MAXIM MAX6698 Technical data

General Description

The MAX6698 precision multichannel temperature sen­sor monitors its own temperature, the temperatures of
three external diode-connected transistors, and the
temperatures of three thermistors. All temperature
channels have programmable alert thresholds.
Channels 1, 4, 5, and 6 also have programmable over­temperature thresholds. When the measured tempera­ture of a channel exceeds the respective threshold, a
status bit is set in one of the status registers. Two open­drain outputs, OVERT and ALERT, assert correspond­ing to these bits in the status register.

The 2-wire serial interface supports the standard system
management bus (SMBus™) protocols: write byte, read
byte, send byte, and receive byte for reading the tem­perature data and programming the alarm thresholds.

The MAX6698 is specified for an operating temperature
range of -40°C to +125°C and is available in 16-pin
QSOP and 16-pin TSSOP packages.

Applications

Desktop Computers Workstations

Notebook Computers Servers

Features

♦ Three Thermal-Diode Inputs and Three Thermistor

Inputs

♦ Local Temperature Sensor

♦ 1°C Remote Temperature Accuracy (+60°C to

+100°C)

♦ Temperature Monitoring Begins at POR for Fail-

Safe System Protection

♦ ALERT and OVERT Outputs for Interrupts,

Throttling, and Shutdown

♦ Small 16-Pin QSOP and 16-Pin TSSOP Packages

♦ 2-Wire SMBus Interface

MAX6698

7-Channel Precision Remote-Diode, Thermistor,

and Local Temperature Monitor

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

16

+3.3V

15

14

13

12

11

10

9

1

2

3

4

5

6

R

EX3

R

THER3

7

8

GND

SMBCLK

SMBDATA

DXN2

DXP2

DXN1

DXP1

V

CC

THER1

THER2VREF

THER3

DXN3

DXP3

MAX6698

ALERT

OVERT

R

EX2

R

THER2

R

EX1

R

THER1

Typical Application Circuit

19-3476; Rev 3; 8/07

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.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE

PIN­PACKAGE

PKG
CODE

MAX6698EE_ _

-40°C to +125°C

16 QSOP

E16-1

MAX6698UE_ _

-40°C to +125°C

16 TSSOP

U16-1

SMBus is a trademark of Intel Corp.

Pin Configuration appears at end of data sheet.

*See the Slave Address section.

MAX6698

7-Channel Precision Remote-Diode, Thermistor,
and Local Temperature Monitor

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.

VCC, SCL, SDA, ALERT, OVERT to GND ................-0.3V to +6V

DXP_ to GND..............................................-0.3V to (V

CC

+ 0.3V)

DXN_ to GND ........................................................-0.3V to +0.8V

THER_ to GND..........................................................-0.3V to +6V

VREF to GND............................................................-0.3V to +6V

SDA, ALERT, OVERT Current .............................-1mA to +50mA

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

Continuous Power Dissipation (T

A

= +70°C)
16-Pin QSOP

(derate 8.3mW/°C above +70°C) ......................666.7mW(E16-1)

16-Pin TSSOP

(derate 9.4mW/°C above +70°C)....................754.7mW(U16-1)

ESD Protection (all pins, Human Body Model) ................±2000V

Operating Temperature Range .........................-40°C to +125°C

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

Storage Temperature Range .............................-60°C to +150°C

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

ELECTRICAL CHARACTERISTICS

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

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Supply Voltage V

CC

3.0 5.5 V

Standby Supply Current I

SS

SMBus static 30 µA

Operating Current I

CC

During conversion

µA

Channel 1 only 11

Temperature Resolution

Other diode channels 8

Bits

TA = T

RJ

= 0°C to +125°C

Remote Temperature Accuracy VCC = 3.3V

DXN_ grounded,
T

RJ

= TA = 0°C to +85°C

o

C

TA = +60°C to +100°C

Local Temperature Accuracy VCC = 3.3V

T

A

= 0°C to +125°C

o

C

Supply Sensitivity of Temperature
Accuracy

o

C/V

Resistance cancellation on 95

Remote Channel 1 Conversion
Time

t

CONV1

Resistance cancellation off

ms

Remote Channels 2 Through 6
Conversion Time

t

CONV_

95

ms

High level 80

Remote-Diode Source Current I

RJ

Low level 8 10 12

µA

Undervoltage-Lockout Threshold

UVLO Falling edge of V

CC

disables ADC 2.3

V

Undervoltage-Lockout Hysteresis

90 mV

Power-On Reset (POR) Threshold

VCC falling edge 1.2 2.0 2.5 V

POR Threshold Hysteresis 90 mV

THERMISTOR CONVERSION

Voltage-Measurement Accuracy

-1 +1

%Full

scale

Conversion Time 31 ms

Thermistor Reference Voltage V

REF

1V

500 1000

TA = T

= +60°C to +100°C -1.0 +1.0

RJ

-3.0 +3.0

-2.5 +2.5

-3.5 +3.5

±0.2

125 156

190 250 312

125 156

100 120

2.80 2.95

±2.5

MAX6698

7-Channel Precision Remote-Diode, Thermistor,

and Local Temperature Monitor

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

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

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Reference-Load Regulation 0mA < I

REF

< 2mA 0.4 %

Reference-Supply Rejection 0.5 %/V

ALERT, OVERT

I

SINK

= 1mA 0.3

Output Low Voltage V

OL

I

SINK

= 6mA 0.5

V

Output Leakage Current 1µA

SMBus INTERFACE (SCL, SDA)

Logic-Input Low Voltage V

IL

0.8 V

VCC = 3.0V 2.2 V

Logic-Input High Voltage V

IH

VCC = 5.0V 2.4 V

Input Leakage Current -1 +1 µA

Output Low Voltage V

OL

I

SINK

= 6mA 0.3 V

Input Capacitance C

IN

5pF

SMBus-COMPATIBLE TIMING (Figures 3 and 4) (Note 2)

Serial Clock Frequency f

SCL

(Note 3)

kHz

f

SCL

= 100kHz 4.7

Bus Free Time Between STOP
and START Condition

t

BUF

f

SCL

= 400kHz 1.6

µs

f

SCL

= 100kHz 4.7

START Condition Setup Time

f

SCL

= 400kHz 0.6

µs

0.6

Repeat START Condition Setup
Time

t

SU:STA

0.6

µs

START Condition Hold Time t

HD:STA

10% of SDA to 90% of SCL 0.6 µs

4

STOP Condition Setup Time t

SU:STO

0.6

µs

10% to 10%, f

SCL

= 100kHz 1.3

Clock Low Period t

LOW

10% to 10%, f

SCL

= 400kHz 1.3

µs

Clock High Period t

HIGH

90% to 90% 0.6 µs

f

SCL

= 100kHz

Data Hold Time t

HD:DAT

f

SCL

= 400kHz (Note 4)

ns

f

SCL

= 100kHz

Data Setup Time t

SU:DAT

f

SCL

= 400kHz

ns

f

SCL

= 100kHz 1

Receive SCL/SDA Rise Time t

R

f

SCL

= 400kHz 0.3

µs

Receive SCL/SDA Fall Time t

F

ns

Pulse Width of Spike Suppressed

t

SP

050ns

SMBus Timeout

SDA low period for interface reset 25 37 45 ms

Note 1: All parameters are tested at TA= +25°C. Specifications over temperature are guaranteed by design.
Note 2: Timing specifications are guaranteed by design.
Note 3: The serial interface resets when SCL is low for more than t

TIMEOUT

.

Note 4: A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SCL’s falling edge.

t

TIMEOUT

90% of SCL to 90% of SDA, f

90% of SCL to 90% of SDA, f

90% of SCL to 90% of SDA, f

90% of SCL to 90% of SDA, f

= 100kHz

SCL

= 400kHz

SCL

= 100kHz

SCL

= 400kHz

SCL

300

250

100

400

900

300

MAX6698

7-Channel Precision Remote-Diode, Thermistor,
and Local Temperature Monitor

4 _______________________________________________________________________________________

Typical Operating Characteristics

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

STANDBY SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX6698 toc01

SUPPLY VOLTAGE (V)

STANDBY SUPPLY CURRENT (µA)

5.34.84.3

3.8

1

2

3

4

5

6

7

8

9

10

11

12

0

3.3

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX6698 toc02

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

5.34.8

3.8 4.3

325

330

335

340

350

345

355

360

320

3.3

-4

-2

-3

0

-1

2

1

3

05025 75 100 125

REMOTE TEMPERATURE ERROR

vs. REMOTE-DIODE TEMPERATURE

MAX6698 toc03

REMOTE-DIODE TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

-4

-3

-2

-1

0

1

2

3

4

0 25 50 75 100 125

LOCAL TEMPERATURE ERROR

vs. DIE TEMPERATURE

MAX6698 toc04

DIE TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

REMOTE-DIODE TEMPERATURE ERROR

vs. POWER-SUPPLY NOISE FREQUENCY

MAX6698 toc05

FREQUENCY (MHz)

TEMPERATURE ERROR (°C)

-4

-3

-2

-1

0

1

2

3

4

5

-5

0.1 1

100mV

P-P

LOCAL TEMPERATURE ERROR

vs. POWER-SUPPLY NOISE FREQUENCY

MAX6698 toc06

FREQUENCY (MHz)

TEMPERATURE ERROR (°C)

0.10.01

-4

-3

-2

-1

0

1

2

3

4

5

-5

0.001 1

100mV

P-P

REMOTE TEMPERATURE ERROR

vs. COMMON-MODE NOISE FREQUENCY

MAX6698 toc07

FREQUENCY (MHz)

TEMPERATURE ERROR (°C)

10.10.01

-4

-3

-2

-1

0

1

2

3

4

5

-5

0.001 10

100mV

P-P

REMOTE TEMPERATURE ERROR

vs. COMMON-MODE NOISE FREQUENCY

MAX6698 toc08

FREQUENCY (MHz)

TEMPERATURE ERROR (°C)

10.10.01

-4

-3

-2

-1

0

1

2

3

4

5

-5

0.001 10

100mV

P-P

MAX6698

_______________________________________________________________________________________ 5

TEMPERATURE ERROR

vs. DXP-DXN CAPACITANCE

MAX6698 toc09

DXP-DXN CAPACITANCE (nF)

TEMPERATURE ERROR (°C)

10

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0

-5.0
1 100

MAX6698

7-Channel Precision Remote-Diode, Thermistor,

and Local Temperature Monitor

Typical Operating Characteristics (continued)

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

0

10

5

20

15

25

30

05025 75 100 125

ALERT, OVERT SINK CURRENT

vs. TEMPERATURE

MAX6698 toc10

TEMPERATURE (°C)

ALERT SINK CURRENT (mA)

VOL = 0.3V

VOL = 0.1V

THERMISTOR ADC ERROR

vs. POWER-SUPPLY NOISE FREQUENCY

MAX6698 toc11

FREQUENCY (MHz)

TEMPERATURE ERROR (°C)

1010.1

-4

-3

-2

-1

0

1

2

3

4

5

-5

0.01 100

100mV

P-P

Pin Description

PIN NAME FUNCTION

1 DXP1

Combined Current Source and A/D Positive Input for Channel 1 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no
remote diode is used. Place a 2200pF capacitor between DXP1 and DXN1 for noise filtering.

2 DXN1

Cathode Input for Channel 1 Remote Diode. Connect the cathode of the channel 1 remote-diode­connected transistor to DXN1.

3 DXP2

Combined Current Source and A/D Positive Input for Channel 2 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to V

CC

if no

remote diode is used. Place a 2200pF capacitor between DXP2 and DXN2 for noise filtering.

4 DXN2

Cathode Input for Channel 2 Remote Diode. Connect the cathode of the channel 2 remote-diode­connected transistor to DXN2.

5 DXP3

Combined Current Source and A/D Positive Input for Channel 3 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no
remote diode is used. Place a 2200pF capacitor between DXP3 and DXN3 for noise filtering.

6 DXN3

Cathode Input for Channel 3 Remote Diode. Connect the cathode of the channel 1 remote-diode­connected transistor to DXN3.

7 THER3

Thermistor Voltage Sense Input 3. Connect thermistor 3 between THER3 and ground and an external
resistor R

EXT3

between THER3 and VREF.

8 VREF

Thermistor Reference Voltage (1V Nominal). VREF is automatically enabled for a thermistor
conversion, and is disabled for diode measurements.

MAX6698

Detailed Description

The MAX6698 is a precision multichannel temperature
monitor that features one local, three remote thermal
diode temperature-sensing channels, and three ther­mistor voltage-sensing channels. All channels have a
programmable alert threshold for each temperature
channel and a programmable overtemperature thresh­old for channels 1, 4, 5, and 6 (see Figure 1).
Communication with the MAX6698 is achieved through
the SMBus serial interface and a dedicated alert
(ALERT) pin. The alarm outputs, OVERT and ALERT,
assert if the software-programmed temperature thresh­olds are exceeded. ALERT typically serves as an inter­rupt, while OVERT can be connected to a fan, system
shutdown, or other thermal-management circuitry.

Note that thermistor “temperature data” is really the volt­age across the fixed resistor, R

EXT

, in series with the
thermistor. This voltage is directly related to temperature,
but the data is expressed in percentage of the reference
voltage not in °C.

ADC Conversion Sequence

In the default conversion mode, the MAX6698 starts the
conversion sequence by measuring the temperature on
the channel 1 remote diode, followed by the channel 2,
remote diode, channel 3 remote diode, and the local
channel. Then it measures thermistor channel 1, ther­mistor channel 2, and thermistor channel 3. The con-

version result for each active channel is stored in the
corresponding temperature data register.

In some systems, one of the remote thermal diodes may
be monitoring a location that experiences temperature
changes that occur much more rapidly than in the other
channels. If faster temperature changes must be moni­tored in one of the temperature channels, the MAX6698
allows channel 1 to be monitored at a faster rate than the
other channels. In this mode (set by writing a 1 to bit 4 of
the configuration 1 register), measurements of channel 1
alternate with measurements of the other channels. The
sequence becomes remote-diode channel 1, remote­diode channel 2, remote-diode channel 1, remote-diode
channel 3, remote-diode channel 1, etc. Note that the
time required to measure all seven channels is consider­ably greater in this mode than in the default mode.

Low-Power Standby Mode

Standby mode reduces the supply current to less than
15µA by disabling the internal ADC. Enter standby by
setting the STOP bit to 1 in the configuration 1 register.
During standby, data is retained in memory, and the
SMBus interface is active and listening for SMBus com­mands. The timeout is enabled if a start condition is rec­ognized on the SMBus. Activity on the SMBus causes
the supply current to increase. If a standby command is
received while a conversion is in progress, the conver­sion cycle is interrupted, and the temperature registers
are not updated. The previous data is not changed and
remains available.

7-Channel Precision Remote-Diode, Thermistor,
and Local Temperature Monitor

6 _______________________________________________________________________________________

Pin Description (continued)

PIN NAME FUNCTION

9 THER2

Thermistor Voltage Sense Input 2. Connect thermistor 2 between THER2 and ground and an external
resistor R

EXT3

between THER2 and VREF.

10 THER1

Thermistor Voltage Sense Input 1. Connect thermistor 1 between THER1 and ground and an external
resistor R

EXT3

between THER1 and VREF.

11 OVERT

Overtemperature Active-Low, Open-Drain Output. OVERT asserts low when the temperature of
channels 1, 4, 5, and 6 exceed the programmed threshold limit.

12 V

CC

Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.

13 ALERT

SMBus Alert (Interrupt), Active-Low, Open-Drain Output. ALERT asserts low when the temperature of
channels 1, 4, 5, and 6 exceed programmed threshold limit.

14

SMBus Serial-Data Input/Output. Connect to a pullup resistor.

15 SMBCLK SMBus Serial-Clock Input. Connect to a pullup resistor.

16 GND Ground

SMBDATA

SMBus Digital Interface

From a software perspective, the MAX6698 appears as
a series of 8-bit registers that contain temperature mea­surement 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 same SMBus slave
address also provides access to all functions.

The MAX6698 employs four standard SMBus protocols:
write byte, read byte, send byte, and receive byte
(Figure 2). The shorter receive byte protocol allows
quicker transfers, provided that the correct data regis-

ter 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. Figure
3 is the SMBus write timing diagram and Figure 4 is the
SMBus read timing diagram.

The remote diode 1 measurement channel provides 11
bits of data (1 LSB = 0.125°C). All other temperature­measurement channels provide 8 bits of temperature
data (1 LSB = 1°C). The 8 most significant bits (MSBs)
can be read from the local temperature, remote tem­perature, and thermistor registers. The remaining 3 bits

MAX6698

_______________________________________________________________________________________ 7

DXP1

DXN1

3-TO-1

MUX

INPUT

BUFFER

ADC

10/100µA

V

CC

CNT

COUNTER

VREF

COMMAND BYTE

REMOTE TEMPERATURES

LOCAL TEMPERATURES

REGISTER BANK

ALERT THRESHOLD

OVERT THRESHOLD

ALERT RESPONSE ADDRESS

ALU

DP

VREF1

SMBus

INTERFACE

MAX6698

SCL SDA

OVERT

ALERT

DXP3

DXN3

BUF1

BUF2

3-TO-1

MUX

R

EXT1

R

THER1

R

EXT2

R

THER1

R

EXT1

R

THER1

Figure 1. Internal Block Diagram

7-Channel Precision Remote-Diode, Thermistor,

and Local Temperature Monitor

MAX6698

for remote diode 1 can be read from the extended tem­perature register. If extended resolution is desired, the
extended resolution register should be read first. This
prevents the most significant bits from being overwritten
by new conversion results until they have been read. If
the most significant bits have not been read within an
SMBus timeout period (nominally 25ms), normal updat­ing continues. Table 1 shows themistor voltage data for­mat. Table 2 shows the main temperature register (high
byte) data format. Table 3 shows the extended resolu­tion temperature register (low byte) data format.

Diode Fault Detection

If a channel’s input DXP_ and DXN_ are left open, the
MAX6698 detects a diode fault. An open diode fault
does not cause either ALERT or OVERT to assert. A bit
in the status register for the corresponding channel is
set to 1 and the temperature data for the channel is
stored as all 1s (FFh). It takes approximately 4ms for
the MAX6698 to detect a diode fault. Once a diode fault
is detected, the MAX6698 goes to the next channel in
the conversion sequence. Depending on operating
conditions, a shorted diode may or may not cause
ALERT or OVERT to assert, so if a channel will not be
used, disconnect its DXP and DXN inputs.

Alarm Threshold Registers

There are 11 alarm threshold registers that store over­temperature ALERT and OVERT threshold values.
Seven of these registers are dedicated to store one
local alert temperature threshold limit, three remote alert
temperature threshold limits, and three thermistor volt­age threshold limits (see the

ALERT

Interrupt Mode sec­tion). The remaining four registers are dedicated to
remote-diode channel 1, and three thermistor channels
1, 2, and 3 to store overtemperature threshold limits
(see the

OVERT

Overtemperature Alarm section).
Access to these registers is provided through the
SMBus interface.

7-Channel Precision Remote-Diode, Thermistor,
and Local Temperature Monitor

8 _______________________________________________________________________________________

Figure 2. SMBus Protocols

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)

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

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

S ADDRESS RD ACK DATA /// P

7 bits 8 bits

WRS ACK COMMAND ACK P

8 bits

ADDRESS

7 bits

P

1

ACKDATA

8 bits

ACKCOMMAND

8 bits

ACKWRADDRESS

7 bits

S

S ADDRESS WR ACK COMMAND ACK S ADDRESS

7 bits8 bits7 bits

RD ACK DATA

8 bits

/// P

Table 1. Thermistor Voltage Data Format

V

REXT

1.000 1100 1000

0.500 0110 0100

0.250 0011 0010

0.055 0000 1011

0.050 0000 1010

0.005 0000 0001

0.000 0000 0000

DIGITAL OUTPUT