General Description
The MAX6695/MAX6696 are precise, dual-remote, and
local digital temperature sensors. They accurately measure the temperature of their own die and two remote
diode-connected transistors, and report the temperature in digital form on a 2-wire serial interface. The
remote diode is typically the emitter-base junction of a
common-collector PNP on a CPU, FPGA, GPU, or ASIC.
The 2-wire serial interface accepts standard system
management bus (SMBus™) commands such as Write
Byte, Read Byte, Send Byte, and Receive Byte to read
the temperature data and program the alarm thresholds
and conversion rate. The MAX6695/MAX6696 can function autonomously with a programmable conversion
rate, which allows control of supply current and temperature update rate to match system needs. For conversion rates of 2Hz or less, the temperature is
represented as 10 bits + sign with a resolution of
+0.125°C. When the conversion rate is 4Hz, output data
is 7 bits + sign with a resolution of +1°C. The MAX6695/
MAX6696 also include an SMBus timeout feature to
enhance system reliability.
Remote temperature sensing accuracy is ±1.5°C between +60°C and +100°C with no calibration needed.
The MAX6695/MAX6696 measure temperatures from
-40°C to +125°C. In addition to the SMBus ALERT out-
put, the MAX6695/MAX6696 feature two overtemperature limit indicators (OT1 and OT2), which are active
only while the temperature is above the corresponding
programmable temperature limits. The OT1 and OT2
outputs are typically used for fan control, clock throttling, or system shutdown.
The MAX6695 has a fixed SMBus address. The
MAX6696 has nine different pin-selectable SMBus
addresses. The MAX6695 is available in a 10-pin
µMAX®and the MAX6696 is available in a 16-pin QSOP
package. Both operate throughout the -40°C to +125°C
temperature range.
Applications
Notebook Computers
Desktop Computers
Servers
Workstations
Test and Measurement Equipment
Features
♦ Measure One Local and Two Remote
Temperatures
♦ 11-Bit, 0.125°C Resolution
♦ High Accuracy ±1.5°C (max) from +60°C to +100°C
(Remote)
♦ ACPI Compliant
♦ Programmable Under/Overtemperature Alarms
♦ Programmable Conversion Rate
♦ Three Alarm Outputs: ALERT, OT1, and OT2
♦ SMBus/I2C™-Compatible Interface
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
Typical Operating Circuit
19-3183; Rev 1; 5/04
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
PART TEMP RANGE PIN-PACKAGE
MAX6695AUB
10 µMAX
MAX6696AEE
16 QSOP
SMBus is a trademark of Intel Corp.
Pin Configurations appear at end of data sheet.
CLOCK
DATA
TO SYSTEM
SHUTDOWN
GND
OT2
SMBCLK
OT1
SMBDATA
V
CC
INTERRUPT
TO µP
0.1µF
DXN
DXP1
47Ω
10kΩ
EACH
ALERT
+3.3V
MAX6695
CPU
TO CLOCK
THROTTLING
DXP2
GRAPHICS
PROCESSOR
Typical Operating Circuits continued at end of data sheet.
I2C is a trademark of Philips Corp. Purchase of I2C components
from Maxim Integrated Products, Inc., or one of its sublicensed
Associated Companies, conveys a license under the Philips
I
2
C Patent Rights to use these components in an I2C system,
provided that the system conforms to the I
2
C Standard
Specification as defined by Philips.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
-40°C to +125°C
-40°C to +125°C
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
2 _______________________________________________________________________________________
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.
VCC...........................................................................-0.3V to +6V
DXP1, DXP2................................................-0.3V to (V
CC
+ 0.3V)
DXN ......................................................................-0.3V to +0.8V
SMBCLK, SMBDATA, ALERT ...................................-0.3V to +6V
RESET, STBY, ADD0, ADD1, OT1, OT2 ...................-0.3V to +6V
SMBDATA Current .................................................1mA to 50mA
DXN Current ......................................................................±1mA
Continuous Power Dissipation (T
A
= +70°C)
10-Pin mMAX (derate 6.9mW/°C above +70°C).......555.6mW
16-Pin QSOP (derate 8.3mW/°C above +70°C) .......666.7mW
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
ELECTRICAL CHARACTERISTICS
(VCC= +3.0V to +3.6V, TA= 0°C to +125°C, unless otherwise noted. Typical values are at VCC= +3.3V and TA= +25°C)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage V
CC
3.0 3.6 V
Standby Supply Current SMBus static, ADC in idle state 10 µA
Operating Current Interface inactive, ADC active 0.5 1 mA
Conversion rate = 0.125Hz 35 70
Conversion rate = 1Hz
500Average Operating Current
Conversion rate = 4Hz
µA
TRJ = +25°C to +100°C
(T
A
= +45°C to +85°C)
Remote Temperature Error
(Note 1)
T
RJ
= -40°C to +125°C (TA = -40°C)
°C
TA = +45°C to +85°C
TA = +25°C to +100°C
TA = 0°C to +125°C
Local Temperature Error
T
A
= -40°C to +125°C
°C
Power-On Reset Threshold VCC, falling edge (Note 2) 1.3
1.6 V
POR Threshold Hysteresis
mV
Undervoltage Lockout Threshold
UVLO Falling edge of VCC disables ADC 2.2 2.8
V
Undervoltage Lockout Hysteresis
90 mV
Channel 1 rate ≤4Hz, channel 2 / local rate
≤2Hz (conversion rate register ≤05h)
Conversion Time
Channel 1 rate ≥8Hz, channel 2 / local rate
≥4Hz (conversion rate register ≥06h)
ms
High level 80
120
Remote-Diode Source Current I
RJ
Low level 8 10 12
µA
ALERT, OT1, OT2
Output Low Sink Current VOL = 0.4V 6 mA
Output High Leakage Current VOH = 3.6V 1 µA
INPUT PIN, ADD0, ADD1 (MAX6696)
Logic Input Low Voltage V
IL
0.3 V
Logic Input High Voltage V
IH
2.9 V
250
T
= 0° C to + 125° C ( TA = + 25° C to + 100° C ) -3.0 +3.0
R J
TRJ = -40°C to +125°C (TA = 0°C to +125°C) -5.0 +5.0
-1.5 +1.5
-2.0 +2.0
-3.0 +3.0
-4.5 +4.5
112.5 125 137.5
56.25 62.5 68.75
500 1000
+3.0
+3.0
1.45
500
100
2.95
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC= +3.0V to +3.6V, TA= 0°C to +125°C, unless otherwise noted. Typical values are at VCC= +3.3V and TA= +25°C)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
INPUT PIN, RESET, STBY (MAX6696)
Logic Input Low Voltage V
IL
0.8 V
Logic Input High Voltage V
IH
2.1 V
Input Leakage Current I
LEAK
-1 +1 µA
SMBus INTERFACE (SMBCLK, SMBDATA, STBY)
Logic Input Low Voltage V
IL
0.8 V
Logic Input High Voltage V
IH
2.1 V
Input Leakage Current I
LEAK
VIN = GND or V
CC
±1 µA
Output Low Sink Current I
OL
VOL = 0.6V 6 mA
Input Capacitance C
IN
5pF
SMBus-COMPATIBLE TIMING (Figures 4 and 5) (Note 2)
Serial Clock Frequency f
SCL
10 100 kHz
Bus Free Time Between STOP
and START Condition
t
BUF
4.7 µs
Repeat START Condition Setup
Time
90% of SMBCLK to 90% of SMBDATA 4.7 µs
START Condition Hold Time
10% of SMBDATA to 90% of SMBCLK 4 µs
STOP Condition Setup Time
90% of SMBCLK to 90% of SMBDATA 4 µs
Clock Low Period t
LOW
10% to 10% 4 µs
Clock High Period t
HIGH
90% to 90% 4.7 µs
Data Setup Time
µs
Data Hold Time
µs
SMB Rise Time t
R
1µs
SMB Fall Time t
F
300 ns
SMBus Timeout SMBDATA low period for interface reset 20 30 40 ms
Note 1: Based on diode ideality factor of 1.008.
Note 2: Specifications are guaranteed by design, not production tested.
t
SU:STA
t
HD:STA
t
SU:STO
t
SU:DAT
t
HD:DAT
250
300
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC= 3.3V, TA= +25°C, unless otherwise noted.)
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6695 toc01
SUPPLY VOLTAGE (V)
STANDBY SUPPLY CURRENT (µA)
3.53.43.33.23.1
1
2
3
4
5
6
0
3.0 3.6
AVERAGE OPERATING SUPPLY CURRENT
vs. CONVERSION RATE CONTROL REGISTER VALUE
MAX6695 toc02
CONVERSION RATE CONTROL REGISTER VALUE (hex)
OPERATING SUPPLY CURRENT (µA)
321
100
200
300
400
500
600
0
07654
TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
MAX6695 toc03
REMOTE TEMPERATURE (°C)
TEMPERATURE ERROR (°C)
1007525 500-25
-4
-3
-2
-1
0
1
2
3
4
5
-5
-50 125
REMOTE CHANNEL2
REMOTE CHANNEL1
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX6695 toc04
DIE TEMPERATURE (°C)
TEMPERATURE ERROR (°C)
1007525 500-25
-4
-3
-2
-1
0
1
2
3
4
5
-5
-50 125
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
MAX6695 toc05
DXP-DXN CAPACITANCE (nF)
TEMPERATURE ERROR (°C)
3
-3
-2
-1
0
1
2
1 10 100
REMOTE CHANNEL1
REMOTE CHANNEL2
3
0.001 0.01 0.1 1 10 100
2
1
0
-1
-2
-3
TEMPERATURE ERROR
vs. DIFFERENTIAL NOISE FREQUENCY
MAX6695 toc06
FREQUENCY (MHz)
TEMPERATURE ERROR (°C)
REMOTE CHANNEL1
VIN = 10mV
P-P
REMOTE CHANNEL2
3
0.001 0.01 0.1 1 10 100
2
1
0
-2
-1
-3
REMOTE TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6695 toc07a
FREQUENCY (MHz)
TEMPERATURE ERROR (°C)
100mV
P-P
REMOTE CHANNEL2
REMOTE CHANNEL1
3
0.001 0.01 0.1 1 10 100
2
1
-1
0
-2
-3
LOCAL TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6695 toc07b
FREQUENCY (MHz)
TEMPERATURE ERROR (°C)
100mV
P-P
3
0.001 0.01 0.1 1 10 100
2
1
0
-1
-2
-3
TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
MAX6695 toc08
FREQUENCY (Hz)
TEMPERATURE ERROR (°C)
REMOTE CHANNEL1
10mV
P-P
REMOTE CHANNEL2
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
_______________________________________________________________________________________ 5
Pin Description
PIN
MAX6695 MAX6696
NAME FUNCTION
12V
CC
Supply Voltage Input, +3V to +3.6V. Bypass to GND with a 0.1µF capacitor. A
47Ω series resistor is recommended but not required for additional noise
filtering. See Typical Operating Circuit.
2 3 DXP1
Combined Remote-Diode Current Source and A/D Positive Input for RemoteDiode Channel 1. DO NOT LEAVE DXP1 FLOATING; connect DXP1 to DXN if no
remote diode is used. Place a 2200pF capacitor between DXP1 and DXN for
noise filtering.
34DXN
Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally
biased to one diode drop above ground.
4 5 DXP2
Combined Remote-Diode Current Source and A/D Positive Input for RemoteDiode Channel 2. DO NOT LEAVE DXP2 FLOATING; connect DXP2 to DXN if no
remote diode is used. Place a 2200pF capacitor between DXP2 and DXN for
noise filtering.
510OT1
Overtemperature Active-Low Output, Open Drain. OT1 is asserted low only when
the temperature is above the programmed OT1 threshold.
6 8 GND Ground
7 9 SMBCLK SMBus Serial-Clock Input
811ALERT
SMBus Alert (Interrupt) Active-Low Output, Open-Drain. Asserts when
temperature exceeds user-set limits (high or low temperature) or when a remote
sensor opens. Stays asserted until acknowledged by either reading the status
register or by successfully responding to an alert response address. See the
ALERT Interrupts section.
9 12 SMBDATA SMBus Serial-Data Input/Output, Open Drain
10 13 OT2
Overtemperature Active-Low Output, Open Drain. OT2 is asserted low only when
temperature is above the programmed OT2 threshold.
— 1, 16 N.C. No Connect
— 6 ADD1
SMBus Slave Address Select Input (Table 10). ADD0 and ADD1 are sampled
upon power-up.
— 7 RESET
Reset Input. Drive RESET high to set all registers to their default values (POR
state). Pull RESET low for normal operation.
— 14 ADD0
SMBus Slave Address Select Input (Table 10). ADD0 and ADD1 are sampled
upon power-up.
—15STBY
Hardware Standby Input. Pull STBY low to put the device into standby mode.
All registers’ data are maintained.
MAX6695/MAX6696
Detailed Description
The MAX6695/MAX6696 are temperature sensors
designed to work in conjunction with a microprocessor
or other intelligence in temperature monitoring, protection, or control applications. Communication with the
MAX6695/MAX6696 occurs through the SMBus serial
interface and dedicated alert pins. The overtemperature alarms OT1 and OT2 are asserted if the softwareprogrammed temperature thresholds are exceeded.
OT1 and OT2 can be connected to a fan, system shutdown, or other thermal-management circuitry.
The MAX6695/MAX6696 convert temperatures to digital
data continuously at a programmed rate or by selecting
a single conversion. At the highest conversion rate,
temperature conversion results are stored in the “main”
temperature data registers (at addresses 00h and 01h)
as 7-bit + sign data with the LSB equal to 1°C. At slower conversion rates, 3 additional bits are available at
addresses 11h and 10h, providing 0.125°C resolution.
See Tables 2, 3, and 4 for data formats.
ADC and Multiplexer
The MAX6695/MAX6696 averaging ADC (Figure 1) integrates over a 62.5ms or 125ms period (each channel,
typ), depending on the conversion rate (see Electrical
Characteristics table). The use of an averaging ADC
attains excellent noise rejection.
The MAX6695/MAX6696 multiplexer (Figure 1) automatically steers bias currents through the remote and local
diodes. The ADC and associated circuitry measure
each diode’s forward voltages and compute the temperature based on these voltages. If a remote channel
is not used, connect DXP_ to DXN. Do not leave DXP_
and DXN unconnected. When a conversion is initiated,
all channels are converted whether they are used or
not. The DXN input is biased at one VBEabove ground
by an internal diode to set up the ADC inputs for a differential measurement. Resistance in series with the
remote diode causes about +1/2°C error per ohm.
A/D Conversion Sequence
A conversion sequence consists of a local temperature
measurement and two remote temperature measurements. Each time a conversion begins, whether initiated automatically in the free-running autoconvert mode
(RUN/STOP = 0) or by writing a one-shot command, all
three channels are converted, and the results of the
three measurements are available after the end of conversion. Because it is common to require temperature
measurements to be made at a faster rate on one of the
remote channels than on the other two channels, the
conversion sequence is Remote 1, Local, Remote 1,
Remote 2. Therefore, the Remote 1 conversion rate is
double that of the conversion rate for either of the other
two channels.
A BUSY status bit in status register 1 (see Table 7 and
the Status Byte Functions section) shows that the
device is actually performing a new conversion. The
results of the previous conversion sequence are always
available when the ADC is busy.
Remote-Diode Selection
The MAX6695/MAX6696 can directly measure the die
temperature of CPUs and other ICs that have on-board
temperature-sensing diodes (see the Typical Operating
Circuit) or they can measure the temperature of a discrete diode-connected transistor.
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 MAX6695/MAX6696 are optimized for n = 1.008. A thermal diode on the substrate of
an IC is normally a PNP with its collector grounded. DXP_
must be connected to the anode (emitter) 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 will be different from the
data obtained with the optimum ideality factor.
Fortunately, the difference is predictable. Assume a
remote-diode sensor designed for a nominal ideality
factor n
NOMINAL
is used to measure the temperature of
a diode with a different ideality factor n1. The measured
temperature TMcan be corrected using:
where temperature is measured in Kelvin and
n
NOMIMAL
for the MAX6695/MAX6696 is 1.008.
As an example, assume you want to use the MAX6695
or MAX6696 with a CPU that has an ideality factor of
1.002. If the diode has no series resistance, the measured data is related to the real temperature as follows:
For a real temperature of +85°C (358.15K), the measured
temperature is +82.87°C (356.02K), an error of -2.13°C.
Effect of Series Resistance
Series resistance (RS) with a sensing diode contributes
additional error. For nominal diode currents of 10µA
TT
n
n
TT
ACTUAL M
NOMINAL
MM
=×
⎛
⎝
⎜
⎞
⎠
⎟
=×
⎛
⎝
⎜
⎞
⎠
⎟
=×
()
1
1 008
1 002
1 00599
.
.
.
TT
n
n
M ACTUAL
NOMINAL
=×
⎛
⎝
⎜
⎞
⎠
⎟
1
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
6 _______________________________________________________________________________________