 8-bit regis­ters that contain temperature data, alarm threshold
values, and control bits. A standard SMBus-compatible
2-wire serial interface is used to read Temperature Data
and Write Control bits and alarm threshold data. The
device responds to the same SMBus slave address for
access to all functions.

The MAX6657/MAX6658/MAX6659 employ four stan­dard SMBus protocols: Write Byte, Read Byte, Send
Byte, and Receive Byte (Figures 2, 3, and 4). The short­er Receive Byte protocol allows quicker transfers, pro­vided that the correct data register was previously
selected by a Read Byte instruction. Use caution with
the shorter protocols in multimaster systems, since a
second master could overwrite the command byte with­out informing the first master.

When the conversion rate is greater than 4Hz, temperature
data can be read from the Read Internal Temperature
(00h) and Read External Temperature (01h) registers.

The temperature data format is 7 bits + sign in two's­complement form for each channel, with the LSB repre­senting 1°C (Table 2). The MSB is transmitted first.

When the conversion rate is 4Hz or less, the first 8 bits
of temperature data can be read from the Read Internal
Temperature (00h) and Read External Temperature
(01h) registers, the same as for faster conversion rates.
An additional 3 bits can be read from the Read External
Extended Temperature (10h) and Read Internal
Extended Temperature (11h) registers, which extends
the data to 10 bits + sign and the resolution to
+0.125°C per LSB (Table 3).

When a conversion is complete, the Main register and
the Extended register are updated almost simultane­ously. Ensure that no conversions are completed
between reading the Main and Extended registers so
that when data that is read, both registers contain the
result of the same conversion.

To ensure valid extended data, read extended resolu­tion temperature data using one of the following
approaches:

1) Put the MAX6657/MAX6658/MAX6659 into standby

mode by setting bit 6 of the Configuration register to

MAX6657/MAX6658/MAX6659

______________________________________________________________________________________ 9

Figure 2. SMBus Protocols

ACK

7 bits

ADDRESS ACKWR

8 bits

DATA ACK

1

P

8 bits

S COMMAND

Write Byte Format

Read Byte Format

Send Byte Format Receive Byte Format

Slave Address: equiva­lent to chip-select line of
a 3-wire interface

Command Byte: selects which
register you are writing to

Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)

ACK

7 bits

ADDRESS ACKWR S ACK

8 bits

DATA

7 bits

ADDRESS RD

8 bits

/// PCOMMAND

Slave Address: equiva­lent to chip-select line

Command Byte: selects
which register you are
reading from

Slave Address: repeated
due to change in data­flow direction

Data Byte: reads from
the register set by the
command byte

ACK

7 bits

ADDRESS WR

8 bits

COMMAND ACK P ACK

7 bits

ADDRESS RD

8 bits

DATA /// PS

Command Byte: sends com­mand with no data, usually
used for one-shot command

Data Byte: reads data from
the register commanded
by the last Read Byte or
Write Byte transmission;
also used for SMBus Alert
Response return address

S = Start condition Shaded = Slave transmission
P = Stop condition /// = Not acknowledged

±1°C, SMBus-Compatible Remote/Local Temperature

Sensors with Overtemperature Alarms

MAX6657/MAX6658/MAX6659

1. Initiate a one-shot conversion using Command
Byte 0Fh. When this conversion is complete, read
the contents of the Temperature Data registers.

2) If the MAX6657/MAX6658/MAX6659 are in run mode,
read the Status register. If a conversion is in
progress, the BUSY bit is set to 1. Wait for the con­version to complete as indicated by the BUSY bit
being set to 0, then read the Temperature Data reg­isters. Note that the power-on reset sets the conver­sion rate to 16Hz, so no extended data is valid
without reducing the conversion rate to 4Hz or less.

Diode Fault Alarm

There is a continuity fault detector at DXP that detects
an open circuit between DXP and DXN, or a DXP short
to VCC, GND, or DXN. If an open or short circuit exists,
the external temperature register is loaded with 1000

0000. Additionally, if the fault is an open circuit, bit 2
(OPEN) of the status byte is set to 1 and the ALERT con­dition is activated at the end of the conversion.
Immediately after POR, the Status register indicates that
no fault is present until the end of the first conversion.

10 ______________________________________________________________________________________

Figure 4. SMBus Read Timing Diagram

Figure 3. SMBus Write Timing Diagram

±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms

AB CDEFG HIJ

t

LOWtHIGH

SMBCLK

SMBDATA

t

t

HD:STA

SU:STA

A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW

t

SU:DAT

F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = MASTER PULLS DATA LINE LOW

t

HD:DAT

AB CDEFG HIJ

t

LOWtHIGH

SMBCLK

SMBDATA

t

SU:STA

t

HD:STA

t

SU:DAT

t

HD:DAT

K

t

SU:STO

J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION

K

t

SU:STO

M

L

t

BUF

M

L

t

BUF

A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW

F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = MASTER PULLS DATA LINE LOW

J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION

Alarm Threshold Registers

Four registers store ALERT threshold values—one high­temperature (T

HIGH

) and one low-temperature (T

LOW

)
register each for the local and remote channels. If
either measured temperature equals or exceeds the
corresponding ALERT threshold value, the ALERT out­put is asserted.

The POR state of both ALERT T

HIGH

registers is 0100

0110 or +70°C and the POR state of T

LOW

registers is

1100 1001 or -55°C.

Four additional registers store remote and local alarm
threshold data corresponding to the OVERT1 and
OVERT2 (MAX6659 only) outputs. The values stored in
these registers are high-temperature thresholds. If any
one of the measured temperatures equals or exceeds
the corresponding alarm threshold value, an OVERT
output is asserted. The POR state of the OVERT thresh­old is 0101 0101 or +85°C.

Alert

Interrupts

An ALERT interrupt occurs when the internal or external
temperature reading exceeds a high or low tempera­ture limit (user programmed) or when the remote diode
is disconnected (for continuity fault detection). The
ALERT interrupt output signal is latched and can be
cleared only by either reading the Status register or by
successfully responding to an Alert Response address.
In both cases, the alert is cleared even if the fault con­dition still exists, but is reasserted at the end of the next
conversion. The interrupt does not halt automatic con­versions. The interrupt output pin is open-drain so that
multiple devices can share a common interrupt line.
The interrupt rate never exceeds the conversion rate.

Alert Response Address

The SMBus Alert Response interrupt pointer provides
quick fault identification for simple slave devices that
lack the complex, expensive logic needed to be a bus
master. Upon receiving an ALERT interrupt signal, the
host master can broadcast a Receive Byte transmission
to the Alert Response slave address (0001100). Then,
any slave device that generated an interrupt attempts
to identify itself by putting its own address on the bus
(Table 8).

The Alert Response can activate several different slave
devices simultaneously, similar to the I2C General Call.
If more than one slave attempts to respond, bus arbitra­tion rules apply, and the device with the lower address
code wins. The losing device does not generate an
acknowledge and continues to hold the ALERT line low
until cleared. (The conditions for clearing an alert vary,
depending on the type of slave device.) Successful
completion of the Alert Response protocol clears the
interrupt latch, provided the condition that caused the
alert no longer exists. If the condition still exists, the
device reasserts the ALERT interrupt at the end of the
next conversion.

OVERT

Overtemperature

Alarm/Warning Outputs

OVERT1 and OVERT2 (MAX6659 only) are asserted
when the temperature rises to a value programmed in
the appropriate threshold register. They are deasserted
when the temperature drops below this threshold minus
the hysteresis. An OVERT output can be used to acti­vate a cooling fan, send a warning, or trigger a system
shutdown to prevent component damage. The HYST
byte sets the amount of hysteresis for both OVERT out­puts. The data format for the HYST byte is the same for
the other temperature registers (Table 2).

MAX6657/MAX6658/MAX6659

______________________________________________________________________________________ 11

Table 3. Extended Resolution Register

Note: Extended resolution applies only for conversion rates of
4Hz and slower.

Table 2. Data Format (Two's Complement)

±1°C, SMBus-Compatible Remote/Local Temperature

Sensors with Overtemperature Alarms

DIGITAL OUTPUT

TEMP (°C)

130.00 0 111 1111 0 111 1111

127.00 0 111 1111 0 111 1111

126.00 0 111 1111 0 111 1111

25 0 001 1001 0 001 1001

0.00 0 000 0000 0 000 0000

-1 1 000 0000 1 111 1111

-25 1 000 0000 1 110 0111

-55 1 000 0000 1 100 1001

Diode Fault

(Short or Open)

MAX6657

1 000 0000 1 000 0000

MAX6658
MAX6659

FRACTIONAL

TEMPERATURE

0.000 000X XXXX

0.125 001X XXXX

0.250 010X XXXX

0.375 011X XXXX

0.500 100X XXXX

0.625 101X XXXX

0.750 110X XXXX

0.875 111X XXXX

CONTENTS OF

EXTENDED REGISTER

MAX6657/MAX6658/MAX6659

For example, OVERT1 has a threshold set to +50°C
and is connected to a fan. OVERT2 has a threshold of
+75°C and is connected to a system shutdown. If the
system reaches +50°C, the fan turns on, trying to cool
the system. If the system continues to heat up to the
critical temperature of +75°C, OVERT2 causes the sys­tem to shut down.

Command Byte Functions

The 8-bit Command Byte register (Table 4) is the master
index that points to the various other registers within the
MAX6657/MAX6658/MAX6659. This register’s POR state
is 0000 0000, so a Receive Byte transmission (a protocol
that lacks the command byte) occurring immediately
after POR returns the current local temperature data.

One-Shot

The one-shot command immediately forces a new con­version cycle to begin. If the one-shot command is
received when the MAX6657/MAX6658/MAX6659 are in

software standby mode (RUN/STOP bit = 1), a new
conversion is begun, after which the device returns to
standby mode. If a conversion is in progress when a
one-shot command is received, the command is
ignored. If a one-shot command is received in autocon­vert mode (RUN/STOP bit = 0) between conversions, a
new conversion begins, the conversion rate timer is
reset, and the next automatic conversion takes place
after a full delay elapses.

Configuration Byte Functions

The Configuration Byte register (Table 5) is a Read-Write
register with several functions. Bit 7 is used to mask (dis­able) interrupts. Bit 6 puts the device into software stand­by mode (STOP) or autonomous (RUN) mode. Bit 5
selects the type of external junction (set to 1 for a sub­strate PNP on an IC or set to 0 for a discrete diode-con­nected transistor) for optimized measurements. Bits 0 to
4 are reserved and return a zero when read.

12 ______________________________________________________________________________________

Table 4. Command Byte Register Assignments

±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms

REGISTER ADDRESS POR STATE FUNCTION

RLTS 00h 0000 0000 Read Internal Temperature

RRTE 01h 0000 0000 Read External Temperature

RSL 02h 1000 0000 Read Status Register

RCL 03h 0010 0000 Read Configuration Byte

RCRA 04h 0000 1000 Read Conversion Rate Byte

RLHN 05h 0100 0110 Read Internal High Limit

RLLI 06h 1100 1001 Read Internal Low Limit

RRHI 07h 0100 0110 Read External High Limit

RRLS 08h 1100 1001 Read External Low Limit

WCA 09h 0010 0000 Write Configuration Byte

WCRW 0Ah 0000 1000 Write Conversion Rate Byte

WLHO 0Bh 0100 0110 Write Internal High Limit

WLLM 0Ch 1100 1001 Write Internal Low Limit

WRHA 0Dh 0100 0110 Write External High Limit

WRLN 0Eh 1100 1001 Write External Low Limit

OSHT 0Fh N/A One Shot

REET 10h 0000 0000 Read External Extended Temperature

RIET 11h 0000 0000 Read Internal Extended Temperature

RWO2E 16h 0101 0101 Read/Write External OVERT2 Limit (MAX6659 only)

RW02I 17h 0101 0101 Read/Write Internal OVERT2 Limit (MAX6659 only)
RWOE 19h 0101 0101 Read/Write External OVERT1 Limit

RWOI 20h 0101 0101 Read/Write Internal OVERT1 Limit

HYST 21h 0000 1010 Overtemperature Hysteresis

— FEh 4Dh Read Manufacture ID

MAX6657/MAX6658/MAX6659

______________________________________________________________________________________ 13

Status Byte Functions

The status byte (Table 6) indicates which (if any) tem­perature thresholds have been exceeded. This byte also
indicates whether the ADC is converting and if there is
an open-circuit fault detected with the external sense
junction. After POR, the normal state of the MSB is 1 and
all the other flag bits are 0, assuming no alert or
overtemperature conditions are present. Bits 2 through
6 of the Status register are cleared by any successful
read of the Status register, unless the fault persists. The

ALERT output follows the status flag bit. Both are
cleared when successfully read, but if the condition still
exists, they reassert at the end of the next conversion.

The bits indicating OVERT1 (bits 0 and 1) are cleared
only when the condition no longer exists. Reading the
status byte does not clear the OVERT1 outputs or fault
bits. One way to eliminate the fault condition is for the
measured temperature to drop below the temperature
threshold minus the hysteresis value. Another way to
eliminate the fault condition is by writing new values for
the OVERT1 threshold or hysteresis so that a fault con­dition is no longer present. Note that the status byte
does not provide status of OVERT2.

The MAX6657/MAX6658/MAX6659 incorporate collision
avoidance so that completely asynchronous operation
is allowed between SMBus operations and temperature
conversions.

When autoconverting, if the T

HIGH

and T

LOW

limits are
close together, it’s possible for both high-temp and low­temp status bits to be set, depending on the amount of
time between status read operations. In these circum­stances, it is best not to rely on the status bits to indi­cate reversals in long-term temperature changes.
Instead, use a current temperature reading to establish
the trend direction.

Conversion Rate Byte

The Conversion Rate register (Table 7) programs the
time interval between conversions in free-running
autonomous mode (RUN/STOP = 0). This variable rate

Table 5. Configuration-Byte Bit
Assignments

Table 6. Status Register Bit Assignments

±1°C, SMBus-Compatible Remote/Local Temperature

Sensors with Overtemperature Alarms

BIT NAME

7

(MSB)

4 to 0 RFU 0 Reserved

MASK1 0 Masks ALERT interrupts if a 1.

6 RUN/STOP 0

5 SPNP 1

POR

STATE

FUNCTION

Standby mode control bit; if a
1, standby mode is initiated.

Set to 1 when the remote
sensor is a substrate or
common collector PNP. Set to 0
when the remote sensor is a
diode-connected discrete
transistor.

BIT NAME POR STATE FUNCTION

7 (MSB) BUSY 1 A/D is busy converting when high.

6 LHIGH 0

5 LLOW 0

4 RHIGH 0

3 RLOW 0

2 OPEN 0

1 EOT1 0

0 IOT1 0

Internal high-temperature alarm has tripped when high; cleared by POR or readout of
the Status register if the fault condition no longer exists.

Internal low-temperature alarm has tripped when high; cleared by POR or readout of
the Status register if the fault condition no longer exists.

External high-temperature alarm has tripped when high; cleared by POR or readout of
the Status register if the fault condition no longer exists.

External low-temperature alarm has tripped when high; cleared by POR or readout of
the Status register if the fault condition no longer exists.

A high indicates an external diode open; cleared by POR or readout of the Status
register if the fault condition no longer exists.

A high indicates the external junction temperature exceeds the external OVERT1
threshold.

A high indicates the internal junction temperature exceeds the internal OVERT1
threshold.

MAX6657/MAX6658/MAX6659

control can be used to reduce the supply current in
portable-equipment applications. The conversion rate
byte’s POR state is 08h (16Hz). The MAX6657/
MAX6658/MAX6659 use only the 4 least-significant bits
(LSBs) of this register. The 4 most-significant bits
(MSBs) are “don’t care” and should be set to zero when
possible. The conversion rate tolerance is ±25% at any
rate setting.

Valid A/D conversion results for both channels are
available one total conversion time (125ms nominal,
156ms maximum) after initiating a conversion, whether
conversion is initiated through the RUN/STOP bit, hard­ware STBY pin, one-shot command, or initial power-up.

Slave Addresses

The MAX6657/MAX6658 have a fixed address of

1001100. The MAX6659 can be programmed to have
one of three different addresses, allowing up to three
devices to reside on the same bus without address
conflicts. Table 8 lists address information.

The address pin state is checked at POR only, and the
address data stays latched to reduce quiescent supply
current due to the bias current needed for high-Z state
detection.

The MAX6657/MAX6658/MAX6659 also respond to the
SMBus Alert Response slave address (see

Alert

Response Address

section).

POR and UVLO

The MAX6657/MAX6658/MAX6659 have a volatile
memory. To prevent unreliable power-supply conditions

from corrupting the data in memory and causing erratic
behavior, a POR voltage detector monitors V

CC

and

clears the memory if V

CC

falls below 1.7V (typ, see

Electrical Characteristics

). When power is first applied
and VCCrises above 2.0V (typ), the logic blocks begin
operating, although reads and writes at V

CC

levels
below 3.0V are not recommended. A second VCCcom­parator and the ADC undervoltage lockout (UVLO)
comparator prevent the ADC from converting until there
is sufficient headroom (VCC= +2.8V typ).

Power-Up Defaults

Power-up defaults include:

• ADC begins autoconverting at a 16Hz rate (legacy

resolution).

• THIGH and TLOW registers are set to default limits,

respectively.

• Interrupt latch is cleared.

• Address-select pin is sampled (MAX6659 only).

• Command register is set to 00h to facilitate quick

internal Receive Byte queries.

• Hysteresis is set to 10°C.

• Transistor type is set to a substrate or common col-

lector PNP.

14 ______________________________________________________________________________________

Table 8. Slave Address Decoding for
MAX6659

Note: Extended resolution applies only for conversion rates of
4Hz or slower.

Table 7. Conversion-Rate
Control Byte

Table 9. Read Format for Alert Response
Address (000 1100)

±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms

DATA CONVERSION RATE (Hz)

00h 0.0625

01h 0.125

02h 0.25

03h 0.5

04h 1

05h 2

06h 4

07h 8

08h 16

09h 16

0Ah-FFh Reserved

ADD CONNECTION ADDRESS

BIT NAME FUNCTION

7 (MSB) ADD7

6 ADD6

5 ADD5

4 ADD4

3 ADD3

2 ADD2

1 ADD1

0 (LSB) 1 Logic 1

GND 1001100

V

CC

Unconnected 1001101

1001110

Provide the current
MAX6659 slave address
that was latched at POR
(Table 8)

MAX6657/MAX6658/MAX6659

______________________________________________________________________________________ 15

Chip Information

PROCESS: BiCMOS

V

CC

SMBDATA

SMBCLK

DATA

CLOCK

INTERRUPTED TO µP

TO FAN DRIVER

() ARE MAX6659 ONLY

TO SYSTEM SHUTDOWN

(ADD) GND

µP

3.3V

200Ω

2200pF

10kΩ
EACH

0.1µF

DXP

DXN

ALERT

OVERT1

(OVERT2)

(STBY)

MAX6657
MAX6658
MAX6659



Typical Operating Circuit

±1°C, SMBus-Compatible Remote/Local Temperature

Sensors with Overtemperature Alarms

Package Information

For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages

. Note that a “+”, “#”, or “-” in
the package code indicates RoHS status only. Package draw­ings may show a different suffix character, but the drawing per­tains to the package regardless of RoHS status.

PACKAGE

TYPE

PACKAGE

CODE

OUTLINE NO.

LAND

PATTERN NO.

8 SO S8-5

21-0041

90-0096

16 QSOP E16-5

21-0055

90-0167

Ordering Information (continued)

Note: All devices are specified over the -55°C to +125°C oper­ating temperature range.

+

Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

PART

MAX6658MSA -55°C to +125°C 8 SO

MAX6658MSA+ -55°C to +125°C 8 SO

MAX6658MSA-T -55°C to +125°C 8 SO

MAX6658MSA+T -55°C to +125°C 8 SO

MAX6659MEE -55°C to +125°C 16 QSOP

MAX6659MEE+ -55°C to +125°C 16 QSOP

MAX6659MEE-T -55°C to +125°C 16 QSOP

MAX6659MEE+T -55°C to +125°C 16 QSOP

MEASURED TEMP

RANGE

PIN-PACKAGE

MAX6657/MAX6658/MAX6659

1°C Remote/Local Temperature Sensors with SMBus
Serial Interface and Overtemperature Alarms

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.

16

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

Revision History

REVISION

NUMBER

5 10/10

REVISION

DATE

DESCRIPTION

Updated the Ordering Information table to include lead(Pb)-free parts, added the
soldering temperature to the Absolute Maximum Ratings section, replaced the
package outline drawings with the Package Information table

PAGES

CHANGED

1, 2, 15