19-2920; Rev 2; 7/09
KIT
ATION
EVALU
E
BL
AVAILA
±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 tempera-
ture 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.
Measurements can be done autonomously or in a sin-
gle-shot mode.
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.
Features
o
Dual Channel: Measures Remote and Local
Temperature
o
+0.25°C Resolution
o
High Accuracy ±1°C (max) (Remote) and
±2°C (Local) from +60°C to +100°C
o
Measures Remote Temperature Up to +150°C
o
Programmable Overtemperature Alarm
Temperature Thresholds
o
SMBus/I
2
C-Compatible Interface
o
Tiny TDFN Package with Exposed Pad
MAX6642
Ordering Information
PART
MAX6642ATT90-T
MAX6642ATT92-T
MAX6642ATT94-T
MAX6642ATT96-T
MAX6642ATT98-T
MAX6642ATT9A-T
MAX6642ATT9C-T
MAX6642ATT9E-T
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
6 TDFN-EP*
6 TDFN-EP*
6 TDFN-EP*
6 TDFN-EP*
6 TDFN-EP*
6 TDFN-EP*
6 TDFN-EP*
6 TDFN-EP*
Applications
Desktop Computers
Notebook Computers
Servers
Thin Clients
Test and Measurement
Workstations
Graphic Cards
T = Tape and reel.
*EP
= Exposed pad.
Pin Configuration and Functional Diagram appear at end of
data sheet.
Typical Operating Circuit
3.3V
0.1μF
47Ω
Selector Guide
PART
MAX6642ATT90-T
MAX6642ATT92-T
MAX6642ATT94-T
MAX6642ATT96-T
MAX6642ATT98-T
MAX6642ATT9A-T
MAX6642ATT9C-T
MEASURED TEMP RANGE
0°C to +150°C
0°C to +150°C
0°C to +150°C
0°C to +150°C
0°C to +150°C
0°C to +150°C
0°C to +150°C
TOP
MARK
AFC
AFD
AFE
AFF
AEW
AFG
AFH
AFI
μP
2200pF
V
CC
10kΩ EACH
DXP
MAX6642
SDA
DATA
CLOCK
INTERRUPT TO
μP
SCLK
ALERT
GND
MAX6642ATT9E-T
0°C to +150°C
SMBus is a trademark of Intel Corp.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
±1°C, SMBus-Compatible Remote/Local
Temperature Sensor with Overtemperature Alarm
MAX6642
ABSOLUTE MAXIMUM RATINGS
All Voltages Referenced to GND
V
CC
...........................................................................-0.3V to +6V
DXP.............................................................-0.3V to (V
CC
+ 0.3V)
SCLK, SDA,
ALERT
..................................................-0.3V to +6V
SDA,
ALERT
Current ...........................................-1mA to +50mA
Continuous Power Dissipation (T
A
= +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
(V
CC
= +3.0V to +5.5V, T
A
= -40°C to +125°C, unless otherwise specified. Typical values are at V
CC
= +3.3V and T
A
= +25°C.) (Note 1)
PARAMETER
Supply Voltage
Temperature Resolution
T
RJ
= +60°C to +100°C,
T
A
= +25°C to +85°C
T
RJ
= 0°C to +125°C
T
RJ
= +125°C to +150°C
Local Temperature Error
Supply Sensitivity of Temperature
Error
Undervoltage Lockout Threshold
Undervoltage Lockout Hysteresis
Power-On-Reset (POR) Threshold
POR Threshold Hysteresis
Standby Supply Current
Operating Current
Average Operating Current
Conversion Time
Conversion Rate
Remote-Diode Source Current
ALERT
Output-Low Sink Current
Output-High Leakage Current
V
OL
= 0.4V
V
OL
= 0.6V
V
OH
= V
CC
1
4
1
mA
µA
t
CONV
f
CONV
I
RJ
High level
Low level
80
8
From stop bit to conversion completion
106
SMBus static
During conversion
V
CC
falling edge
1.5
UVLO
Falling edge of V
CC
disables ADC
2.4
V
CC
= 3.3V
T
A
= +60°C to +100°C
T
A
= 0°C to +125°C
-1.0
-3.0
-3.5
-2.0
-3.0
±0.2
2.7
90
2.0
90
3
0.5
260
125
8
100
10
120
12
143
10
1.0
2.4
2.95
SYMBOL
V
CC
CONDITIONS
MIN
3.0
0.25
10
+1.0
+3.0
+3.5
+2.0
+3.0
°C
°C/V
V
mV
V
mV
µA
mA
µA
ms
Hz
µA
°C
TYP
MAX
5.5
UNITS
V
°C
Bits
Remote Temperature Error
V
CC
= 3.3V
2
_______________________________________________________________________________________
±1°C, SMBus-Compatible Remote/Local
Temperature Sensor with Overtemperature Alarm
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.0V to +5.5V, T
A
= -40°C to +125°C, unless otherwise specified. Typical values are at V
CC
= +3.3V and T
A
= +25°C.) (Note 1)
PARAMETER
Logic Input Low Voltage
Logic Input High Voltage
Input Leakage Current
Output Low Sink Current
Input Capacitance
SMBus TIMING
(Note 2)
Serial Clock Frequency
Bus Free Time Between STOP
and START Condition
START Condition Setup Time
Repeat START Condition Setup
Time
START Condition Hold Time
STOP Condition Setup Time
Clock Low Period
Clock High Period
Data Setup Time
Receive SCLK/SDA Rise Time
Receive SCLK/SDA Fall Time
Pulse Width of Spike Suppressed
SMBus Timeout
t
SU:STA
t
HD:STA
t
SU:STO
t
LOW
t
HIGH
t
HD:DAT
t
R
t
F
t
SP
t
TIMEOUT
SDA low period for interface reset
0
20
28
90% to 90%
10% of SDA to 90% of SCLK
90% of SCLK to 90% of SDA
10% to 10%
90% to 90%
(Note 4)
f
SCLK
t
BUF
(Note 3)
4.7
4.7
50
4
4
4.7
4
250
1
300
50
40
100
kHz
µs
µs
ns
µs
µs
µs
µs
µs
µs
ns
ns
ms
SYMBOL
V
IL
V
IH
I
LEAK
I
OL
C
IN
V
CC
= 3.0V
V
IN
= GND or 5.5V
V
OL
= 0.6V
2.2
-1
6
5
+1
CONDITIONS
MIN
TYP
MAX
0.8
UNITS
V
V
µA
mA
pF
MAX6642
SMBus-COMPATIBLE INTERFACE (SCLK and SDA)
Note 1:
Note 2:
Note 3:
Note 4:
All parameters tested at T
A
= +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 t
TIMEOUT
.
A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SCLK’s falling edge.
_______________________________________________________________________________________
3
±1°C, SMBus-Compatible Remote/Local
Temperature Sensor with Overtemperature Alarm
MAX6642
Typical Operating Characteristics
(V
CC
= 3.3V, T
A
= +25°C, unless otherwise noted.)
STANDBY SUPPLY CURRENT
vs. CLOCK FREQUENCY
4.5
SUPPLY CURRENT (μA)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.01
0.1
1
10
100
CLOCK FREQUENCY (kHz)
MAX6642 toc01
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
MAX6642 toc02
5.0
2
1
TEMPERATURE ERROR (°C)
0
-1
-2
-3
2N3906
-4
0
25
50
75
100
125
TEMPERATURE (°C)
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX 6642 toc03
TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6642 toc04
3
2
TEMPERATURE ERROR (°C)
1
0
-1
-2
-3
0
25
50
75
100
2.0
1.5
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
V
IN
= 100mV
P-P
SQUARE WAVE
APPLIED TO V
CC
WITH NO BYPASS CAPACITOR
0.01
0.1
1
10
LOCAL ERROR
REMOTE ERROR
125
-1.5
0.0001 0.001
100
TEMPERATURE (°C)
FREQUENCY (kHz)
TEMPERATURE ERROR
vs. DXP NOISE FREQUENCY
MAX6642 toc05
TEMPERATURE ERROR
vs. DXP-GND CAPACITANCE
1.0
TEMPERATURE ERROR (°C)
0
-1.0
-2.0
-3.0
-4.0
-5.0
-6.0
MAX6642 toc06
100
90
TEMPERATURE ERROR (°C)
80
70
60
50
40
30
20
10
0
0.001
0.01
0.1
1
10
LOCAL ERROR
REMOTE ERROR
V
IN
= AC-COUPLED TO DXP
V
IN
= 100mV
P-P
SQUARE WAVE
2.0
100
0.1
1
10
100
FREQUENCY (kHz)
DXP-GND CAPACITANCE (nF)
4
_______________________________________________________________________________________
±1°C, SMBus-Compatible Remote/Local
Temperature Sensor with Overtemperature Alarm
Pin Description
PIN
1
2
3
4
5
6
—
NAME
V
CC
GND
DXP
SCLK
SDA
ALERT
EP
FUNCTION
Supply Voltage Input, +3V to +5.5V. Bypass V
CC
to GND with a 0.1µF capacitor. A 47Ω series resistor is
recommended but not required for additional noise filtering.
Ground
Combined Remote-Diode Current Source and ADC Input for Remote-Diode Channel. Place a 2200pF
capacitor between DXP and GND for noise filtering.
SMBus Serial-Clock Input. May be pulled up to +5.5V regardless of V
CC
.
SMBus Serial-Data Input/Output, Open Drain. May be pulled up to +5.5V regardless of V
CC
.
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.
MAX6642
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.
remote temperature is measured eight times per sec-
ond. 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 config-
uration byte register (Table 4). All data is retained in
memory, and the SMBus interface is active and listen-
ing for SMBus commands. Standby mode is not a shut-
down 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 tempera-
ture register. The previous data is not changed and
remains available.
Supply-current drain during the 125ms conversion peri-
od is 500µA (typ). In standby mode, supply current
drops to 3µA (typ).
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 volt-
age and compute the temperature based on this volt-
age. Both channels are automatically converted once
the conversion process has started, either in free-run-
ning 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 chan-
nel. 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
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 stan-
dard 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
5
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