MAXIM MAX6581 User Manual

19-5260; Rev 0; 8/10

EVALUATION KIT

AVAILABLE

±1°C Accurate 8-Channel Temperature Sensor

General Description

The MAX6581 precision multichannel temperature
sensor monitors its own temperature and the tempera­tures of up to seven external diode-connected transis­tors. All temperature channels have programmable alert
and overtemperature thresholds. When the measured
temperature of a channel crosses the respective thresh­old, a status bit is set in one of the status registers. Two
open-drain alarm outputs (ALERT and OVERT) assert
corresponding to these bits in the status register(s).

Resistance cancellation is available for all channels and
compensates for high series resistance in circuit-board
traces and thermal diodes.

The 2-wire serial interface accepts SMBus™ protocols
(write byte, read byte, send byte, and receive byte) for
reading the temperature data and programming the
alarm thresholds.

The MAX6581 is specified for an operating temperature
range of -40NC to +125NC and is available in a 24-pin,
4mm x 4mm thin QFN package with an exposed pad.

Features

S Eight Channels to Measure Seven Remote and

One Local Temperature

S 11-Bit, 0.125NC Resolution

S High Accuracy of ±1NC (max) from +60NC to

+100NC (Remote Channels)

S -64NC to +150NC Remote Temperature Range

S Programmable Undertemperature/

Overtemperature Alerts

S SMBus/I
S Two Open-Drain Alarm Outputs (ALERT and

2

C-Compatible Interface

OVERT)

S Resistance Cancellation on All Remote Channels

Applications

Desktop Computers

Notebook Computers

Workstations

Servers

Data Communications

MAX6581

Ordering Information/Selector Guide

PART SLAVE ADDRESS PIN-PACKAGE

MAX6581TG9A+ 0X9A 24 TQFN-EP*
MAX6581TG9C+** 0X9C 24 TQFN-EP*
MAX6581TG9E+** 0X9E 24 TQFN-EP*
MAX6581TG98+** 0X98 24 TQFN-EP*

+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
**Future product—contact factory for availability.

Note: These devices operate over the -40NC to +125NC operating temperature range.

Typical Application Circuit appears at end of data sheet.

SMBus is a trademark of Intel Corp.

OPERATING

TEMPERATURE RANGE

-40NC to +125NC -64NC to +150NC

-40NC to +125NC -64NC to +150NC

-40NC to +125NC -64NC to +150NC

-40NC to +125NC -64NC to +150NC

MEASURED

TEMPERATURE RANGE

_______________________________________________________________ Maxim Integrated Products 1

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.

±1°C Accurate 8-Channel Temperature Sensor

ABSOLUTE MAXIMUM RATINGS

(All Voltages Referenced to GND)
V

, SMBCLK, SMBDATA, ALERT,

CC

OVERT, STBY to GND .......................................... -0.3V to +4V

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

DXN_ to GND ........................................... -0.3V to (V

+ 0.3V)

CC

+ 0.3V)

CC

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

DXN_ Current .................................................................... Q1mA

Continuous Power Dissipation (T

MAX6581

= +70NC)

A

24-Pin Thin QFN (derate 27.8mW/NC above +70NC) ..2222mW

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-

layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.

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

(VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Voltage V
Standby Supply Current I

Operating Current

Temperature Resolution

3-Sigma Temperature Accuracy
(Remote Channels 1–7)

3-Sigma Temperature Accuracy
(Local)

6-Sigma Temperature Accuracy
(Remote Channels 1–7)

6-Sigma Temperature Accuracy
(Local)

Supply Sensitivity of
Temperature Accuracy

I

CC1

I

CC2

CC

SS

SMBus static 4 15
During conversion, RC off 500 600
During conversion, RC on 550 650

= 3.3V

V

CC

V

= 3.3V

CC

V

= 3.3V

CC

V

= 3.3V

CC

Package Junction-to-Ambient Thermal Resistance
(B

) (Note 1) ............................................................36.0NC/W

JA

Package Junction-to-Case Thermal Resistance
(B

) (Note 1) ..............................................................3.0NC/W

JC

ESD Protection (all pins, Human Body Model) ...................Q2kV

Operating Temperature Range ........................ -40NC to +125NC

Junction Temperature .....................................................+150NC

Storage Temperature Range .......................... -65NC to +150NC

Lead Temperature (soldering, 10s) ...............................+300NC

Soldering Temperature (reflow) ......................................+260NC

3.0 3.6 V

11 Bits

0.125

T

= +30NC to +85NC,

A

T

= +60NC to +100NC

RJ

, TRJ = -40NC to +125NC

A

T

= +30NC to +85NC,

A

T

= +100NC to +150NC

RJ

= +30NC to +85NC

T

A

= -40NC to +125NC

A

T

= 0NC to +150NC

A

T

= +30NC to +85NC,

A

T

= +60NC to +100NC

RJ

, TRJ = -40NC to +125NC

A

T

= +30NC to +85NC,

A

T

= +100NC to +125NC

RJ

= +30NC to +85NC

T

A

= -40NC to +125NC

A

T

= 0NC to +150NC

A

-0.85 +0.85

-1.2 +1.2

-2.5 +2.5

-1 +1

-2 +2

-3 +3

-1 +1

-2 +2

-2.75 +2.75

-1.5 +1.5

-2.5 +2.5

-3.5 +3.5

Q0.2 NC/V

FA

FA

NC

NCT

NCT

NCT

NCT

2 ______________________________________________________________________________________

±1°C Accurate 8-Channel Temperature Sensor

ELECTRICAL CHARACTERISTICS (continued)

(VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Resistance cancellation mode off 95 125 156

Conversion Time per Channel t

Remote-Diode Source Current I

CONV

RJ

Resistance cancellation mode on or beta
compensation on

High level
Low level 8 10 12

High level

Resistance cancellation
mode off

Resistance cancellation

190 250 312

80 100 120

160 200 240

mode on or beta

Low level 16 20 24

DXP_ and DXN_ Leakage
Current

Standby mode 100 nA

Undervoltage Lockout Threshold UVLO Falling edge of V

compensation on

disables ADC 2.25 2.80 2.95 V

CC

Undervoltage Lockout Hysteresis 90 mV

Power-On-Reset (POR)
Threshold

falling edge 1.3 2.0 2.2 V

V

CC

POR Threshold Hysteresis 90 mV

ALERT and OVERT

I

= 1mA 0.01

Output Low Voltage V

Input Leakage Current I

OL

LEAK

SINK

= 6mA 0.3

I

SINK

-1 +1

SMBus INTERFACE, STBY

Logic Input Low Voltage V
Logic Input High Voltage V

VCC = 3.6V 0.8 V

IL

VCC = 3.0V 2.2 V

IH

Input Leakage Current -1 +1

I

Output Low Voltage V
Input Capacitance C

OL

IN

= 6mA 0.1 V

SINK

5 pF

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

Serial-Clock Frequency f

Bus Free Time Between STOP
and START Condition

SMBCLK

t

BUF

START Condition Setup Time f

Repeated START Condition
Setup Time

START Condition Hold Time t

STOP Condition Setup Time t

Clock Low Period t
Clock High Period t
Data-In Hold Time t
Data-In Setup Time t

t

SU:STA

HD:STA

SU:STO

LOW

HIGH

HD:DAT

SU:DAT

(Note 4) 400 kHz

f

SMBCLK

SMBCLK

90% of SMBCLK to 90% of SMBDATA,
f

SMBCLK

10% of SMBDATA to 90% of SMBCLK,
f

SMBCLK

90% of SMBCLK to 90% of SMBDATA,
f

SMBCLK

10% to 10%, f

= 400kHz 1.6

= 400kHz 0.6

= 400kHz

= 400kHz

= 400kHz

SMBCLK

= 400kHz 1

50 ns

0.6

0.6

90% to 90% 0.6

0 0.9 us

(Note 5) 100 ns

ms

FA

V

FA

FA

Fs

Fs

Fs

Fs

Fs
Fs

MAX6581

_______________________________________________________________________________________ 3

±1°C Accurate 8-Channel Temperature Sensor

ELECTRICAL CHARACTERISTICS (continued)

(VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Receive SMBCLK/SMBDATA
Rise Time

Receive SMBCLK/SMBDATA Fall
Time

MAX6581

Data-Out Hold Time t
Pulse Width of Spike Suppressed t
SMBus Timeout t

Note 2: All parameters are tested at T
Note 3: Timing specifications are guaranteed by design.
Note 4: The serial interface resets when SMBCLK is low for more than t
Note 5: A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SMBCLK’s falling

edge.

Typical Operating Characteristics

(VCC = +3.3V, V

= VCC, TA = +25NC, unless otherwise noted.)

STBY

t

R

t

F

DH

SP

TIMEOUT

= +85NC. Specifications over temperature are guaranteed by design.

A

SMBDATA low period for interface reset 25 37 45 ms

TIMEOUT

.

50 ns

0 50 ns

300 ns

300 ns

STANDBY SUPPLY CURRENT

vs. SUPPLY VOLTAGE

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

STANDBY SUPPLY CURRENT (µA)

HARDWARE OR SOFTWARE

0.5
STANDBY SUPPLY CURRENT

0

3.0 3.6
SUPPLY VOLTAGE (V)

AVERAGE OPERATING SUPPLY CURRENT

vs. SUPPLY VOLTAGE

400

RESISTANCE

395

MAX6581 toc01

3.53.43.33.23.1

CANCELLATION OFF

390

385

380

375

370

365

AVERAGE OPERATING SUPPLY CURRENT (µA)

360

3.0 3.6
SUPPLY VOLTAGE (V)

MAX6581 toc02

3.53.43.1 3.2 3.3

REMOTE-DIODE TEMPERATURE ERROR

vs. REMODE-DIODE TEMPERATURE

10

9
8
7
6
5
4
3
2
1
0

-1

-2

-3

-4

-5

-6

-7

REMOTE-DIODE TEMPERATURE ERROR (°C)

-8

-9

-10

-10 130
REMOTE-DIODE TEMPERATURE (°C)

MAX6581 toc03

1109050 703010

4 ______________________________________________________________________________________

±1°C Accurate 8-Channel Temperature Sensor

Typical Operating Characteristics (continued)

(VCC = +3.3V, V

= VCC, TA = +25NC, unless otherwise noted.)

STBY

MAX6581

LOCAL TEMPERATURE ERROR

vs. DIE TEMPERATURE

5

4

3

2

1

0

-1

-2

-3

LOCAL TEMPERATURE ERROR (°C)

-4

-5

-10 100
DIE TEMPERATURE (°C)

LOCAL TEMPERATURE ERROR

vs. POWER-SUPPLY NOISE FREQUENCY

5

4

3

2

1

0

-1

-2

-3

LOCAL TEMPERATURE ERROR (°C)

-4

-5

0.001 10
POWER-SUPPLY NOISE FREQUENCY (MHz)

100mV

10.10.01

REMOTE-DIODE TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY

5

4

MAX6581 toc04

908060 7010 20 30 40 500

3

2

1

0

-1

-2

-3

-4

REMOTE-DIODE TEMPERATURE ERROR (°C)

-5

0.001 10
POWER-SUPPLY NOISE FREQUENCY (MHz)

100mV

P-P

TRJ = +85°C

10.10.01

MAX6581 toc05

REMOTE-DIODE TEMPERATURE ERROR

vs. CAPACITANCE

P-P

MAX6581 toc06

5

4

3

2

1

0

-1

-2

-3

-4

REMOTE-DIODE TEMPERATURE ERROR (°C)

-5
1 100

CAPACITANCE (nF)

100mV

P-P

TRJ = +85°C

10

MAX6581 toc07

REMOTE-DIODE TEMPERATURE ERROR

vs. RESISTANCE

50

TRJ = +85°C

45

40

35

30

RESISTANCE

25

CANCELLATION OFF

20

15

10

5

REMOTE-DIODE TEMPERATURE ERROR (°C)

0

-5
0 100

RESISTANCE
CANCELLATION ON

RESISTANCE (I)

MAX6581 toc08

908060 7020 30 40 5010

_______________________________________________________________________________________ 5

±1°C Accurate 8-Channel Temperature Sensor

Pin Configuration

MAX6581

TOP VIEW

SMBDATA

SMBCLK

GND

N.C.

DXP1

DXN1

19

20

21

22

23

24

CC

V

ALERT

1718 16 14 13

OVERT

I.C.

STBY

15

MAX6581

*EP

1 2

DXP2

DXN2

*EP = EXPOSED PAD, CONNECT TO GND

3

DXP3

4 5 6

DXP4

DXN3

DXP7

N.C.

12

DXN7

DXP6

11

DXN6

10

9

DXN5

DXP5

8

DXN4

7

Pin Description

PIN NAME FUNCTION

Combined Current Source and ADC Positive Input for Channel 2 Remote Diode. Connect DXP2 to

1 DXP2

the anode of a remote-diode-connected, temperature-sensing transistor. Leave DXP2 unconnected
or connect to DXN2 if a remote diode is not used. Connect a 100pF capacitor between DXP2 and
DXN2 for noise filtering.

Cathode Input for Channel 2 Remote Diode. Connect the cathode of the channel 2 remote-diode-

2 DXN2

connected transistor to DXN2. If the channel 2 remote transistor is a substrate pnp (e.g., on a CPU
die), connect the base of the pnp to DXN2. Leave DXN2 unconnected or connect to DXP2 if a
remote diode is not used. Connect a 100pF capacitor between DXP2 and DXN2 for noise filtering.

Combined Current Source and ADC Positive Input for Channel 3 Remote Diode. Connect DXP3 to

3 DXP3

the anode of a remote-diode-connected, temperature-sensing transistor. Leave DXP3 unconnected
or connect to DXN3 if a remote diode is not used. Connect a 100pF capacitor between DXP3 and
DXN3 for noise filtering.

Cathode Input for Channel 3 Remote Diode. Connect the cathode of the channel 3 remote-diode-

4 DXN3

connected transistor to DXN3. If the channel 3 remote transistor is a substrate pnp (e.g., on a CPU
die), connect the base of the pnp to DXN3. Leave DXN3 unconnected or connect to DXP3 if a
remote diode is not used. Connect a 100pF capacitor between DXP3 and DXN3 for noise filtering.

Combined Current Source and ADC Positive Input for Channel 4 Remote Diode. Connect DXP4 to

5 DXP4

the anode of a remote-diode-connected, temperature-sensing transistor. Leave DXP4 unconnected
or connect to DXN4 if a remote diode is not used. Connect a 100pF capacitor between DXP4 and
DXN4 for noise filtering.

6, 22 N.C. No Connection. Connect to other N.C. or leave unconnected.

6 ______________________________________________________________________________________

±1°C Accurate 8-Channel Temperature Sensor

Pin Description (continued)

PIN NAME FUNCTION

Cathode Input for Channel 4 Remote Diode. Connect the cathode of the channel 4 remote-diode-

7 DXN4

8 DXP5

9 DXN5

10 DXN6

11 DXP6

connected transistor to DXN4. If the channel 4 remote transistor is a substrate pnp (e.g., on a CPU
die), connect the base of the pnp to DXN4. Leave DXN4 unconnected or connect to DXP4 if a
remote diode is not used. Connect a 100pF capacitor between DXP4 and DXN4 for noise filtering.

Combined Current Source and ADC Positive Input for Channel 5 Remote Diode. Connect DXP5 to
the anode of a remote-diode-connected, temperature-sensing transistor. Leave DXP5 unconnected
or connect to DXN5 if a remote diode is not used. Connect a 100pF capacitor between DXP5 and
DXN5 for noise filtering.

Cathode Input for Channel 5 Remote Diode. Connect the cathode of the channel 5 remote-diode­connected transistor to DXN5. If the channel 5 remote transistor is a substrate pnp (e.g., on a CPU
die), connect the base of the pnp to DXN5. Leave DXN5 unconnected or connect to DXP5 if a
remote diode is not used. Connect a 100pF capacitor between DXP5 and DXN5 for noise filtering.

Cathode Input for Channel 6 Remote Diode. Connect the cathode of the channel 6 remote-diode­connected transistor to DXN6. If the channel 6 remote transistor is a substrate pnp (e.g., on a CPU
die), connect the base of the pnp to DXN6. Leave DXN6 unconnected or connect to DXP6 if a
remote diode is not used. Connect a 100pF capacitor between DXP6 and DXN6 for noise filtering.

Combined Current Source and ADC Positive Input for Channel 6 Remote Diode. Connect DXP6 to
the anode of a remote-diode-connected, temperature-sensing transistor. Leave DXP6 unconnected
or connect to DXN6 if a remote diode is not used. Connect a 100pF capacitor between DXP6 and
DXN6 for noise filtering.

MAX6581

Cathode Input for Channel 7 Remote Diode. Connect the cathode of the channel 7 remote-diode-

12 DXN7

13 DXP7

14

15 I.C. Internally Connected. I.C. is internally connected to V

16

17 V

18

19 SMBDATA SMBus Serial-Data Input/Output. Connect SMBDATA to a pullup resistor.
20 SMBCLK SMBus Serial-Clock Input. Connect SMBCLK to a pullup resistor.

STBY

OVERT

CC

ALERT

connected transistor to DXN7. If the channel 7 remote transistor is a substrate pnp (e.g., on a CPU
die), connect the base of the pnp to DXN7. Leave DXN7 unconnected or connect to DXP7 if a
remote diode is not used. Connect a 100pF capacitor between DXP7 and DXN7 for noise filtering.

Combined Current Source and ADC Positive Input for Channel 7 Remote Diode. Connect DXP7 to
the anode of a remote-diode-connected, temperature-sensing transistor. Leave DXP7 unconnected
or connect to DXN7 if a remote diode is not used. Place a 100pF capacitor between DXP7 and
DXN7 for noise filtering.

Active-Low Standby Input. Drive STBY logic-low to place the MAX6581 in standby mode, or logic­high for normal mode. Temperature and threshold data are retained in standby mode.

. Connect I.C. to VCC or leave unconnected.

CC

Overtemperature Active-Low, Open-Drain Output. OVERT asserts low when the temperature of any
remote channel exceeds the programmed threshold limit.

Supply Voltage Input. Bypass to GND with a 0.1FF capacitor.
SMBus Alert (Interrupt), Active-Low, Open-Drain Output. ALERT asserts low when the temperature of

any channel crosses a programmed ALERT high or low threshold.

_______________________________________________________________________________________ 7

±1°C Accurate 8-Channel Temperature Sensor

Pin Description (continued)

PIN NAME FUNCTION

21 GND Ground

Combined Current Source and ADC Positive Input for Channel 1 Remote Diode. Connect DXP1 to

23 DXP1

MAX6581

24 DXN1

— EP Exposed Pad. Connect EP to GND.

the anode of a remote-diode-connected, temperature-sensing transistor. Leave DXP1 unconnected
or connect to DXN1 if a remote diode is not used. Connect a 100pF capacitor between DXP1 and
DXN1 for noise filtering.

Cathode Input for Channel 1 Remote Diode. Connect the cathode of the channel 1 remote-diode­connected transistor to DXN1. If the channel 1 remote transistor is a substrate pnp (e.g., on a CPU
die), connect the base of the pnp to DXN1. Leave DXN1 unconnected or connect to DXP1 if a
remote diode is not used. Connect a 100pF capacitor between DXP1 and DXN1 for noise filtering.

Detailed Description

The MAX6581 is a precision multichannel temperature
monitor that features one local and seven remote tem­perature-sensing channels with a programmable alert
threshold for each temperature channel and a program­mable overtemperature threshold for channels 1–7 (see
Figure 1). Communication with the MAX6581 is achieved
through the SMBus serial interface and a dedicated alert
pin (ALERT). The alarm outputs, (OVERT and ALERT)
assert if the software-programmed temperature thresh­olds are exceeded. ALERT also asserts if the measured
temperature falls below the ALERT low limits. ALERT
typically serves as an interrupt, while OVERT can be
connected to a fan, system shutdown, or other thermal­management circuitry.

ADC Conversion Sequence

The MAX6581 starts the conversion sequence by
measuring the temperature on channel 1, followed by 2,
local channel, 3–7. The conversion result for each active
channel is stored in the corresponding temperature data
register. No conversion is performed on any channel that
does not have a diode.

Low-Power Standby Mode

Enter software-standby mode by setting the STOP
bit to 1 in the Configuration register. Enter hardware­standby by pulling STBY low. Software-standby mode
disables the ADC and reduces the supply current to
approximately 4FA. During either software or hardware
standby, data is retained in memory. During hardware
standby, the SMBus interface is inactive. During software

standby, the SMBus interface is active and listening for
commands. The timeout is enabled if a START condition
is recognized on 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.

Operating-Current Calculation

The MAX6581 operates at different operating-current
levels depending on how many external channels are in
use and how many of those are in resistance cancella­tion (RC) mode. The average operating current is:

N 1 2 N

+ ×

I I I

= + ×

AV CC1 CC2

where:

N

= the number of remote channels that are operating

N

in normal mode.

NR = the number of remote channels that are in RC
mode.

IAV = the average operating power-supply current over a
complete series of conversions.

I

= the average operating power-supply current

CC1

during a conversion in normal mode.

I

= the average operating power-supply current

CC2

during a conversion in RC mode.

N R

N 2 N 1 N 2 N 1

+ × + + × +

N R N R

8 ______________________________________________________________________________________