19-5260; Rev 4; 2/19
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 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).
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 -40°C to +125°C and is available in a 24-pin,
4mm x 4mm thin QFN package with an exposed pad.
Features
●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
●SMBus/I2C-Compatible Interface
●Two Open-Drain Alarm Outputs (ALERT and OVERT)
●Resistance Cancellation on All Remote Channels
Applications
●Desktop Computers
●Notebook Computers
●Workstations
●Servers
●Data Communications
Typical Application Circuit appears at end of data sheet.
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.
**Future product—contact factory for availability.
PART SLAVE ADDRESS PIN-PACKAGE OPERATING
TEMPERATURE RANGE
MEASURED
TEMPERATURE RANGE
MAX6581TG9A+ 0X9A 24 TQFN-EP* -40°C to +125°C -64°C to +150°C
MAX6581TG9C+** 0X9C 24 TQFN-EP* -40°C to +125°C -64°C to +150°C
MAX6581TG9E+** 0X9E 24 TQFN-EP* -40°C to +125°C -64°C to +150°C
MAX6581TG98+** 0X98 24 TQFN-EP* -40°C to +125°C -64°C to +150°C
Click here for production status of specic part numbers.
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
Ordering Information/Selector Guide
EVALUATION KIT AVAILABLE
(Note 1)
(All voltages referenced to GND.)
VCC, SMBCLK, SMBDATA, ALERT,
OVERT, STBY to GND ........................................ -0.3V to +4V
DXP_ to GND ........................................... -0.3V to (VCC + 0.3V)
DXN_ to GND ........................................... -0.3V to (VCC + 0.3V)
SMBDATA, ALERT, OVERT Current.................. -1mA to +50mA
DXN_ Current ..................................................................... ±1mA
Continuous Power Dissipation (TA = +70°C)
TQFN (derate 27.8mW/°C above +70°C)..................2222mW
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
TQFN
Junction-to-Ambient Thermal Resistance (θJA) ......36.0°C/W
Junction-to-Case Thermal Resistance (θJC) ..............3.0°C/W
(VCC = +3.0V to +3.6V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25°C.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage VCC 3.0 3.6 V
Standby Supply Current ISS SMBus static 4 15 µA
Operating Current ICC1 During conversion, RC o 500 600 µA
ICC2 During conversion, RC on 550 650
Temperature Resolution 11 Bits
0.125 °C
3-Sigma Temperature Accuracy
(Remote Channels 1–7) VCC = 3.3V
TA = +30°C to +85°C,
TRJ = +60°C to +100°C -0.85 +0.85
°CTA, TRJ = -40°C to +125°C -1.2 +1.2
TA = +30°C to +85°C,
TRJ = +100°C to +150°C -2.5 +2.5
3-Sigma Temperature Accuracy
(Local) VCC = 3.3V
TA = +30°C to +85°C -1 +1
°CTA = -40°C to +125°C -2 +2
TA = 0°C to +150°C -3 +3
6-Sigma Temperature Accuracy
(Remote Channels 1–7) VCC = 3.3V
TA = +30°C to +85°C,
TRJ = +60°C to +100°C -1 +1
°CTA, TRJ = -40°C to +125°C -2 +2
TA = +30°C to +85°C,
TRJ = +100°C to +125°C -2.75 +2.75
6-Sigma Temperature Accuracy
(Local) VCC = 3.3V
TA = +30°C to +85°C -1.5 +1.5
°CTA = -40°C to +125°C -2.5 +2.5
TA = 0°C to +150°C -3.5 +3.5
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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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.
Electrical Characteristics
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.
Package Thermal Characteristics
(VCC = +3.0V to +3.6V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25°C.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Sensitivity of Temperature
Accuracy ±0.2 °C/V
Conversion Time per Channel tCONV
Resistance cancellation mode o 95 125 156
ms
Resistance cancellation mode on or beta
compensation on 190 250 312
Remote-Diode Source Current IRJ
High level Resistance cancellation
mode o
80 100 120
µA
Low level 8 10 12
High level Resistance cancellation
mode on or beta
compensation on
160 200 240
Low level 16 20 24
DXP_ and DXN_ Leakage Current Standby mode 100 nA
Undervoltage Lockout Threshold UVLO Falling edge of VCC disables ADC 2.25 2.80 2.95 V
Undervoltage Lockout Hysteresis 90 mV
Power-On-Reset (POR)
Threshold VCC falling edge 1.3 2.0 2.2 V
POR Threshold Hysteresis 90 mV
ALERT and OVERT
Output Low Voltage VOL
ISINK = 1mA 0.01 V
ISINK = 6mA 0.3
Input Leakage Current ILEAK -1 +1 µA
SMBus INTERFACE, STBY
Logic Input Low Voltage VIL VCC = 3.6V 0.8 V
Logic Input High Voltage VIH VCC = 3.0V 2.2 V
Input Leakage Current -1 +1 µA
Output Low Voltage VOL ISINK = 6mA 0.1 V
Input Capacitance CIN 5 pF
SMBus-COMPATIBLE TIMING (Figures 3 and 4) (Note 3)
Serial-Clock Frequency fSMBCLK (Note 4) 400 kHz
Bus Free Time Between STOP
and START Condition tBUF fSMBCLK = 400kHz 1.6 µs
START Condition Setup Time fSMBCLK = 400kHz 0.6 µs
Repeated START Condition
Setup Time tSU:STA 90% of SMBCLK to 90% of SMBDATA,
fSMBCLK = 400kHz 50 ns
START Condition Hold Time tHD:STA
10% of SMBDATA to 90% of SMBCLK,
fSMBCLK = 400kHz 0.6 µs
STOP Condition Setup Time tSU:STO
90% of SMBCLK to 90% of SMBDATA,
fSMBCLK = 400kHz 0.6 µs
Clock Low Period tLOW 10% to 10%, fSMBCLK = 400kHz 1 µs
Clock High Period tHIGH 90% to 90% 0.6 µs
Data-In Hold Time tHD:DAT 0 0.9 µs
Data-In Setup Time tSU:DAT (Note 5) 100 ns
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Electrical Characteristics (continued)
(VCC = +3.0V to +3.6V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25°C.) (Note 2)
Note 2: All parameters are tested at TA = +85°C. Specifications over temperature are guaranteed by design.
Note 3: Timing specifications are guaranteed by design.
Note 4: The serial interface resets when SMBCLK is low for more than tTIMEOUT.
Note 5: A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SMBCLK’s falling
edge.
(VCC = +3.3V, VSTBY = VCC, TA = +25°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Receive SMBCLK/SMBDATA
Rise Time tR300 ns
Receive SMBCLK/SMBDATA Fall
Time tF300 ns
Data-Out Hold Time tDH 50 ns
Pulse Width of Spike Suppressed tSP 0 50 ns
SMBus Timeout tTIMEOUT SMBDATA low period for interface reset 25 37 45 ms
AVERAGE OPERATING SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6581 toc02
SUPPLY VOLTAGE (V)
AVERAGE OPERATING SUPPLY CURRENT (µA)
3.53.43.1 3.2 3.3
365
370
375
380
385
390
395
400
360
3.0 3.6
RESISTANCE
CANCELLATION OFF
REMOTE-DIODE TEMPERATURE ERROR
vs. REMODE-DIODE TEMPERATURE
MAX6581 toc03
REMOTE-DIODE TEMPERATURE (°C)
REMOTE-DIODE TEMPERATURE ERROR (°C)
1109050 703010
-3
-2
-1
0
1
2
3
4
5
6
7
8
9
10
-4
-5
-6
-7
-8
-9
-10 -10 130
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6581 toc01
SUPPLY VOLTAGE (V)
STANDBY SUPPLY CURRENT (µA)
3.53.43.33.23.1
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0
3.0 3.6
HARDWARE OR SOFTWARE
STANDBY SUPPLY CURRENT
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Electrical Characteristics (continued)
Typical Operating Characteristics
(VCC = +3.3V, VSTBY = VCC, TA = +25°C, unless otherwise noted.)
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX6581 toc04
DIE TEMPERATURE (°C)
LOCAL TEMPERATURE ERROR (°C)
908060 7010 20 30 40 500
-4
-3
-2
-1
0
1
2
3
4
5
-5
-10 100
REMOTE-DIODE TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6581 toc05
POWER-SUPPLY NOISE FREQUENCY (MHz)
REMOTE-DIODE TEMPERATURE ERROR (°C)
10.10.01
-4
-3
-2
-1
0
1
2
3
4
5
-5
0.001 10
100mVP-P
TRJ = +85°C
LOCAL TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6581 toc06
POWER-SUPPLY NOISE FREQUENCY (MHz)
LOCAL TEMPERATURE ERROR (°C)
10.10.01
-4
-3
-2
-1
0
1
2
3
4
5
-5
0.001 10
100mVP-P
REMOTE-DIODE TEMPERATURE ERROR
vs. CAPACITANCE
MAX6581 toc07
CAPACITANCE (nF)
REMOTE-DIODE TEMPERATURE ERROR (°C)
10
-4
-3
-2
-1
0
1
2
3
4
5
-5
1 100
100mVP-P
TRJ = +85°C
REMOTE-DIODE TEMPERATURE ERROR
vs. RESISTANCE
MAX6581 toc08
RESISTANCE (Ω)
REMOTE-DIODE TEMPERATURE ERROR (°C)
908060 7020 30 40 5010
0
5
10
15
20
25
30
35
40
45
50
-5
0 100
TRJ = +85°C
RESISTANCE
CANCELLATION OFF
RESISTANCE
CANCELLATION ON
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
Maxim Integrated
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Typical Operating Characteristics (continued)
PIN NAME FUNCTION
1 DXP2
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 ltering.
2 DXN2
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 ltering.
3 DXP3
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 ltering.
4 DXN3
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 ltering.
5 DXP4
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 ltering.
6, 22 N.C. No Connection. Connect to other N.C. or leave unconnected.
23
24
22
21
8
7
9
DXN2
DXN3
DXP4
N.C.
10
DXP2
VCC
I.C.
STBY
ALERT
DXP7
1 2
N.C.
4 5 6
1718 16 14 13
DXP1
DXN1
DXN6
DXN5
DXP5
DXN4
MAX6581
DXP3 OVERT
3
15
GND
20 11 DXP6
SMBCLK
19 12 DXN7
SMBDATA
TOP VIEW
*EP = EXPOSED PAD, CONNECT TO GND
*EP
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Pin Description
Pin Conguration
PIN NAME FUNCTION
7 DXN4
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 ltering.
8 DXP5
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 ltering.
9 DXN5
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 ltering.
10 DXN6
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 ltering.
11 DXP6
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 ltering.
12 DXN7
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 ltering.
13 DXP7
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 ltering.
14 STBY 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.
15 I.C. Internally Connected. I.C. is internally connected to VCC. Connect I.C. to VCC or leave unconnected.
16 OVERT Overtemperature Active-Low, Open-Drain Output. OVERT asserts low when the temperature of any
remote channel exceeds the programmed threshold limit.
17 VCC Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.
18 ALERT 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.
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.
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Pin Description (continued)
Detailed Description
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.
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 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
interface is inactive. During software standby, the SMBus
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.
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:
NR
AV CC1 CC2
NR NR
N 1 2N
II I
N 2N 1 N 2N 1
+×
= +×
+× + +× +
where:
NN = the number of remote channels that are operating
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.
ICC1 = the average operating power-supply current
during a conversion in normal mode.
ICC2 = the average operating power-supply current
during a conversion in RC mode.
PIN NAME FUNCTION
21 GND Ground
23 DXP1
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 ltering.
24 DXN1
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 ltering.
— EP Exposed Pad. Connect EP to GND.
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Pin Description (continued)
Figure 1. Internal Block Diagram
VCC
DXN2
DXP2
DXN1
DXP1
DXN3
DXP3
DXN4
DXP4
DXN5
DXP5
DXN6
DXP6
LOCAL
TRANSISTOR
SMBCLK SMBDATA
INPUT
BUFFER
REF
COUNTER
SMBus INTERFACE
COUNT
+
-
DXN7
DXP7
IRJ
REGISTER BANK
COMMAND BYTE
REMOTE TEMPERATURES
LOCAL TEMPERATURES
STBY
OVERT
ALERT THRESHOLD
OVERT THRESHOLD
ALERT RESPONSE ADDRESS
ALERT
ALARM
ALU
MAX6581
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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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 MAX6581 employs four standard SMBus protocols:
write byte, read byte, send byte, and receive byte (Figure 2).
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-
ing the first master. Figure 3 is the SMBus write timing
diagram and Figure 4 is the SMBus read timing diagram.
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.
Figure 2. SMBus Protocols
S ADDRESS WR ACK ACK PDATA ACKCOMMAND
7 BITS 18 BITS8 BITS
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)
WRITE-BYTE FORMAT
S ADDRESSADDRESS WR ACK ACK PS RD ACK ///DATACOMMAND
7 BITS 7 BITS 8 BITS8 BITS
READ-BYTE FORMAT
SLAVE ADDRESS: EQUIVALENT
TO CHIP SELECT LINE
COMMAND BYTE: SELECTS
WHICH REGISTER YOU ARE
READING FROM
S PADDRESS WR ACK ACKCOMMAND
7 BITS 8 BITS
SEND-BYTE FORMAT
COMMAND BYTE: SENDS COMMAND
WITH NO DATA, USUALLY
USED FOR ONE-SHOT COMMAND
S PADDRESS RD ACK ///DATA
7 BITS 8 BITS
RECEIVE-BYTE FORMAT
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
SLAVE ADDRESS: REPEATED
DUE TO CHANGE IN DATA-
FLOW DIRECTION
DATA BYTE: READS FROM
THE REGISTER SET BY THE
COMMAND BYTE
S = START CONDITION
P = STOP CONDITION
SHADED = SLAVE TRANSMISSION
/// = NOT ACKNOWLEDGED
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Figure 3. SMBus Write Timing Diagram
Figure 4. Read-Timing Diagram
SMBCLK
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
A B C D EF G H I J
SMBDATA
tSU:STA tHD:STA
tLOW tHIGH
tSU:DAT tSU:STO tBUF
L MK
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
SMBCLK
A B C D EF G H I
SMBDATA
tSU:STA tHD:STA
tLOW tHIGH
tSU:DAT tHD:DAT tSU:STO tBUF
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
JK
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
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Table 1. Main Temperature Register (High-Byte) Data Format
Table 2. Extended-Resolution Temperature Register (Low-Byte) Data Format
X = Don’t care.
TEMPERATURE (°C)
DIGITAL OUTPUT
NORMAL FORMAT
EXTRANGE = 0
EXTENDED FORMAT
EXTRANGE = 1
Diode fault (open or short) 1111 1111 1111 1111
> +254 1111 1111 1111 1111
+254 1111 1110 1111 1111
+191 1011 1111 1111 1111
+190 1011 1110 1111 1110
+125 0111 1101 1011 1101
+85 0101 0101 1001 0101
+25 0001 1001 0101 1001
0 0000 0000 0100 0000
-1 0000 0000 0011 1111
-40 0000 0000 0001 1000
-63 0000 0000 0000 0001
-64 0000 0000 0000 0000
< -64 0000 0000 0000 0000
TEMPERATURE (°C) DIGITAL OUTPUT
0 000X XXXX
+0.125 001X XXXX
+0.250 010X XXXX
+0.375 011X XXXX
+0.500 100X XXXX
+0.625 101X XXXX
+0.750 110X XXXX
+0.875 111X XXXX
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Table 3. Command Byte Register Bit Assignment
REGISTER ADDRESS
(HEX)
POR
VALUE
(HEX)
READ/
WRITE DESCRIPTION
Remote 1 01 00 R Read channel 1 remote temperature
Remote 2 02 00 R Read channel 2 remote temperature
Remote 3 03 00 R Read channel 3 remote temperature
Remote 4 04 00 R Read channel 4 remote temperature
Remote 5 05 00 R Read channel 5 remote temperature
Remote 6 06 00 R Read channel 6 remote temperature
Local 07 00 R Read local temperature
Remote 7 08 00 R Read channel 7 remote temperature
Remote 1 Extended
Bits* 09 00 R Read channel 1 remote-diode extended temperature
Manufacturer ID 0A 4D R Read manufacturer ID
Revision ID 0F 00 R Read revision ID
Remote 1 ALERT High
Limit 11 7F R/W Read/write channel 1 remote-diode alert high-temperature
threshold limit
Remote 2 ALERT High
Limit 12 7F R/W Read/write channel 2 remote-diode alert high-temperature
threshold limit
Remote 3 ALERT High
Limit 13 64 R/W Read/write channel 3 remote-diode alert high-temperature
threshold limit
Remote 4 ALERT High
Limit 14 64 R/W Read/write channel 4 remote-diode alert high-temperature
threshold limit
Remote 5 ALERT High
Limit 15 64 R/W Read/write channel 5 remote-diode alert high-temperature
threshold limit
Remote 6 ALERT High
Limit 16 64 R/W Read/write channel 6 remote-diode alert high-temperature
threshold limit
Local ALERT High Limit 17 5A R/W Read/write local-diode alert high-temperature threshold limit
Remote 7 ALERT High
Limit 18 64 R/W Read/write channel 7 remote-diode alert high-temperature
threshold limit
Local OVERT High Limit 20 50 R/W Read/write channel local-diode overtemperature threshold limit
Remote 1 OVERT High
Limit 21 6E R/W Read/write channel 1 remote-diode overtemperature threshold limit
Remote 2 OVERT High
Limit 22 6E R/W Read/write channel 2 remote-diode overtemperature threshold limit
Remote 3 OVERT High
Limit 23 6E R/W Read/write channel 3 remote-diode overtemperature threshold limit
Remote 4 OVERT High
Limit 24 7F R/W Read/write channel 4 remote-diode overtemperature threshold limit
Remote 5 OVERT High
Limit 25 5A R/W Read/write channel 5 remote-diode overtemperature threshold limit
Remote 6 OVERT High
Limit 26 5A R/W Read/write channel 6 remote-diode overtemperature threshold limit
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Table 3. Command Byte Register Bit Assignment (continued)
*Duplicate entries.
REGISTER ADDRESS
(HEX)
POR
VALUE
(HEX)
READ/
WRITE DESCRIPTION
Remote 7 OVERT High
Limit 27 5A R/W Read/write channel 7 remote-diode overtemperature threshold limit
ALERT Low Limits (all
channels) 30 00 R/W Read/write all channels alert low-temperature threshold limit
Conguration 41 00 R/W Read/write conguration
ALERT Mask 42 00 R/W Read/write ALERT mask
OVERT Mask 43 00 R/W Read/write OVERT mask
ALERT High Status 44 00 R Read ALERT high status
OVERT Status 45 00 R Read OVERT status
Diode Fault Status 46 00 R Read diode fault status
ALERT Low Status 47 00 R Read ALERT low status
ALERT Low Disable 48 FF R/W Read/write ALERT low disable
Resistance Cancellation 4A 00 R/W Read/write resistance cancellation enable bits (1 = On, 0 = O)
Transistor Ideality 4B 00 R/W Read/write ideality value for remote-sense transistor
Ideality Select 4C 00 R/W Read/write ideality value selection bits (1 = selected transistor
ideality, 0 = 1.008)
Oset 4D 00 R/W Read/write temperature oset value
Oset Select 4E 00 R/W Read/write oset value selection bits (1 = value in Oset register,
0 = 0)
Remote 1 Extended
Bits* 51 00 R Read channel 1 remote extended temperature
Remote 2 Extended Bits 52 00 R Read channel 2 remote extended temperature
Remote 3 Extended Bits 53 00 R Read channel 3 remote extended temperature
Remote 4 Extended Bits 54 00 R Read channel 4 remote extended temperature
Remote 5 Extended Bits 55 00 R Read channel 5 remote extended temperature
Remote 6 Extended Bits 56 00 R Read channel 6 remote extended temperature
Local Extended Bits 57 00 R Read local channel extended temperature
Remote 7 Extended Bits 58 00 R Read channel 7 remote extended temperature
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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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.
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.
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.
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.
The alert response can activate several different slave
devices simultaneously, similar to the I2C general call. If
more than one slave attempts to respond, bus arbitration
rules apply, and the device with the lower address code
wins. The losing device does not generate an 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.
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.
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).
Conguration 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).
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).
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Table 4. Configuration Register (41h)
Table 5. ALERT Mask Register (42h)
Table 6. OVERT Mask Register (43h)
BIT NAME POR
VALUE FUNCTION
7 (MSB) STOP 0 Standby-Mode Control Bit. If STOP is set to logic 1, the MAX6581 stops converting and
enters standby mode.
6 POR 0 Reset Bit. Set to logic 1 to put the device into its power-on state. This bit is self-clearing.
5TIMEOUT 0 Timeout Enable Bit. Set to logic 0 to enable SMBus timeout.
4 RESERVED 0 Reserved. Must be set to 0.
3 RESERVED 0 Reserved. Must be set to 0.
2 RESERVED 0 Reserved. Must be set to 0.
1 EXTRANGE 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.
0 RESERVED 0 Reserved. Must be set to 0.
BIT NAME POR
VALUE FUNCTION
7 (MSB) Mask ALERT 7 0 Channel 7 Alert Mask. Set to logic 1 to mask channel 7 ALERT.
6Mask Local
ALERT 0 Local Alert Mask. Set to logic 1 to mask local channel ALERT.
5 Mask ALERT 6 0 Channel 6 Alert Mask. Set to logic 1 to mask channel 6 ALERT.
4 Mask ALERT 5 0 Channel 5 Alert Mask. Set to logic 1 to mask channel 5 ALERT.
3 Mask ALERT 4 0 Channel 4 Alert Mask. Set to logic 1 to mask channel 4 ALERT.
2 Mask ALERT 3 0 Channel 3 Alert Mask. Set to logic 1 to mask channel 3 ALERT.
1 Mask ALERT 2 0 Channel 2 Alert Mask. Set to logic 1 to mask channel 2 ALERT.
0 Mask ALERT 1 0 Channel 1 Alert Mask. Set to logic 1 to mask channel 1 ALERT.
BIT NAME POR
VALUE FUNCTION
7 (MSB) Mask Local
OVERT 0 Local Overt Mask. Set to logic 1 to mask local channel OVERT.
6 Mask OVERT 7 0 Channel 7 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 7 OVERT.
5 Mask OVERT 6 0 Channel 6 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 6 OVERT.
4 Mask OVERT 5 0 Channel 5 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 5 OVERT.
3 Mask OVERT 4 0 Channel 4 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 4 OVERT.
2 Mask OVERT 3 0 Channel 3 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 3 OVERT.
1 Mask OVERT 2 0 Channel 2 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 2 OVERT.
0 Mask OVERT 1 0 Channel 1 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 1 OVERT.
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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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.
Bits in the alert status registers are cleared by a success-
ful read, but set again after the next conversion unless
the fault is corrected, either by a drop in the measured
temperature or a change in the threshold temperature.
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.
Table 7. ALERT High Status Register (44h)
BIT NAME POR
STATE FUNCTION
7 (MSB) Remote ALERT
High 7 0
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.
6Local ALERT
High 0Local 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.
5Remote ALERT
High 6 0
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.
4Remote ALERT
High 5 0
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.
3Remote ALERT
High 4 0
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.
2Remote ALERT
High 3 0
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.
1Remote ALERT
High 2 0
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.
0Remote ALERT
High 1 0
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.
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Table 8. OVERT Status Register (45h)
Table 9. Diode Fault Status Register (46h)
BIT NAME POR
STATE FUNCTION
7 (MSB) Local OVERT 0
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.
6 Remote OVERT 7 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.
5 Remote OVERT 6 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.
4 Remote OVERT 5 0
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.
3 Remote OVERT 4 0
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.
2 Remote OVERT 3 0
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.
1 Remote OVERT 2 0
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.
0 Remote OVERT 1 0
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.
BIT NAME POR
STATE FUNCTION
7 (MSB) RESERVED 0 —
6 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 VCC.
5 Diode Fault 6 0 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 VCC.
4 Diode Fault 5 0 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 VCC.
3 Diode Fault 4 0 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 VCC.
2 Diode Fault 3 0 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 VCC.
1 Diode Fault 2 0 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 VCC.
0 Diode Fault 1 0 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 VCC.
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Eect 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)
of this pnp. If a sense transistor with an ideality factor
other than 1.008 is used, the output data is different
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.
Table 10. ALERT Low Status Register (47h)
BIT NAME POR
STATE FUNCTION
7 (MSB) Remote ALERT
Low 7 0
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.
6 Local ALERT Low 0
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.
5Remote ALERT
Low 6 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.
4Remote ALERT
Low 5 0
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.
3Remote ALERT
Low 4 0
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.
2Remote ALERT
Low 3 0
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.
1Remote ALERT
Low 2 0
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.
0Remote ALERT
Low 1 0
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.
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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Table 11. Transistor Ideality Register
X = Don’t care.
REGISTER B7 B6 B5 B4 B3 B2 B1 B0 IDEALITY
FACTOR HEX
0x4B
X X X 0 0 0 0 0 .999 0x00
X X X 0 0 0 0 1 1.000 0x01
X X X 0 0 0 1 0 1.001 0x02
X X X 0 0 0 1 1 1.002 0x03
X X X 0 0 1 0 0 1.003 0x04
X X X 0 0 1 0 1 1.004 0x05
X X X 0 0 1 1 0 1.005 0x06
X X X 0 0 1 1 1 1.006 0x07
X X X 0 1 0 0 0 1.007 0x08
X X X 0 1 0 0 1 1.008 0x09
X X X 0 1 0 1 0 1.009 0x0A
X X X 0 1 0 1 1 1.010 0x0B
X X X 0 1 1 0 0 1.011 0x0C
X X X 0 1 1 0 1 1.012 0x0D
X X X 0 1 1 1 0 1.013 0x0E
X X X 0 1 1 1 1 1.014 0x0F
X X X 1 0 0 0 0 1.015 0x10
X X X 1 0 0 0 1 1.016 0x11
X X X 1 0 0 1 0 1.017 0x12
X X X 1 0 0 1 1 1.018 0x13
X X X 1 0 1 0 0 1.019 0x14
X X X 1 0 1 0 1 1.020 0x15
X X X 1 0 1 1 0 1.021 0x16
X X X 1 0 1 1 1 1.022 0x17
X X X 1 1 0 0 0 1.023 0x18
X X X 1 1 0 0 1 1.024 0x19
X X X 1 1 0 1 0 1.025 0x1A
X X X 1 1 0 1 1 1.026 0x1B
X X X 1 1 1 0 0 1.027 0x1C
X X X 1 1 1 0 1 1.028 0x1D
X X X 1 1 1 1 0 1.029 0x1E
X X X 1 1 1 1 1 1.030 0x1F
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor
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