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MAX6642
±1°C, SMBus-Compatible Remote/
Local Temperature Sensor with
Overtemperature Alarm
General Description
The MAX6642 precise, two-channel digital temperature
sensor accurately measures the temperature of its own
die and a remote PN junction and reports the temperature
data over a 2-wire serial interface. The remote PN junction
is typically a substrate PNP transistor on the die of a CPU,
ASIC, GPU, or FPGA. The remote PN junction can also be
a discrete diode-connected small-signal transistor.
The 2-wire serial interface accepts standard system
management bus (SMBus™), Write Byte, Read Byte,
Send Byte, and Receive Byte commands to read the
temperature data and to program the alarm thresholds.
To enhance system reliability, the MAX6642 includes
an SMBus timeout. The temperature data format is 10
bit with the least significant bit (LSB) corresponding to
+0.25°C. The ALERT output asserts when the local or
remote overtemperature thresholds are violated. A fault
queue may be used to prevent the ALERT output from
setting until two consecutive faults have been detected.
Benefits and Features
● Integrated Temperature Sensor Enables Simultaneous
Dual Temperature (Remote and Local) Measurements
• Remote Accuracy ±1°C
• Local Accuracy ±2°C from +60°C to +100°C
• Measures Remote Temperature up to +150°C
• 0.25°C Resolution
● Dual Zone Monitoring Automates Over-Temperature
Alarms
• Programmable Remote/Local Temperature
Thresholds
• ALERT Output
● Small Footprint
• 3mm x 3mm TDFN Package with Exposed Pad
• Low Thermal Mass Reduces Measurement Latency
• SMBus/I2C Address Hardwired
Ordering Information
PART
TEMP RANGE
MAX6642ATT90-T
-40°C to +125°C
6 TDFN-EP*
Remote accuracy is ±1°C maximum error between +60°C
and +100°C. The MAX6642 operates from -40°C to
+125°C, and measures remote temperatures between
0°C and +150°C. The MAX6642 is available in a 6-pin
TDFN package with an exposed pad.
MAX6642ATT92-T
-40°C to +125°C
6 TDFN-EP*
MAX6642ATT94-T
-40°C to +125°C
6 TDFN-EP*
MAX6642ATT96-T
-40°C to +125°C
6 TDFN-EP*
MAX6642ATT98-T
-40°C to +125°C
6 TDFN-EP*
MAX6642ATT9A-T
-40°C to +125°C
6 TDFN-EP*
Applications
MAX6642ATT9C-T
-40°C to +125°C
6 TDFN-EP*
MAX6642ATT9E-T
T = Tape and reel.
*EP = Exposed pad.
-40°C to +125°C
6 TDFN-EP*
Measurements can be done autonomously or in a singleshot mode.
●
●
●
●
Desktop Computers
Notebook Computers
Servers
Thin Clients
● Test and Measurement
● Workstations
● Graphic Cards
Selector Guide
Pin Configuration and Functional Diagram appear at end of
data sheet.
Typical Operating Circuit
MEASURED TEMP RANGE
TOP
MARK
MAX6642ATT90-T
0°C to +150°C
AFC
MAX6642ATT92-T
0°C to +150°C
AFD
MAX6642ATT94-T
0°C to +150°C
AFE
MAX6642ATT96-T
0°C to +150°C
AFF
MAX6642ATT98-T
0°C to +150°C
AEW
MAX6642ATT9A-T
0°C to +150°C
AFG
MAX6642ATT9C-T
0°C to +150°C
AFH
MAX6642ATT9E-T
0°C to +150°C
AFI
PART
PIN-PACKAGE
0.1µF
3.3V
47Ω
10kΩ EACH
VCC
2200pF
MAX6642
SDA
DXP
SCLK
µP
GND
ALERT
DATA
CLOCK
INTERRUPT TO µP
19-2920; Rev 6; 5/22
SMBus is a trademark of Intel Corp.
© 2022 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
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© 2022 Analog Devices, Inc. All rights reserved.
MAX6642
±1°C, SMBus-Compatible Remote/
Local Temperature Sensor with
Overtemperature Alarm
Absolute Maximum Ratings
All Voltages Referenced to GND
VCC...........................................................................-0.3V to +6V
DXP........................................................... -0.3V to (VCC + 0.3V)
SCLK, SDA, ALERT.................................................-0.3V to +6V
SDA, ALERT Current.......................................... -1mA to +50mA
Continuous Power Dissipation (TA = +70°C)
6-Pin TDFN (derate 24.4mW/°C above +70°C) .........1951mW
ESD Protection (all pins, Human Body Model)................±2000V
Junction Temperature.......................................................+150°C
Operating Temperature Range.......................... -40°C to +125°C
Storage Temperature Range............................. -65°C to +150°C
Lead Temperature (soldering, 10s).................................. +300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Electrical Characteristics
(VCC = +3.0V to +5.5V, TA = -40°C to +125°C, unless otherwise specified. Typical values are at VCC = +3.3V and TA = +25°C.) (Note 1)
PARAMETER
Supply Voltage
SYMBOL
CONDITIONS
VCC
MIN
3.0
Temperature Resolution
Remote Temperature Error
VCC = 3.3V
Local Temperature Error
VCC = 3.3V
UNITS
5.5
V
0.25
°C
10
Bits
-1.0
+1.0
TRJ = 0°C to +125°C
-3.0
+3.0
TRJ = +125°C to +150°C
-3.5
+3.5
TA = +60°C to +100°C
-2.0
+2.0
TA = 0°C to +125°C
-3.0
+3.0
±0.2
UVLO
Falling edge of VCC disables ADC
2.4
Undervoltage Lockout Hysteresis
2.7
VCC falling edge
1.5
POR Threshold Hysteresis
2.0
2.95
SMBus static
Operating Current
During conversion
Average Operating Current
2.4
tCONV
Conversion Rate
fCONV
IRJ
From stop bit to conversion completion
106
V
V
mV
3
10
µA
0.5
1.0
mA
260
Conversion Time
°C
mV
90
Standby Supply Current
°C
°C/V
90
Power-On-Reset (POR) Threshold
Remote-Diode Source Current
MAX
TRJ = +60°C to +100°C,
TA = +25°C to +85°C
Supply Sensitivity of
Temperature Error
Undervoltage Lockout Threshold
TYP
125
µA
143
8
ms
Hz
High level
80
100
120
Low level
8
10
12
VOL = 0.4V
1
VOL = 0.6V
4
µA
ALERT
Output-Low Sink Current
Output-High Leakage Current
www.analog.com
VOH = VCC
mA
1
µA
Analog Devices │ 2
MAX6642
±1°C, SMBus-Compatible Remote/
Local Temperature Sensor with
Overtemperature Alarm
Electrical Characteristics (continued)
(VCC = +3.0V to +5.5V, TA = -40°C to +125°C, unless otherwise specified. Typical values are at VCC = +3.3V and TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
0.8
V
SMBus-COMPATIBLE INTERFACE (SCLK and SDA)
Logic Input Low Voltage
VIL
Logic Input High Voltage
VIH
Input Leakage Current
ILEAK
Output Low Sink Current
IOL
Input Capacitance
CIN
VCC = 3.0V
2.2
VIN = GND or 5.5V
-1
VOL = 0.6V
6
V
+1
µA
mA
5
pF
SMBus TIMING (Note 2)
Serial Clock Frequency
fSCLK
Bus Free Time Between STOP
and START Condition
tBUF
(Note 3)
START Condition Setup Time
100
kHz
4.7
µs
4.7
µs
Repeat START Condition Setup
Time
tSU:STA
90% to 90%
50
ns
START Condition Hold Time
tHD:STA
10% of SDA to 90% of SCLK
4
µs
STOP Condition Setup Time
tSU:STO
90% of SCLK to 90% of SDA
4
µs
Clock Low Period
tLOW
10% to 10%
4.7
µs
Clock High Period
tHIGH
90% to 90%
4
µs
Data Setup Time
tHD:DAT
(Note 4)
250
ns
Receive SCLK/SDA Rise Time
tR
1
µs
Receive SCLK/SDA Fall Time
tF
300
ns
50
ns
40
ms
Pulse Width of Spike
Suppressed
SMBus Timeout
Note
Note
Note
Note
1:
2:
3:
4:
tSP
tTIMEOUT
0
SDA low period for interface reset
20
28
All parameters tested at TA = +25°C. Specifications over temperature are guaranteed by design.
Timing specifications guaranteed by design.
The serial interface resets when SCLK is low for more than tTIMEOUT.
A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SCLK’s falling edge.
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Analog Devices │ 3
MAX6642
±1°C, SMBus-Compatible Remote/
Local Temperature Sensor with
Overtemperature Alarm
Typical Operating Characteristics
(VCC = 3.3V, TA = +25°C, unless otherwise noted.)
STANDBY SUPPLY CURRENT
vs. CLOCK FREQUENCY
4.0
3.5
3.0
2.5
2.0
1.5
0.1
1
10
100
25
75
100
MAX6642 toc02
1.5
100
125
REMOTE ERROR
1.0
LOCAL ERROR
0.5
0
-0.5
VIN = 100mVP-P SQUARE WAVE
APPLIED TO VCC WITH NO BYPASS CAPACITOR
-1.5
0.0001 0.001
125
0.01
0.1
1
10
TEMPERATURE (°C)
FREQUENCY (kHz)
TEMPERATURE ERROR
vs. DXP NOISE FREQUENCY
TEMPERATURE ERROR
vs. DXP-GND CAPACITANCE
MAX6642 toc05
TEMPERATURE ERROR (°C)
50
VIN = AC-COUPLED TO DXP
VIN = 100mVP-P SQUARE WAVE
70
REMOTE ERROR
60
50
40
LOCAL ERROR
20
2.0
100
1.0
0
-1.0
-2.0
-3.0
-4.0
-5.0
10
0.01
0.1
1
FREQUENCY (kHz)
www.analog.com
75
2.0
-1.0
0
0.001
50
MAX6642 toc04
MAX 6642 toc03
TEMPERATURE ERROR (°C)
-2
100
25
TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
-1
0
0
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
0
30
-3
TEMPERATURE (°C)
1
80
-2
CLOCK FREQUENCY (kHz)
TEMPERATURE ERROR (°C)
0.01
2
90
-1
2N3906
3
-3
0
-4
TEMPERATURE ERROR (°C)
1.0
1
MAX6642 toc06
SUPPLY CURRENT (µA)
4.5
2
TEMPERATURE ERROR (°C)
MAX6642 toc01
5.0
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
10
100
-6.0
0.1
1
10
100
DXP-GND CAPACITANCE (nF)
Analog Devices │ 4
MAX6642
±1°C, SMBus-Compatible Remote/
Local Temperature Sensor with
Overtemperature Alarm
Pin Description
PIN
NAME
FUNCTION
1
VCC
Supply Voltage Input, +3V to +5.5V. Bypass VCC to GND with a 0.1µF capacitor.
A 47Ω series resistor is recommended but not required for additional noise filtering.
2
GND
Ground
3
DXP
Combined Remote-Diode Current Source and ADC Input for Remote-Diode Channel.
Place a 2200pF capacitor between DXP and GND for noise filtering.
4
SCLK
SMBus Serial-Clock Input. May be pulled up to +5.5V regardless of VCC.
5
SDA
6
ALERT
—
EP
SMBus Serial-Data Input/Output, Open Drain. May be pulled up to +5.5V regardless of VCC.
SMBus Alert (Interrupt) Output, Open Drain. ALERT asserts when temperature exceeds user-set limits.
See the ALERT Interrupts section.
Exposed Pad. Internally connected to GND. Connect to a PCB ground pad for optimal performance.
Not intended as an electrical connection point.
Detailed Description
The MAX6642 is a temperature sensor for local and remote
temperature-monitoring applications. Communication with
the MAX6642 occurs through the SMBus-compatible
serial interface and dedicated alert pins. ALERT asserts if
the measured local or remote temperature is greater than
the software-programmed ALERT limit.
The MAX6642 converts temperatures to digital data either
at a programmed rate of eight conversions per second or
in single conversions. Temperature data is represented
by 8 data bits (at addresses 00h and 01h), with the
LSB equal to +1°C and the MSB equal to +128°C. Two
additional bits of remote temperature data are available in
the “extended” register at address 10h and 11h (Table 2)
providing resolution of +0.25°C.
ADC and Multiplexer
The averaging ADC integrates over a 60ms period (each
channel, typ), with excellent noise rejection.
The multiplexer automatically steers bias currents through
the remote and local diodes. The ADC and associated circuitry measure each diode’s forward voltage and compute
the temperature based on this voltage. Both channels are
automatically converted once the conversion process has
started, either in free-running or single-shot mode. If one of
the two channels is not used, the device still performs both
measurements, and the user can ignore the results of the
unused channel. If the remote-diode channel is unused,
connect DXP to GND rather than leaving DXP open.
The conversion time per channel (remote and internal)
is 125ms. If both channels are being used, then each
channel is converted four times per second. If the external conversion-only option is selected, then the remote
temperature is measured eight times per second.
www.analog.com
The results of the previous conversion are always available, even if the ADC is busy.
Low-Power Standby Mode
Standby mode reduces the supply current to less than
10μA by disabling the ADC and timing circuitry. Enter
standby mode by setting the RUN bit to 1 in the configuration byte register (Table 4). All data is retained in memory,
and the SMBus interface is active and listening for SMBus
commands. Standby mode is not a shutdown mode. With
activity on the SMBus, the device draws more supply current (see the Typical Operating Characteristics). In standby mode, the MAX6642 can be forced to perform ADC
conversions through the one-shot command, regardless
of the RUN bit status.
If a standby command is received while a conversion is in
progress, the conversion cycle is truncated, and the data
from that conversion is not latched into a temperature
register. The previous data is not changed and remains
available.
Supply-current drain during the 125ms conversion period
is 500μA (typ). In standby mode, supply current drops to
3μA (typ).
SMBus Digital Interface
From a software perspective, the MAX6642 appears
as a set of byte-wide registers that contain temperature
data, alarm threshold values, and control bits. A standard
SMBus-compatible 2-wire serial interface is used to read
temperature data and write control bits and alarm threshold data.
The MAX6642 employs four standard SMBus protocols:
Write Byte, Read Byte, Send Byte, and Receive Byte.
(Figures 1, 2, and 3). The shorter Receive Byte protocol
allows quicker transfers, provided that the correct data
Analog Devices │ 5
MAX6642
±1°C, SMBus-Compatible Remote/
Local Temperature Sensor with
Overtemperature Alarm
WRITE BYTE FORMAT
S
ADDRESS
WR
ACK
COMMAND
7 BITS
ACK
DATA
8 BITS
ACK
P
8 BITS
SLAVE ADDRESS: EQUIVALENT TO CHIP-SELECT LINE OF
A 3-WIRE INTERFACE
1
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
7 BITS
ACK
S
SLAVE ADDRESS: EQUIVALENT TO CHIP SELECT LINE
ADDRESS
RD
ACK
DATA
7 BITS
COMMAND BYTE: SELECTS
WHICH REGISTER YOU ARE
REDING FROM
///
P
8 BITS
SLAVE ADDRESS: REPEATED
DUE TO CHANGE IN DATAFLOW DIRECTION
SEND BYTE FORMAT
S
ADDRESS
8 BITS
DATA BYTE: READS FROM
THE REGISTER SET BY THE
COMMAND BYTE
RECEIVE BYTE FORMAT
WR
ACK
COMMAND
7 BITS
ACK
P
S
ADDRESS
8 BITS
RD
ACK
DATA
7 BITS
COMMAND BYTE: SENDS COMMAND WITH NO DATA, USUALLY
USED FOR ONE-SHOT COMMAND
S = START CONDITION
P = STOP CONDITION
///
P
8 BITS
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
SHADED = SLAVE TRANSMISSION
/// = NOT ACKNOWLEDGED
Figure 1. SMBus Protocols
A
tLOW
B
C
tHIGH
D
E
F
G
H
I
J
K
L
M
SMBCLK
SMBDATA
tSU:STA tHD:STA
tSU:STO tBUF
tSU:DAT
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO 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
Figure 2. SMBus Write Timing Diagram
www.analog.com
Analog Devices │ 6
MAX6642
±1°C, SMBus-Compatible Remote/
Local Temperature Sensor with
Overtemperature Alarm
Table 1. Main Temperature Register
(High Byte) Data Format
register was previously selected by a Write Byte instruction. Use caution when using the shorter protocols in
multimaster systems, as a second master could overwrite
the command byte without informing the first master.
TEMP (°C)
DIGITAL OUTPUT
130.00
1 000 0010
127.00
0 111 1111
126.00
0 111 1110
25
0 001 1001
0.00
0 000 0000
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