MAX6581_V01 [MAXIM]
±1°C Accurate 8-Channel Temperature Sensor;
| 型号： | MAX6581_V01 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | ±1°C Accurate 8-Channel Temperature Sensor |
| 文件： | 总27页 (文件大小：1080K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Evaluation Kit
Available
Design
Resources
Tools
and Models
Support
Click here to ask an associate for production status of specific part numbers.
±1°C Accurate 8-Channel
Temperature Sensor
MAX6581
General Description
Features
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 over-
temperature 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).
● Eight Channels to Measure Seven Remote and One
Local Temperature
● 11-Bit, 0.125°C Resolution
● High Accuracy of ±1°C (max) from +60°C to +100°C
(Remote Channels)
● -64°C to +150°C Remote Temperature Range
● Programmable Undertemperature/Overtemperature
Alerts
Resistance cancellation is available for all channels and
compensates for high series resistance in circuit-board
traces and thermal diodes.
2
● SMBus/I C-Compatible Interface
● Two Open-Drain Alarm Outputs (ALERT and OVERT)
● Resistance Cancellation on All Remote Channels
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.
Applications
● Desktop Computers
● Notebook Computers
● Workstations
The MAX6581 is specified for an operating temperature
range of -40°C to +125°C and is available in a 24-pin,
4mm x 4mm thin QFN package with an exposed pad.
● Servers
● Data Communications
Ordering Information/Selector Guide
OPERATING
TEMPERATURE RANGE
MEASURED
TEMPERATURE RANGE
PART
SLAVE ADDRESS
PIN-PACKAGE
MAX6581TG9A+
MAX6581TG9C+
MAX6581TG9E+
MAX6581TG98+
0X9A
0X9C
0X9E
0X98
24 TQFN-EP*
24 TQFN-EP*
24 TQFN-EP*
24 TQFN-EP*
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-64°C to +150°C
-64°C to +150°C
-64°C to +150°C
-64°C to +150°C
Note: All devices are specified over the -40°C to +125°C operating temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Typical Application Circuit appears at end of data sheet.
19-5260; Rev 5; 4/21
©
2021 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners.
One Analog Way, Wilmington, MA 01887 U.S.A.
|
Tel: 781.329.4700
|
© 2021 Analog Devices, Inc. All rights reserved.
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Absolute Maximum Ratings
(All voltages referenced to GND.)
Continuous Power Dissipation (T = +70°C)
A
V
, SMBCLK, SMBDATA, ALERT,
TQFN (derate 27.8mW/°C above +70°C)..................2222mW
CC
OVERT, STBY to GND........................................-0.3V to +4V
ESD Protection (All Pins, Human Body Model) ..................±2kV
Operating Temperature Range......................... -40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range ........................... -65°C to +150°C
Lead Temperature (soldering, 10s) ................................+300°C
Soldering Temperature (reflow).......................................+260°C
DXP_ to GND........................................... -0.3V to (V
DXN_ to GND........................................... -0.3V to (V
SMBDATA, ALERT, OVERT Current.................. -1mA to +50mA
DXN_ Current.....................................................................±1mA
+ 0.3V)
+ 0.3V)
CC
CC
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.
(Note 1)
Package Thermal Characteristics
TQFN
Junction-to-Ambient Thermal Resistance (θ ) ......36.0°C/W
JA
Junction-to-Case Thermal Resistance (θ )..............3.0°C/W
JC
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.maximintegrated.com/thermal-tutorial.
Electrical Characteristics
(V
= +3.0V to +3.6V, T = -40°C to +125°C, unless otherwise noted. Typical values are at V
= +3.3V and T = +25°C.) (Note 2)
CC
A
CC A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
3.6
UNITS
V
Supply Voltage
V
3.0
CC
Standby Supply Current
I
SMBus static
4
500
550
11
15
µA
SS
I
I
During conversion, RC off
600
650
CC1
Operating Current
µA
During conversion, RC on
CC2
Bits
°C
Temperature Resolution
0.125
T
T
= +30°C to +85°C,
A
-0.85
-1.2
+0.85
+1.2
+2.5
= +60°C to +100°C
RJ
3-Sigma Temperature Accuracy
(Remote Channels 1–7)
V
V
V
V
= 3.3V T , T = -40°C to +125°C
°C
°C
°C
°C
CC
CC
CC
CC
A
RJ
T
T
= +30°C to +85°C,
= +100°C to +150°C
A
-2.5
RJ
T
T
T
= +30°C to +85°C
= -40°C to +125°C
= 0°C to +150°C
= +30°C to +85°C,
-1
-2
-3
+1
+2
+3
A
A
A
3-Sigma Temperature Accuracy
(Local)
= 3.3V
T
T
A
-1
-2
+1
+2
= +60°C to +100°C
RJ
6-Sigma Temperature Accuracy
(Remote Channels 1–7)
= 3.3V T , T = -40°C to +125°C
A
RJ
T
T
= +30°C to +85°C,
= +100°C to +125°C
A
-2.75
+2.75
RJ
T
T
T
= +30°C to +85°C
= -40°C to +125°C
= 0°C to +150°C
-1.5
-2.5
-3.5
+1.5
+2.5
+3.5
A
A
A
6-Sigma Temperature Accuracy
(Local)
= 3.3V
Analog Devices
│ 2
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Electrical Characteristics (continued)
(V
= +3.0V to +3.6V, T = -40°C to +125°C, unless otherwise noted. Typical values are at V
= +3.3V and T = +25°C.) (Note 2)
CC
A
CC A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
±0.2
125
250
MAX
UNITS
Supply Sensitivity of Temperature
Accuracy
°C/V
Resistance cancellation mode off
95
156
312
Conversion Time per Channel
t
ms
µA
Resistance cancellation mode on or beta
compensation on
CONV
190
High level
Low level
80
8
100
10
120
12
Resistance cancellation
mode off
Remote-Diode Source Current
I
RJ
Resistance cancellation
mode on or beta
compensation on
High level
160
16
200
20
240
24
Low level
DXP_ and DXN_ Leakage Current
Undervoltage Lockout Threshold
Undervoltage Lockout Hysteresis
Standby mode
100
nA
V
UVLO
Falling edge of V
disables ADC
2.25
1.3
2.80
90
2.95
CC
mV
Power-On-Reset (POR)
Threshold
V
falling edge
2.0
90
2.2
V
CC
POR Threshold Hysteresis
mV
ALERT and OVERT
I
I
= 1mA
= 6mA
0.01
0.3
+1
SINK
SINK
Output Low Voltage
V
V
OL
Input Leakage Current
SMBus INTERFACE, STBY
Logic Input Low Voltage
Logic Input High Voltage
Input Leakage Current
Output Low Voltage
I
-1
µA
LEAK
V
V
V
= 3.6V
= 3.0V
0.8
V
V
IL
CC
V
2.2
-1
IH
CC
+1
µA
V
V
I
= 6mA
0.1
OL
SINK
Input Capacitance
C
5
pF
IN
SMBus-COMPATIBLE TIMING (Figures 3 and 4) (Note 3)
Serial-Clock Frequency
f
(Note 4)
400
kHz
µs
SMBCLK
Bus Free Time Between STOP
and START Condition
t
f
= 400kHz
1.6
0.6
50
BUF
SMBCLK
SMBCLK
START Condition Setup Time
f
= 400kHz
µs
Repeated START Condition
Setup Time
90% of SMBCLK to 90% of SMBDATA,
= 400kHz
t
ns
SU:STA
HD:STA
f
SMBCLK
10% of SMBDATA to 90% of SMBCLK,
= 400kHz
START Condition Hold Time
STOP Condition Setup Time
t
0.6
0.6
µs
µs
f
SMBCLK
90% of SMBCLK to 90% of SMBDATA,
= 400kHz
t
SU:STO
f
SMBCLK
Clock Low Period
Clock High Period
Data-In Hold Time
Data-In Setup Time
t
10% to 10%, f
90% to 90%
= 400kHz
SMBCLK
1
0.6
0
µs
µs
µs
ns
LOW
t
HIGH
HD:DAT
t
0.9
t
(Note 5)
100
SU:DAT
Analog Devices
│ 3
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Electrical Characteristics (continued)
(V
= +3.0V to +3.6V, T = -40°C to +125°C, unless otherwise noted. Typical values are at V
= +3.3V and T = +25°C.) (Note 2)
CC
A
CC A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Receive SMBCLK/SMBDATA
Rise Time
t
300
ns
R
Receive SMBCLK/SMBDATA Fall
Time
t
300
ns
F
Data-Out Hold Time
t
50
0
ns
ns
DH
Pulse Width of Spike Suppressed
SMBus Timeout
t
50
45
SP
TIMEOUT
t
SMBDATA low period for interface reset
25
37
ms
Note 2: All parameters are tested at T = +85°C. Specifications over temperature are guaranteed by design.
A
Note 3: Timing specifications are guaranteed by design.
Note 4: The serial interface resets when SMBCLK is low for more than t
.
TIMEOUT
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
(V
= +3.3V, V
= V , T = +25°C, unless otherwise noted.)
CC
STBY CC A
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
AVERAGE OPERATING SUPPLY CURRENT
vs. SUPPLY VOLTAGE
REMOTE-DIODE TEMPERATURE ERROR
vs. REMODE-DIODE TEMPERATURE
10
9
5.0
400
395
390
385
380
375
370
365
360
RESISTANCE
CANCELLATION OFF
8
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
7
6
5
4
3
2
1
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
HARDWARE OR SOFTWARE
STANDBY SUPPLY CURRENT
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.0
3.1
3.2
3.3
3.4
3.5
3.6
-10
10
30
50
70
90 110 130
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
REMOTE-DIODE TEMPERATURE (°C)
Analog Devices
│ 4
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Typical Operating Characteristics (continued)
(V
= +3.3V, V
= V , T = +25°C, unless otherwise noted.)
CC
STBY CC A
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
REMOTE-DIODE TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
5
4
5
4
100mV
P-P
= +85°C
T
RJ
3
3
2
2
1
1
0
0
-1
-2
-3
-4
-1
-2
-3
-4
-5
-5
-10
0
10 20 30 40 50 60 70 80 90 100
DIE TEMPERATURE (°C)
0.001
0.01
0.1
1
10
POWER-SUPPLY NOISE FREQUENCY (MHz)
LOCAL TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
REMOTE-DIODE TEMPERATURE ERROR
vs. CAPACITANCE
5
4
5
4
100mV
P-P
100mV
P-P
T
= +85°C
RJ
3
3
2
2
1
1
0
0
-1
-2
-3
-4
-5
-1
-2
-3
-4
-5
0.001
0.01
0.1
1
10
1
10
CAPACITANCE (nF)
100
POWER-SUPPLY NOISE FREQUENCY (MHz)
REMOTE-DIODE TEMPERATURE ERROR
vs. RESISTANCE
50
45
40
35
30
25
20
15
10
5
T
= +85°C
RJ
RESISTANCE
CANCELLATION OFF
RESISTANCE
CANCELLATION ON
0
-5
0
10 20 30 40 50 60 70 80 90 100
RESISTANCE (Ω)
Analog Devices
│ 5
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Pin Configuration
TOP VIEW
18
17
16
15
14
13
12
11
10
9
SMBDATA 19
DXN7
DXP6
DXN6
SMBCLK 20
GND 21
MAX6581
N.C. 22
DXN5
DXP5
DXN4
DXP1
DXN1
8
23
24
*EP
5
7
1
2
3
4
6
*EP = EXPOSED PAD, CONNECT TO GND
Pin Description
PIN
NAME
FUNCTION
Combined Current Source and ADC Positive Input for Channel 2 Remote Diode. Connect DXP2 to
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.
1
DXP2
Cathode Input for Channel 2 Remote Diode. Connect the cathode of the channel 2 remote-diode-
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.
2
3
4
DXN2
DXP3
DXN3
Combined Current Source and ADC Positive Input for Channel 3 Remote Diode. Connect DXP3 to
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-
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
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.
5
DXP4
N.C.
6, 22
No Connection. Connect to other N.C. or leave unconnected.
Analog Devices
│ 6
www.analog.com
MAX6581
±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-
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.
7
DXN4
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.
8
DXP5
DXN5
DXN6
DXP6
DXN7
DXP7
Cathode Input for Channel 5 Remote Diode. Connect the cathode of the channel 5 remote-diode-
connected 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.
9
Cathode Input for Channel 6 Remote Diode. Connect the cathode of the channel 6 remote-diode-
connected 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.
10
11
12
13
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.
Cathode Input for Channel 7 Remote Diode. Connect the cathode of the channel 7 remote-diode-
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 logic-high
for normal mode. Temperature and threshold data are retained in standby mode.
14
15
16
17
18
STBY
I.C.
Internally Connected. I.C. is internally connected to V . Connect I.C. to V
or leave unconnected.
CC
CC
Overtemperature Active-Low, Open-Drain Output. OVERT asserts low when the temperature of any
remote channel exceeds the programmed threshold limit.
OVERT
V
Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.
CC
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.
ALERT
19
20
SMBDATA SMBus Serial-Data Input/Output. Connect SMBDATA to a pullup resistor.
SMBCLK SMBus Serial-Clock Input. Connect SMBCLK to a pullup resistor.
Analog Devices
│ 7
www.analog.com
MAX6581
±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
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.
23
DXP1
Cathode Input for Channel 1 Remote Diode. Connect the cathode of the channel 1 remote-diode-
connected 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.
24
—
DXN1
EP
Exposed Pad. Connect EP to GND.
interface is inactive. During software standby, the SMBus
Detailed Description
interface is active and listening for commands. The time-
out 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 inter-
rupted, and the temperature registers are not updated.
The previous data is not changed and remains available.
The MAX6581 is a precision multichannel tempera-
ture monitor that features one local and seven remote
temperature-sensing channels with a programmable alert
threshold for each temperature channel and a program-
mable 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 thresh-
olds 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 thermal-
management circuitry.
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
R
N + 2×N +1
N R
N
I
=
I
+
×I
CC2
AV
CC1
N
+ 2×N +1
N
R
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.
where:
= the number of remote channels that are operating
in normal mode.
N
N
N = the number of remote channels that are in RC mode.
R
I
= the average operating power-supply current over a
AV
complete series of conversions.
Low-Power Standby Mode
I
= the average operating power-supply current
CC1
Enter software-standby mode by setting the STOP bit to
1 in the Configuration register. Enter hardware-standby
by pulling STBY low. Software-standby mode disables
the ADC and reduces the supply current to approximately
4µA. During either software or hardware standby, data is
retained in memory. During hardware standby, the SMBus
during a conversion in normal mode.
I
= the average operating power-supply current
CC2
during a conversion in RC mode.
Analog Devices
│ 8
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
V
CC
DXP1
MAX6581
DXN1
DXP2
I
RJ
OVERT
ALERT
ALARM
ALU
DXN2
DXP3
DXN3
DXP4
+
-
REGISTER BANK
COMMAND BYTE
INPUT
BUFFER
COUNT
DXN4
DXP5
REMOTE TEMPERATURES
LOCAL TEMPERATURES
COUNTER
ALERT THRESHOLD
OVERT THRESHOLD
REF
DXN5
DXP6
ALERT RESPONSE ADDRESS
SMBus INTERFACE
DXN6
DXP7
STBY
DXN7
LOCAL
TRANSISTOR
SMBCLK
SMBDATA
Figure 1. Internal Block Diagram
Analog Devices
│ 9
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
ing the first master. Figure 3 is the SMBus write timing
diagram and Figure 4 is the SMBus read timing diagram.
SMBus Digital Interface
From a software perspective, the MAX6581 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 inter-
face 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 remote-diode-measurement channels provide
11 bits of data (1 LSB = 0.125°C). The eight most
significant bits (MSBs) can be read from the local tem-
perature and remote temperature registers. The remain-
ing 3 bits for remote can be read from the extended
temperature register. If extended resolution is desired,
the extended-resolution register should be read first. This
prevents the MSBs from being overwritten by new conver-
sion results until they have been read. If the MSBs have
not been read within a SMBus timeout period (nominally
37ms), normal updating continues. Table 1 shows the
main temperature register (high-byte) data format and
Table 2 shows the extended-resolution register (low-byte)
data format.
The MAX6581 employs four standard SMBus protocols:
writebyte,readbyte,sendbyte,andreceivebyte(Figure2).
The shorter receive-byte protocol allows quicker trans-
fers, 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 inform-
WRITE-BYTE FORMAT
S
ADDRESS
WR
ACK
COMMAND
ACK
DATA
ACK
P
7 BITS
8 BITS
8 BITS
1
SLAVE ADDRESS: EQUIVALENT
TO CHIP-SELECT LINE OF
A 3-WIRE INTERFACE
DATA BYTE: DATA GOES INTO THE REGISTER
SET BY THE COMMAND BYTE (TO SET
THRESHOLDS, CONFIGURATION MASKS, AND
SAMPLING RATE)
READ-BYTE FORMAT
S
ADDRESS
WR
ACK
COMMAND
ACK
S
ADDRESS
7 BITS
RD
ACK
DATA
///
P
7 BITS
8 BITS
8 BITS
SLAVE ADDRESS: EQUIVALENT
TO CHIP SELECT LINE
COMMAND BYTE: SELECTS
WHICH REGISTER YOU ARE
READING FROM
SLAVE ADDRESS: REPEATED
DUE TO CHANGE IN DATA-
FLOW DIRECTION
DATA BYTE: READS FROM
THE REGISTER SET BY THE
COMMAND BYTE
SEND-BYTE FORMAT
RECEIVE-BYTE FORMAT
S
ADDRESS
WR
ACK
COMMAND
ACK
P
S
ADDRESS
RD
ACK
DATA
///
P
7 BITS
8 BITS
7 BITS
8 BITS
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
Figure 2. SMBus Protocols
Analog Devices
│ 10
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
A
B
C
D
E
F
G
H
I
J
K
L
M
t
t
HIGH
LOW
SMBCLK
SMBDATA
t
t
SU:STO BUF
t
t
t
SU:DAT
SU:STA HD:STA
A = START CONDITION
E = SLAVE PULLS SMBDATA LINE LOW
I = SLAVE PULLS DATA LINE LOW
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
Figure 3. SMBus Write Timing Diagram
A
B
C
D
E
F
G
H
I
J
K
t
t
HIGH
LOW
SMBCLK
SMBDATA
t
t
t
t
HD:DAT
HD:STA
SU:STA
SU:DAT
t
t
SU:STO
BUF
A = START CONDITION
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = ACKNOWLEDGE CLOCK PULSE
J = STOP CONDITION
K = NEW 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
Figure 4. Read-Timing Diagram
Analog Devices
│ 11
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Table 1. Main Temperature Register (High-Byte) Data Format
DIGITAL OUTPUT
TEMPERATURE (°C)
NORMAL FORMAT
EXTRANGE = 0
EXTENDED FORMAT
EXTRANGE = 1
Diode fault (open or short)
1111 1111
1111 1111
1111 1110
1011 1111
1011 1110
0111 1101
0101 0101
0001 1001
0000 0000
0000 0000
0000 0000
0000 0000
0000 0000
0000 0000
1111 1111
1111 1111
1111 1111
1111 1111
1111 1110
1011 1101
1001 0101
0101 1001
0100 0000
0011 1111
0001 1000
0000 0001
0000 0000
0000 0000
> +254
+254
+191
+190
+125
+85
+25
0
-1
-40
-63
-64
< -64
Table 2. Extended-Resolution Temperature Register (Low-Byte) Data Format
TEMPERATURE (°C)
0
DIGITAL OUTPUT
000X XXXX
001X XXXX
010X XXXX
011X XXXX
100X XXXX
101X XXXX
110X XXXX
111X XXXX
+0.125
+0.250
+0.375
+0.500
+0.625
+0.750
+0.875
X = Don’t care.
Analog Devices
│ 12
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Table 3. Command Byte Register Bit Assignment
POR
VALUE
(HEX)
ADDRESS
(HEX)
READ/
WRITE
REGISTER
DESCRIPTION
Remote 1
01
02
03
04
05
06
07
08
00
00
00
00
00
00
00
00
R
R
R
R
R
R
R
R
Read channel 1 remote temperature
Remote 2
Remote 3
Remote 4
Remote 5
Remote 6
Local
Read channel 2 remote temperature
Read channel 3 remote temperature
Read channel 4 remote temperature
Read channel 5 remote temperature
Read channel 6 remote temperature
Read local temperature
Remote 7
Read channel 7 remote temperature
Remote 1 Extended
Bits*
09
00
R
Read channel 1 remote-diode extended temperature
Manufacturer ID
Revision ID
0A
0F
4D
00
R
R
Read manufacturer ID
Read revision ID
Remote 1 ALERT High
Limit
Read/write channel 1 remote-diode alert high-temperature
threshold limit
11
12
13
14
15
7F
7F
64
64
64
R/W
R/W
R/W
R/W
R/W
Remote 2 ALERT High
Limit
Read/write channel 2 remote-diode alert high-temperature
threshold limit
Remote 3 ALERT High
Limit
Read/write channel 3 remote-diode alert high-temperature
threshold limit
Remote 4 ALERT High
Limit
Read/write channel 4 remote-diode alert high-temperature
threshold limit
Remote 5 ALERT High
Limit
Read/write channel 5 remote-diode alert high-temperature
threshold limit
Remote 6 ALERT High
Limit
Read/write channel 6 remote-diode alert high-temperature
threshold limit
16
17
18
20
21
64
5A
64
50
6E
R/W
R/W
R/W
R/W
R/W
Local ALERT High Limit
Read/write local-diode alert high-temperature threshold limit
Remote 7 ALERT High
Limit
Read/write channel 7 remote-diode alert high-temperature
threshold limit
Local OVERT High Limit
Remote 1 OVERT High
Read/write channel local-diode overtemperature threshold limit
Read/write channel 1 remote-diode overtemperature threshold limit
Limit
Remote 2 OVERT High
Limit
22
23
24
25
26
6E
6E
7F
5A
5A
R/W
R/W
R/W
R/W
R/W
Read/write channel 2 remote-diode overtemperature threshold limit
Read/write channel 3 remote-diode overtemperature threshold limit
Read/write channel 4 remote-diode overtemperature threshold limit
Read/write channel 5 remote-diode overtemperature threshold limit
Read/write channel 6 remote-diode overtemperature threshold limit
Remote 3 OVERT High
Limit
Remote 4 OVERT High
Limit
Remote 5 OVERT High
Limit
Remote 6 OVERT High
Limit
Analog Devices
│ 13
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Table 3. Command Byte Register Bit Assignment (continued)
POR
VALUE
(HEX)
ADDRESS
(HEX)
READ/
WRITE
REGISTER
DESCRIPTION
Remote 7 OVERT High
Limit
27
30
5A
00
R/W
R/W
Read/write channel 7 remote-diode overtemperature threshold limit
Read/write all channels alert low-temperature threshold limit
ALERT Low Limits (all
channels)
Configuration
41
42
43
44
45
46
47
48
4A
4B
00
00
00
00
00
00
00
FF
00
00
R/W
R/W
R/W
R
Read/write configuration
ALERT Mask
OVERT Mask
ALERT High Status
OVERT Status
Diode Fault Status
ALERT Low Status
ALERT Low Disable
Resistance Cancellation
Transistor Ideality
Read/write ALERT mask
Read/write OVERT mask
Read ALERT high status
Read OVERT status
R
R
Read diode fault status
R
Read ALERT low status
R/W
R/W
R/W
Read/write ALERT low disable
Read/write resistance cancellation enable bits (1 = On, 0 = Off)
Read/write ideality value for remote-sense transistor
Read/write ideality value selection bits (1 = selected transistor
ideality, 0 = 1.008)
Ideality Select
Offset
4C
4D
4E
00
00
00
R/W
R/W
R/W
Read/write temperature offset value
Read/write offset value selection bits (1 = value in Offset register,
0 = 0)
Offset Select
Remote 1 Extended
Bits*
51
00
R
Read channel 1 remote extended temperature
Remote 2 Extended Bits
Remote 3 Extended Bits
Remote 4 Extended Bits
Remote 5 Extended Bits
Remote 6 Extended Bits
Local Extended Bits
52
53
54
55
56
57
58
00
00
00
00
00
00
00
R
R
R
R
R
R
R
Read channel 2 remote extended temperature
Read channel 3 remote extended temperature
Read channel 4 remote extended temperature
Read channel 5 remote extended temperature
Read channel 6 remote extended temperature
Read local channel extended temperature
Read channel 7 remote extended temperature
Remote 7 Extended Bits
*Duplicate entries.
Analog Devices
│ 14
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
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 acknowl-
edgment 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 output latch. If the condi-
tion that caused the alert still exists, the MAX6581 reas-
serts the ALERT interrupt at the end of the next conversion.
Diode Fault Detection
If a channel’s input DXP_ and DXN_ are left open or are
shorted, the MAX6581 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 chan-
nel is stored as all 1s (FFh). It takes approximately 4ms
for the MAX6581 to detect a diode fault. Once a diode
fault is detected, the MAX6581 goes to the next channel
in the conversion sequence.
OVERT Overtemperature Alarms
The MAX6581 has eight overtemperature registers that
store alarm threshold data for the OVERT output. OVERT
is asserted when a channel’s measured temperature is
greater than the value stored in the corresponding thresh-
old register. OVERT remains asserted until the tempera-
ture drops below the programmed threshold minus 4°C
hysteresis. An overtemperature output can be used to
activate a cooling fan, send a warning, initiate clock throt-
tling, or trigger a system shutdown to prevent component
damage. See Table 3 for the POR state of the overtem-
perature threshold registers.
Alarm Threshold Registers
There are 17 alarm threshold registers that store over-
temperature and undertemperature ALERT and OVERT
threshold values. Nine of these registers are dedicated
to storing one local alert overtemperature threshold limit,
seven remote alert overtemperature threshold limits, and
one shared alert undertemperature temperature thresh-
old limit (see the ALERT Interrupt Mode section). The
remaining eight registers are dedicated to storing one
local overtemperature threshold limit and seven remote
channels to store overtemperature threshold limits (see
the OVERT Overtemperature Alarms section). Access to
these registers is provided through the SMBus interface.
Command Byte Register Functions
The 8-bit Command Byte register (Table 3) is the master
index that points to the various other registers within the
MAX6581. This register’s POR state is 0000 0000 (00h).
ALERT Interrupt Mode
ALERT interrupts occur when the internal or external tem-
perature reading exceeds a high-temperature limit (user
programmable) or a low-temperature limit. The ALERT
interrupt output signal can be cleared by reading the sta-
tus register(s) associated with the fault(s) or by success-
fully responding to an alert response address transmis-
sion by the master. In both cases, the alert is cleared but
is reasserted at the end of the next conversion if the fault
condition still exists. The interrupt does not halt automatic
conversions. The ALERT output is open-drain so that
multiple devices can share a common interrupt line. All
ALERT interrupts can be masked using the ALERT Mask
register (42h). The POR state of these registers is shown
in Table 3.
Configuration Register (41h)
The Configuration register (Table 4) has several
functions. Bit 7 (MSB) is used to put the MAX6581
either in software-standby mode (STOP) or continuous-
conversion mode. Bit 6 resets all registers to their POR
conditions and then clears itself. Bit 5 disables the SMBus
timeout. Bit 1 sets the extended range of the remote tem-
perature diodes. The remaining bits of the Configuration
register are not used. The POR state of this register is
0000 0000 (00h).
ALERT Mask Register (42h)
The ALERT Mask register functions are described
in Table 5. Bits [7:0] are used to mask the ALERT
interrupt output. Bit 6 masks the local alert interrupt and
the remaining bits mask the remote alert interrupts. The
power-up state of this register is 0000 0000 (00h).
ALERT Responses Address
The SMBus alert response interrupt pointer provides
quick fault identification for simple slave devices that lack
the complex logic necessary to be a bus master. Upon
receiving an interrupt signal, the host master can broad-
cast a receive-byte transmission to the alert response
slave address (19h). Then, any slave device that gener-
ated an interrupt attempts to identify itself by putting its
own address on the bus.
OVERT Mask Register (43h)
Table 6 describes the OVERT Mask register. Bit 7 and
the remaining bits mask the OVERT interrupt output for
all channels. The power-up state of this register is 0000
0000 (00h).
The alert response can activate several different slave
2
devices simultaneously, similar to the I C general call. If
Analog Devices
│ 15
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Table 4. Configuration Register (41h)
POR
VALUE
BIT
7 (MSB)
6
NAME
STOP
POR
FUNCTION
Standby-Mode Control Bit. If STOP is set to logic 1, the MAX6581 stops converting and
enters standby mode.
0
0
Reset Bit. Set to logic 1 to put the device into its power-on state. This bit is self-clearing.
5
4
3
2
TIMEOUT
RESERVED
RESERVED
RESERVED
0
0
0
0
Timeout Enable Bit. Set to logic 0 to enable SMBus timeout.
Reserved. Must be set to 0.
Reserved. Must be set to 0.
Reserved. Must be set to 0.
Extended-Range Enable Bit. Set bit 1 to logic 1 to set the temperature and limit data
range to -64°C to +191°C. Set bit 1 to logic 0 to set the range to 0°C to +255°C.
1
0
EXTRANGE
RESERVED
0
0
Reserved. Must be set to 0.
Table 5. ALERT Mask Register (42h)
POR
VALUE
BIT
7 (MSB)
6
NAME
FUNCTION
Mask ALERT 7
0
Channel 7 Alert Mask. Set to logic 1 to mask channel 7 ALERT.
Local Alert Mask. Set to logic 1 to mask local channel ALERT.
Mask Local
ALERT
0
5
4
3
2
1
0
Mask ALERT 6
Mask ALERT 5
Mask ALERT 4
Mask ALERT 3
Mask ALERT 2
Mask ALERT 1
0
0
0
0
0
0
Channel 6 Alert Mask. Set to logic 1 to mask channel 6 ALERT.
Channel 5 Alert Mask. Set to logic 1 to mask channel 5 ALERT.
Channel 4 Alert Mask. Set to logic 1 to mask channel 4 ALERT.
Channel 3 Alert Mask. Set to logic 1 to mask channel 3 ALERT.
Channel 2 Alert Mask. Set to logic 1 to mask channel 2 ALERT.
Channel 1 Alert Mask. Set to logic 1 to mask channel 1 ALERT.
Table 6. OVERT Mask Register (43h)
POR
VALUE
BIT
NAME
FUNCTION
Mask Local
OVERT
7 (MSB)
6
0
0
Local Overt Mask. Set to logic 1 to mask local channel OVERT.
Mask OVERT 7
Channel 7 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 7 OVERT.
5
4
3
2
1
0
Mask OVERT 6
Mask OVERT 5
Mask OVERT 4
Mask OVERT 3
Mask OVERT 2
Mask OVERT 1
0
0
0
0
0
0
Channel 6 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 6 OVERT.
Channel 5 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 5 OVERT.
Channel 4 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 4 OVERT.
Channel 3 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 3 OVERT.
Channel 2 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 2 OVERT.
Channel 1 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 1 OVERT.
Analog Devices
│ 16
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
the fault is corrected, either by a drop in the measured
temperature or a change in the threshold temperature.
Status Register Functions
There are four status registers (see Tables 7–10). The
ALERT High Status register indicates whether a mea-
sured local or remote temperature has exceeded the
associated threshold limit set in an ALERT High Limit
register. The OVERT Status register indicates whether
a measured temperature has exceeded the associated
threshold limit set in an OVERT High Limit register. The
Diode Fault Status register indicates whether there is a
diode fault (open or short) in any of the remote-sensing
channels. The ALERT Low Status register indicates
whether the measured temperature has fallen below the
threshold limit set in the ALERT Low Limits register for the
local or remote-sensing diodes.
The ALERT interrupt output follows the status flag bit.
Once the ALERT output is asserted, it can be deasserted
by either reading the ALERT High Status register or by
successfully responding to an alert response address. In
both cases, the alert is cleared even if the fault condition
exists, but the ALERT output reasserts at the end of the
next conversion.
The bits indicating OVERT faults clear only when the
measured temperature drops below the temperature
threshold minus the hysteresis value (4°C), or when the
trip temperature is set to a value at least 4°C above the
current temperature.
Bits in the alert status registers are cleared by a success-
ful read, but set again after the next conversion unless
Table 7. ALERT High Status Register (44h)
POR
STATE
BIT
NAME
FUNCTION
Channel 7 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the channel 7
remote-diode temperature exceeds the programmed temperature threshold limit in the
Remote 7 ALERT High Limit register.
Remote ALERT
7 (MSB)
0
High 7
Local ALERT
Local Channel High-Alert Bit. This bit is set to logic 1 when the local temperature
exceeds the temperature threshold limit in the Local ALERT High Limit register.
6
5
0
0
High
Channel 6 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the channel 6
remote-diode temperature exceeds the programmed temperature threshold limit in the
Remote 6 ALERT High Limit register.
Remote ALERT
High 6
Channel 5 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the channel 5
remote-diode temperature exceeds the programmed temperature threshold limit in the
Remote 5 ALERT High Limit register.
Remote ALERT
4
3
2
1
0
0
0
0
0
0
High 5
Channel 4 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the channel 4
remote-diode temperature exceeds the programmed temperature threshold limit in the
Remote 4 ALERT High Limit register.
Remote ALERT
High 4
Channel 3 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the channel 3
remote-diode temperature exceeds the programmed temperature threshold limit in the
Remote 3 ALERT High Limit register.
Remote ALERT
High 3
Channel 2 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the channel 2
remote-diode temperature exceeds the programmed temperature threshold limit in the
Remote 2 ALERT High Limit register.
Remote ALERT
High 2
Channel 1 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the channel 1
remote-diode temperature exceeds the programmed temperature threshold limit in the
Remote 1 ALERT High Limit register.
Remote ALERT
High 1
Analog Devices
│ 17
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Table 8. OVERT Status Register (45h)
POR
STATE
BIT
NAME
FUNCTION
Local Channel Overtemperature Status Bit. This bit is set to logic 1 when the local
temperature exceeds the temperature threshold limit in the Local OVERT High Limit
register.
7 (MSB)
Local OVERT
0
Channel 7 Remote-Diode Overtemperature Status Bit. This bit is set to logic 1 when
the channel 7 remote-diode temperature exceeds the temperature threshold limit in the
Remote 7 OVERT High Limit register.
6
5
4
3
2
1
0
Remote OVERT 7
Remote OVERT 6
Remote OVERT 5
Remote OVERT 4
Remote OVERT 3
Remote OVERT 2
Remote OVERT 1
0
0
0
0
0
0
0
Channel 6 Remote-Diode Overtemperature Status Bit. This bit is set to logic 1 when
the channel 6 remote-diode temperature exceeds the temperature threshold limit in the
Remote 6 OVERT High Limit register.
Channel 5 Remote-Diode Overtemperature Status Bit. This bit is set to logic 1 when
the channel 5 remote-diode temperature exceeds the temperature threshold limit in the
Remote 5 OVERT High Limit register.
Channel 4 Remote-Diode Overtemperature Status Bit. This bit is set to logic 1 when
the channel 4 remote-diode temperature exceeds the temperature threshold limit in the
Remote 4 OVERT High Limit register.
Channel 3 Remote-Diode Overtemperature Status Bit. This bit is set to logic 1 when
the channel 3 remote-diode temperature exceeds the temperature threshold limit in the
Remote 3 OVERT High Limit register.
Channel 2 Remote-Diode Overtemperature Status Bit. This bit is set to logic 1 when
the channel 2 remote-diode temperature exceeds the temperature threshold limit in the
Remote 2 OVERT High Limit register.
Channel 1 Remote-Diode Overtemperature Status Bit. This bit is set to logic 1 when
the channel 1 remote-diode temperature exceeds the temperature threshold limit in the
Remote 1 OVERT High Limit register.
Table 9. Diode Fault Status Register (46h)
POR
STATE
BIT
7 (MSB)
6
NAME
FUNCTION
RESERVED
Diode Fault 7
0
—
Channel 7 Remote-Diode Fault Bit. This bit is set to 1 when DXP7 and DXN7 are open
circuit or when DXP7 is connected to V
0
0
0
0
0
0
0
.
CC
Channel 6 Remote-Diode Fault Bit. This bit is set to 1 when DXP6 and DXN6 are open
circuit or when DXP6 is connected to V
5
4
3
2
1
0
Diode Fault 6
Diode Fault 5
Diode Fault 4
Diode Fault 3
Diode Fault 2
Diode Fault 1
.
CC
Channel 5 Remote-Diode Fault Bit. This bit is set to 1 when DXP5 and DXN5 are open
circuit or when DXP5 is connected to V
.
CC
Channel 4 Remote-Diode Fault Bit. This bit is set to 1 when DXP4 and DXN4 are open
circuit or when DXP4 is connected to V
.
CC
Channel 3 Remote-Diode Fault Bit. This bit is set to 1 when DXP3 and DXN3 are open
circuit or when DXP3 is connected to V
.
CC
Channel 2 Remote-Diode Fault Bit. This bit is set to 1 when DXP2 and DXN2 are open
circuit or when DXP2 is connected to V
.
CC
Channel 1 Remote-Diode Fault Bit. This bit is set to 1 when DXP1 and DXN1 are open
circuit or when DXP1 is connected to V
.
CC
Analog Devices
│ 18
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Table 10. ALERT Low Status Register (47h)
POR
STATE
BIT
NAME
FUNCTION
Channel 7 Remote-Diode Low-Alert Bit. This bit is set to logic 1 when the channel 7
remote-diode temperature falls below the programmed temperature threshold limit in
the Remote 7 ALERT Low Limit register.
Remote ALERT
7 (MSB)
0
Low 7
Local Channel Remote-Diode Low-Alert Bit. This bit is set to logic 1 when the local
channel remote-diode temperature falls below the programmed temperature threshold
limit in the Local ALERT Low Limit register.
6
5
4
3
2
1
0
Local ALERT Low
0
0
0
0
0
0
0
Channel 6 Remote-Diode Low-Alert Bit. This bit is set to logic 1 when the channel 6
remote-diode temperature falls below the programmed temperature threshold limit in
the Remote 6 ALERT Low Limit register.
Remote ALERT
Low 6
Channel 5 Remote-Diode Low-Alert Bit. This bit is set to logic 1 when the channel 5
remote-diode temperature falls below the programmed temperature threshold limit in
the Remote 5 ALERT Low Limit register.
Remote ALERT
Low 5
Channel 4 Remote-Diode Low-Alert Bit. This bit is set to logic 1 when the channel 4
remote-diode temperature falls below the programmed temperature threshold limit in
the Remote 4 ALERT Low Limit register.
Remote ALERT
Low 4
Channel 3 Remote-Diode Low-Alert Bit. This bit is set to logic 1 when the channel 3
remote-diode temperature falls below the programmed temperature threshold limit in
the Remote 3 ALERT Low Limit register.
Remote ALERT
Low 3
Channel 2 Remote-Diode Low-Alert Bit. This bit is set to logic 1 when the channel 2
remote-diode temperature falls below the programmed temperature threshold limit in
the Remote 2 ALERT Low Limit register.
Remote ALERT
Low 2
Channel 1 Remote-Diode Low-Alert Bit. This bit is set to logic 1 when the channel 1
remote-diode temperature falls below the programmed temperature threshold limit in
the Remote 1 ALERT Low Limit register.
Remote ALERT
Low 1
of this pnp. If a sense transistor with an ideality factor
other than 1.008 is used, the output data is different
Effect of Ideality Factor
The accuracy of the remote temperature measurements
depends on the ideality factor (n) of the remote “diode”
(actually a transistor). The default value for the MAX6581
is n = 1.008 (channels 1–7). A thermal diode on the
substrate of an IC is normally a pnp with the base and
emitter brought out and the collector (diode connection)
grounded. DXP_ must be connected to the anode (emit-
ter) and DXN_ must be connected to the cathode (base)
from the data obtained with the optimum ideality factor. If
necessary, a different ideality factor value can be chosen
using the Transistor Ideality register (see Table 11). The
Ideality Select register allows each channel to have the
default ideality of 1.008 or the value programmed in the
Transistor Ideality register.
Analog Devices
│ 19
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Table 11. Transistor Ideality Register
IDEALITY
FACTOR
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
HEX
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
.999
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x0C
0x0D
0x0E
0x0F
0x10
0x11
0x12
0x13
0x14
0x15
0x16
0x17
0x18
0x19
0x1A
0x1B
0x1C
0x1D
0x1E
0x1F
1.000
1.001
1.002
1.003
1.004
1.005
1.006
1.007
1.008
1.009
1.010
1.011
1.012
1.013
1.014
1.015
1.016
1.017
1.018
1.019
1.020
1.021
1.022
1.023
1.024
1.025
1.026
1.027
1.028
1.029
1.030
0x4B
X = Don’t care.
Analog Devices
│ 20
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
interconnection resistance. Set these bits to 1 if the series
resistance is large enough to affect the accuracy of the
channels. The series-resistance cancellation function
increases the conversion time for the remote channels by
125ms (typ). This feature cancels the bulk resistance of
the sensor and any other resistance in series (e.g., wire,
contact resistance, etc.). The cancellation range is from
0Ω to 100Ω.
Series-Resistance Cancellation
Some thermal diodes on high-power ICs have exces-
sive series resistance that can cause temperature-mea-
surement errors when used with conventional remote-
temperature sensors. Channels 1–7 of the MAX6581
have a series-resistance cancellation feature (enabled
by bits [7:0] of the Resistance Cancellation register)
that eliminates the effect of diode series resistance and
Table 12. Resistance Cancellation Register (4Ah)
POR
STATE
BIT
7 (MSB)
6
NAME
FUNCTION
X
0
—
Resistance
Cancellation 7
Channel 7 Resistance Cancellation Enable Bit. Set this bit to logic 1 to enable
resistance cancellation. Set this bit to logic 0 to disable resistance cancellation.
0
0
0
0
0
0
0
Resistance
Cancellation 6
Channel 6 Resistance Cancellation Enable Bit. Set this bit to logic 1 to enable
resistance cancellation. Set this bit to logic 0 to disable resistance cancellation.
5
4
3
2
1
Resistance
Cancellation 5
Channel 5 Resistance Cancellation Enable Bit. Set this bit to logic 1 to enable
resistance cancellation. Set this bit to logic 0 to disable resistance cancellation.
Resistance
Cancellation 4
Channel 4 Resistance Cancellation Enable Bit. Set this bit to logic 1 to enable
resistance cancellation. Set this bit to logic 0 to disable resistance cancellation.
Resistance
Cancellation 3
Channel 3 Resistance Cancellation Enable Bit. Set this bit to logic 1 to enable
resistance cancellation. Set this bit to logic 0 to disable resistance cancellation.
Resistance
Cancellation 2
Channel 2 Resistance Cancellation Enable Bit. Set this bit to logic 1 to enable
resistance cancellation. Set this bit to logic 0 to disable resistance cancellation.
Resistance
Cancellation 1
Channel 1 Resistance Cancellation Enable Bit. Set this bit to logic 1 to enable
resistance cancellation. Set this bit to logic 0 to disable resistance cancellation.
0
X = Don’t care.
Analog Devices
│ 21
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
The Offset Enable register (4Eh) allows the offset to be
selectively enabled for each remote channel.
Offset and Offset Select Registers
(4Dh and 4Eh)
To compensate for remote temperature reporting errors
due to issues with the board layout, the Offset register
(4Dh) and Offset Enable register (4Eh) allow for a two’s-
complement value to be added to the final ADC conver-
sion output. The Offset register (4Dh) contains the value
for the shared temperature offset (i.e., the same offset is
applied to all selected remote channels) and has a pro-
grammable ±31.75°C range.
If EXTRANGE = 0, the minimum digital output values are
clamped at 00h (0°C), regardless of any applied offset.
If EXTRANGE = 1, the maximum digital output values
are clamped at FFh (+191°C), regardless of any applied
offset.
Table 13. Offset Register (4Dh)
POR
STATE
BIT
NAME
FUNCTION
7 (MSB)
SIGN
16°C
8°C
0
0
0
0
0
0
0
0
Digital Offset Polarity
6
5
4
3
2
1
0
Digital Offset (Weighted)
Digital Offset (Weighted)
Digital Offset (Weighted)
Digital Offset (Weighted)
Digital Offset (Weighted)
Digital Offset (Weighted)
Digital Offset (Weighted)
4°C
2°C
1°C
0.5°C
0.25°C
Table 14. Offset Select Register (4Eh)
POR
STATE
BIT
NAME
FUNCTION
7 (MSB)
X
0
0
0
0
0
0
0
0
—
6
5
4
3
2
1
0
Channel 7
Channel 6
Channel 5
Channel 4
Channel 3
Channel 2
Channel 1
Remote 7 Offset Enable
Remote 6 Offset Enable
Remote 5 Offset Enable
Remote 4 Offset Enable
Remote 3 Offset Enable
Remote 2 Offset Enable
Remote 1 Offset Enable
Analog Devices
│ 22
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
V
characteristics. Manufacturers of discrete transis-
BE
Applications Information
tors do not normally specify or guarantee ideality factor.
This normally is not a problem since good-quality discrete
transistors tend to have ideality factors that fall within a
relatively narrow range. Variations in remote temperature
readings of less than ±2°C with a variety of discrete tran-
sistors have been observed. However, it is good design
practice to verify good consistency of temperature read-
ings with several discrete transistors from any supplier
under consideration.
Remote-Diode Selection
The MAX6581 directly measures the die temperature of
CPUs and other ICs that have on-chip temperature-sensing
diodes (see the Typical Application Circuit), or it can measure
the temperature of a discrete diode-connected transistor.
Discrete Remote Diodes
When the remote-sensing diode is a discrete transistor,
its collector and base must be connected together. Table
13 lists examples of discrete transistors that are appropriate for
use with the MAX6581. The transistor must be a small-
Unused Diode Channels
If one or more of the remote-diode channels is not needed,
disconnect the DXP_ and DXN_ inputs for that channel, or
connect the DXP_ to the corresponding DXN_. The status
register indicates a diode “fault” for this channel and the
channel is ignored during the temperature-measurement
sequence. It is also good practice to mask any unused
channels immediately upon power-up by setting the appro-
priate bits in the ALERT Mask and OVERT Mask registers.
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 the 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 (e.g.,
50 < ß < 150) indicate that the manufacturer has good
process controls and that the devices have consistent
Table 15. Remote Sensors Transistor Suppliers (for Channels 1–7)
MODEL NO.
SUPPLIER
PNP
NPN
CMPT3906
2N3906
CMPT3904
Central Semiconductor Corp. (USA)
2N3904
2N3904
—
MMBT3906
2N3906
Fairchild Semiconductor (USA)
Infineon (Germany)
SMBT3906
MMBT3906
2N3906
ON Semiconductor (USA)
2N3904
ROHM Semiconductor (USA)
Samsung (Korea)
SST3906
SST3904
KST3906-TF
SMBT3906
KST3904-TF
SMBT3904
Siemens (Germany)
Zetex (England)
FMMT3906CT-ND
FMMT3904CT-ND
Note: Discrete transistors must be diode connected (base shorted to collector).
Analog Devices
│ 23
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Thermal Mass and Self-Heating
PCB Layout
When sensing local temperature, the MAX6581 measures
the temperature of the PCB to which it is soldered. The
leads provide a good thermal path between the PCB
traces and the die. As with all IC temperature sensors,
thermal conductivity between the die and the ambient air
is poor by comparison, making air-temperature measure-
ments impractical. Since the thermal mass of the PCB is
far greater than that of the MAX6581, the device follows
temperature changes on the PCB with little or no perceiv-
able 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
transistors, the best thermal-response times are obtained
with transistors in small packages (i.e., SOT23 or SC70).
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.
Follow the guidelines below to reduce the measurement
error when measuring remote temperature:
1) Place the MAX6581 as close as possible to
the remote diode. In noisy environments, such as a
computer motherboard, this distance is typically 4in
to 8in. This length can be increased if the worst-noise
sources are avoided. Noise sources include displays,
clock
generators, memory buses, and 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. Each parallel
pair of traces should go to a remote diode. Route
these traces away from any higher voltage traces,
such as +12V DC. Leakage currents from PCB
contamination must be dealt with carefully since a
20MΩ leakage path from DXP_ to ground causes
approximately +1°C error. If high-voltage traces are
unavoidable, connect guard traces to GND on either
side of the DXP_–DXN_ traces (Figure 5).
4) Route through as few vias and crossunders as
possible to minimize copper/solder thermocouple
effects.
ADC Noise Filtering
The integrating ADC has good noise rejection for
low-frequency signals, such as power-supply hum. In
environments with significant high-frequency EMI,
connect an external 100pF capacitor between DXP_ and
DXN_. Larger capacitor values can be used for added
filtering; however, it can introduce errors due to the rise
time of the switched current source. High-frequency noise
reduction is needed for high-accuracy remote measure-
ments. Noise can be reduced with careful PCB layout as
discussed in the PCB Layout section.
5) Use wide traces when possible (5-mil to 10-mil
traces are typical). Be aware of the effect of trace
resistance on temperature readings when using long,
narrow traces.
6) When the power supply is noisy, add a resistor
(up to 47Ω) in series with V
.
CC
GND
Slave Address
The slave address for the MAX6581 is shown in Table 16.
5–10 mils
MINIMUM
5–10 mils
5–10 mils
DXP_
DXN_
GND
Table 16. Slave Address
DEVICE ADDRESS
5–10 mils
A7
1
A6
0
A5
0
A4
1
A3
1
A2
0
A1
1
A0
R/W
R/W
R/W
R/W
1
0
0
1
1
1
0
1
0
0
1
1
1
1
1
0
0
1
1
0
0
Figure 5. Recommended DXP_–DXN_ PCB Traces. The two
outer guard traces are recommended if high-voltage traces are
near the DXN_ and DXP_ traces.
Analog Devices
│ 24
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
twisted-pair cables to DXP_ and DXN_ and the shielded
cable to GND. Leave the shielded cable unconnected at
the remote sensor. For very long cable runs, the cable’s
parasitic capacitance often provides noise filtering;
therefore the 100pF 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 +0.5°C.
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 such as those used for audio microphones. For
example, Belden #8451 works well for distances up to
100ft in a noisy environment. At the device, connect the
Typical Application Circuit
+3.3V
4.7kΩ
4.7kΩ 4.7kΩ
4.7kΩ
100pF
TO µP
TO µP
CPU
24
DXN1
23
DXP1
22
21
GND
20
19
N.C.
SMBCLK SMBDATA
1
18
17
16
15
14
13
DXP2
ALERT
TO µP
100pF
100pF
2
3
V
CC
DXN2
DXP3
0.1µF
OVERT
I.C.
TO µP
MAX6581
4
5
DXN3
DXP4
STBY
DXP7
6
N.C.
100pF
DXN4
DXP5
DXN5
9
DXN6
10
100pF
DXP6 DXN7
11 12
7
8
100pF
FPGA
ASIC
Analog Devices
│ 25
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.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.
24 TQFN-EP
T2444+4
21-0139
90-0022
Analog Devices
│ 26
www.analog.com
MAX6581
±1°C Accurate 8-Channel
Temperature Sensor
Revision History
REVISION REVISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
0
8/10
Initial release
—
Added the Package Thermal Characteristics section; updated Table 1; added 58h
register to Table 3; added the Offset and Offset Select Registers (4Dh and 4Eh)
section and related bit tables
2, 12, 14,
22
1
2/13
2
3
4
5
2/17
4/17
2/19
4/21
Updated Unused Diode Channels section
Updated Table 1
23
12
Updated OVERT Mask Register (43h) section, Table 6, and Table 8
Updated Ordering Information table and Table 16
15, 16, 18
1, 24
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is
assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that
may result from its use.Specifications subject to change without notice. No license is granted by implicationor
otherwise under any patent or patent rights of Analog Devices. Trademarks andregistered trademarks are the
property of their respective owners.
Analog Devices
│ 27
w w w . a n a l o g . c o m
相关型号：
MAX658CSD+
Switching Controller, Voltage-mode, 18kHz Switching Freq-Max, CMOS, PDSO14, 0.150 INCH, SO-14
MAXIM
MAX658ESD+
Switching Controller, Voltage-mode, 18kHz Switching Freq-Max, CMOS, PDSO14, 0.150 INCH, SO-14
MAXIM
©2020 ICPDF网 联系我们和版权申明