ESD Protection (all pins, Human Body Model) ................±2000V
Junction Temperature ......................................................+150°C
Operating Temperature Range .........................-55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Soldering Temperature (reflow) .......................................+260°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
= -55°C to +125°C, unless otherwise specified. Typical values are at V
CC
= 3.3V and T
A
= +100°C.) (Note 1)
PARAMETER
Supply Voltage
Temperature Resolution
V
CC
= 3.3V, T
A
= +100°C,
T
RJ
= +60°C to +145°C
Remote Temperature Error
V
CC
= 3.3V, T
A
= +60°C to +100°C,
T
RJ
= +25°C to +145°C
V
CC
= 3.3V, T
A
= +0°C to +100°C,
T
RJ
= +0°C to +145°C
Local Temperature Error
Supply Sensitivity of
Temperature Error
Undervoltage Lockout (UVLO)
Threshold
UVLO Hysteresis
Power-On-Reset (POR) Threshold
POR Threshold Hysteresis
Standby Supply Current
Operating Current
Average Operating Current
Conversion Time
Conversion Time Error
DXP and DXN Leakage Current
Remote-Diode Source Current
I
RJ
Standby mode
High level
Low level
80
8
100
10
t
CONV
SMBus static
During conversion
0.25 conversions per second
2 conversions per second
From stop bit to conversion completion
95
-25
40
250
125
V
CC
falling edge
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
SYMBOL
V
CC
CONDITIONS
MIN
3.0
0.125
11
-1.0
-1.6
-3.2
-2.0
-3.0
±0.2
2.7
90
2.0
90
3
12
0.08
80
400
156
+25
100
120
12
2.95
+1.0
+1.6
+3.2
+2.0
+3.0
°C
°C/V
V
mV
V
mV
μA
mA
μA
ms
%
nA
μA
°C
TYP
MAX
5.5
UNITS
V
°C
Bits
2
+145°C Precision SMBus-Compatible Remote/
Local Sensors with Overtemperature Alarms
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 3.0V to 5.5V, T
A
= -55°C to +125°C, unless otherwise specified. Typical values are at V
CC
= 3.3V and T
A
= +100°C.) (Note 1)
PARAMETER
ALERT, OVERT
Output Low Voltage
Output High Leakage Current
Logic Input Low Voltage
Logic Input High Voltage
Input Leakage Current
Output Low-Sink Current
Input Capacitance
Serial Clock Frequency
Bus Free Time Between STOP
and START Condition
Repeat START Condition Setup
Time
START Condition Hold Time
STOP Condition Setup Time
Clock Low Period
Clock High Period
Data Setup Time
Data Hold Time
Receive SCLK/SDA Rise Time
Receive SCLK/SDA Fall Time
Pulse Width of Spike
Suppressed
SMBus Timeout
V
IL
V
IH
I
LEAK
I
SINK
C
IN
f
SCLK
t
BUF
t
SU:STA
t
HD:STA
t
SU:STO
t
LOW
t
HIGH
t
SU:DAT
t
HD:DAT
t
R
t
F
t
SP
t
TIMEOUT
SDA low period for interface reset
0
25
37
(Note 4)
10% of SDA to 90% of SCLK
90% of SCLK to 90% of SDA
10% to 10%
90% to 90%
(Note 3)
4.7
4.7
4
4
4.7
4
250
250
1
300
50
55
V
CC
= 3.0V
V
CC
= 5.5V
V
IN
= V
GND
or V
CC
V
OL
= 0.6V
2.2
2.6
-1
6
5
100
+1
I
SINK
= 1mA
I
SINK
= 4mA
V
OH
= 5.5V
0.4
0.6
1
0.8
V
μA
V
V
μA
mA
pF
kHz
μs
μs
μs
μs
μs
μs
ns
ns
μs
ns
ns
ms
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX6646/MAX6647/MAX6649
SMBus-COMPATIBLE INTERFACE (SCLK AND SDA)
SMBus-COMPATIBLE TIMING
(Note 2)
Note 1:
Note 2:
Note 3:
Note 4:
All parameters tested at a single temperature. 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
+145°C Precision SMBus-Compatible Remote/
Local Sensors with Overtemperature Alarms
MAX6646/MAX6647/MAX6649
Typical Operating Characteristics
(V
CC
= 3.3V, T
A
= +25°C, unless otherwise noted.)
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6649 toc01
OPERATING SUPPLY CURRENT
vs. CONVERSION RATE
MAX6649 toc02
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
1.5
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
-1.5
T
A
= +85°C
FAIRCHILD 2N3906
0
25
50
75
100
125
MAX6649 toc03
5.0
STANDBY SUPPLY CURRENT (μA)
400
OPERATING SUPPLY CURRENT (μA)
2.0
4.5
300
4.0
200
3.5
3.0
100
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
0
0.63
0.13
0.25
0.50
1.00
2.00 4.00
CONVERSION RATE (Hz)
-2.0
TEMPERATURE (°C)
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX6649 toc04
TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6649 toc05
LOCAL TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
8
TEMPERATURE ERROR (°C)
7
6
5
4
3
2
1
0
-1
-2
LOCAL ERROR
REMOTE ERROR
V
IN
= AC-COUPLED TO DXN
V
IN
= 100mV
P-P
MAX6649 toc06
1.0
0.5
TEMPERATURE ERROR (°C)
0
-0.5
-1.0
-1.5
-2.0
0
25
50
75
100
5
LOCAL ERROR
4
TEMPERATURE ERROR (°C)
3
2
1
0
-1
-2
V
CC
= SQUARE WAVE APPLIED TO
V
CC
WITH NO BYPASS CAPACITOR
REMOTE ERROR
9
125
0.1
1
10
100
1k
10k
100k
1
10
100
1k
10k
100k
TEMPERATURE (°C)
FREQUENCY (Hz)
FREQUENCY (Hz)
TEMPERATURE ERROR
vs. DIFFERENTIAL-MODE NOISE FREQUENCY
MAX6649 toc07
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
MAX6649 toc08
2.0
1.5
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
1
10
100
1k
10k
1
0
TEMPERATURE ERROR (°C)
-1
-2
-3
-4
-5
0.100
100k
1.000
10.000
100.000
FREQUENCY (Hz)
DXP-DXN CAPACITANCE (nF)
4
+145°C Precision SMBus-Compatible Remote/
Local Sensors with Overtemperature Alarms
Pin Description
PIN
1
NAME
V
CC
FUNCTION
Supply Voltage Input, 3V to 5.5V. Bypass V
CC
to GND with a 0.1μF capacitor. A 200
recommended but not required for additional noise filtering.
series resistor is
MAX6646/MAX6647/MAX6649
2
3
4
5
DXP
DXN
OVERT
GND
Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode Channel.
DO NOT
LEAVE DXP UNCONNECTED;
connect DXP to DXN if no remote diode is used. Place a 2200pF
capacitor between DXP and DXN for noise filtering.
Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally connected to ground.
Overtemperature Alert/Interrupt Output, Open Drain.
OVERT
is logic low when the temperature is above
the software-programmed threshold.
Ground
SMBus Alert (Interrupt) Output, Open Drain.
ALERT
asserts when temperature exceeds limits (high or
low temperature).
ALERT
stays asserted until acknowledged by either reading the status register or by
successfully responding to an alert response address, provided that the fault condition no longer
exists. See the
ALERT
Interrupts
section.
SMBus Serial-Data Input/Output, Open Drain
SMBus Serial-Clock Input
6
ALERT
7
8
SDA
SCLK
Detailed Description
The MAX6646/MAX6647/MAX6649 are temperature sen-
sors designed to work in conjunction with a microproces-
sor or other intelligence in thermostatic, process-control,
or monitoring applications. Communication with the
MAX6646/MAX6647/MAX6649 occurs through the
SMBus-compatible serial interface and dedicated alert
and overtemperature outputs.
ALERT
asserts if the mea-
sured local or remote temperature is greater than the
software-programmed
ALERT
high limit or less than the
ALERT
low limit in the MAX6649.
ALERT
also asserts, in
the MAX6649, if the remote-sensing diode pins are short-
ed or unconnected. The overtemperature alarm,
OVERT,
asserts if the software-programmed
OVERT
limit is
exceeded.
OVERT
can be connected to fans, a system
shutdown, a clock throttle control, or other thermal-man-
agement circuitry.
The MAX6646/MAX6647/MAX6649 convert temperatures
to digital data either at a programmed rate or in single
conversions. Temperature data is represented as 11 bits,
with the LSB equal to 0.125°C. The “main” temperature
data registers (at addresses 00h and 01h) are 8-bit regis-
ters that represent the data as 8 bits with the full-scale
reading indicating the diode fault status (Table 1). The
remaining 3 bits of temperature data are available in the
“extended” registers at addresses 11h and 10h (Table 2).
ADC and Multiplexer
The averaging ADC integrates over a 60ms period
(each channel, typically), 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 results of the unused channel can be ignored.
If the remote-diode channel is unused, connect DXP to
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