19-3183; Rev 3; 4/11
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
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 output, 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.
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
♦ Compatible with 65nm Process Technology
(Y Versions)
Ordering Information
PART
TEMP RANGE
MAX6695AUB+
-40°C to +125°C
10 μMAX
PIN-PACKAGE
MAX6695YAUB+
-40°C to +125°C
10 μMAX
MAX6696AEE+
-40°C to +125°C
16 QSOP
MAX6696YAEE+
-40°C to +125°C
16 QSOP
Devices are also available in tape-and-reel packages. Specify
tape and reel by adding “T” to the part number when ordering.
+Denotes a lead(Pb)-free/RoHS-compliant package.
Typical Operating Circuit
0.1μF
47Ω
+3.3V
10kΩ
EACH
CPU
DXP1
VCC
SMBDATA
SMBCLK
Applications
MAX6695
DXN
Servers
CLOCK
ALERT
INTERRUPT
TO μP
OT1
TO CLOCK
THROTTLING
OT2
TO SYSTEM
SHUTDOWN
Notebook Computers
Desktop Computers
DATA
Workstations
DXP2
Test and Measurement Equipment
GND
GRAPHICS
PROCESSOR
Typical Operating Circuits continued at end of data sheet.
μMAX is a registered trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
________________________________________________________________ Maxim Integrated Products
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
MAX6695/MAX6696
General Description
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
ABSOLUTE MAXIMUM RATINGS
VCC ...........................................................................-0.3V to +6V
DXP1, DXP2................................................-0.3V to (VCC + 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 (TA = +70°C)
10-Pin μMAX (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
Soldering Temperature (reflow) .......................................+260°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 +3.6V, TA = 0°C to +125°C, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25°C)
PARAMETER
Supply Voltage
SYMBOL
CONDITIONS
VCC
MIN
3.0
Standby Supply Current
SMBus static, ADC in idle state
Operating Current
Interface inactive, ADC active
0.5
Conversion rate = 0.125Hz
Average Operating Current
Remote Temperature Error
(Note 1)
mA
Conversion rate = 4Hz
500
1000
TRJ = +25°C to +100°C
(TA = +45°C to +85°C)
-1.5
+1.5
TRJ = 0°C to +125°C (TA = +25°C to +100°C)
-3.0
+3.0
TRJ = -40°C to +125°C (TA = 0°C to +125°C)
-5.0
-2.0
+2.0
-3.0
+3.0
TA = 0°C to +125°C
-4.5
+4.5
TA = -40°C to +125°C
+3.0
TA = +45°C to +85°C
-3.8
TA = +25°C to +100°C
-4.0
TA = 0°C to +125°C
-4.2
Falling edge of VCC disables ADC
°C
°C
-4.4
1.3
1.45
1.6
2.2
2.8
2.95
V
mV
Channel 1 rate 4Hz, channel 2 / local rate
2Hz (conversion rate register 05h)
112.5
Channel 1 rate 8Hz, channel 2 / local rate
4Hz (conversion rate register 06h)
56.25
62.5
68.75
High level
80
100
120
Low level
8
10
12
125
V
mV
90
IRJ
°C
+5.0
500
UVLO
μA
+3.0
TA = +25°C to +100°C
VCC, falling edge (Note 2)
Conversion Time
2
1
70
Undervoltage Lockout Hysteresis
Remote-Diode Source Current
μA
500
POR Threshold Hysteresis
Undervoltage Lockout Threshold
V
10
35
TA = -40°C to +125°C
Power-On Reset Threshold
UNITS
3.6
250
TA = +45°C to +85°C
Local Temperature Error
(MAX6695Y/MAX6696Y)
MAX
Conversion rate = 1Hz
TRJ = -40°C to +125°C (TA = -40°C)
Local Temperature Error
TYP
137.5
ms
_______________________________________________________________________________________
μA
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
(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
ALERT, OT1, OT2
Output Low Sink Current
VOL = 0.4V
6
mA
Output High Leakage Current
VOH = 3.6V
1
μA
0.3
V
INPUT PIN, ADD0, ADD1 (MAX6696)
Logic Input Low Voltage
VIL
Logic Input High Voltage
VIH
2.9
V
INPUT PIN, RESET, STBY (MAX6696)
Logic Input Low Voltage
VIL
Logic Input High Voltage
VIH
2.1
ILEAK
-1
Input Leakage Current
0.8
V
+1
μA
0.8
V
±1
μA
6
mA
V
SMBus INTERFACE (SMBCLK, SMBDATA, STBY)
Logic Input Low Voltage
Logic Input High Voltage
Input Leakage Current
VIL
VIH
ILEAK
Output Low Sink Current
IOL
Input Capacitance
CIN
2.1
V
VIN = GND or VCC
VOL = 0.6V
5
pF
SMBus-COMPATIBLE TIMING (Figures 4 and 5) (Note 2)
Serial Clock Frequency
f SCL
10
Bus Free Time Between STOP
and START Condition
tBUF
4.7
μs
Repeat START Condition Setup
Time
t SU:STA
4.7
μs
90% of SMBCLK to 90% of SMBDATA
100
kHz
START Condition Hold Time
tHD:STA
10% of SMBDATA to 90% of SMBCLK
4
μs
STOP Condition Setup Time
t SU:STO
90% of SMBCLK to 90% of SMBDATA
4
μs
μs
Clock Low Period
tLOW
10% to 10%
4
Clock High Period
tHIGH
90% to 90%
4.7
μs
ns
Data Setup Time
t SU:DAT
250
Data Hold Time
tHD:DAT
300
SMB Rise Time
tR
1
μs
SMB Fall Time
tF
300
ns
40
ms
SMBus Timeout
SMBDATA low period for interface reset
20
ns
30
Note 1: Based on diode ideality factor of 1.008.
Note 2: Specifications are guaranteed by design, not production tested.
_______________________________________________________________________________________
3
MAX6695/MAX6696
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VCC = 3.3V, TA = +25°C, unless otherwise noted.)
AVERAGE OPERATING SUPPLY CURRENT
vs. CONVERSION RATE CONTROL REGISTER VALUE
3
2
1
500
4
TEMPERATURE ERROR (°C)
4
5
MAX6695 toc02
5
600
OPERATING SUPPLY CURRENT (μA)
MAX6695 toc01
STANDBY SUPPLY CURRENT (μA)
6
TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
400
300
200
MAX6695 toc03
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
3
REMOTE CHANNEL1
2
1
0
-1
REMOTE CHANNEL2
-2
100
-3
0
-5
-4
0
3.1
3.2
3.3
3.4
3.5
1
2
3
4
5
6
7
-50
-25
0
25
50
75
100
125
CONVERSION RATE CONTROL REGISTER VALUE (hex)
REMOTE TEMPERATURE (°C)
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
TEMPERATURE ERROR
vs. DIFFERENTIAL NOISE FREQUENCY
2
TEMPERATURE ERROR (°C)
3
2
1
0
-1
-2
-3
REMOTE CHANNEL2
1
0
REMOTE CHANNEL1
-1
VIN = 10mVP-P
REMOTE CHANNEL2
2
TEMPERATURE ERROR (°C)
4
3
MAX6695 toc06
3
MAX6695 toc04
5
TEMPERATURE ERROR (°C)
0
3.6
SUPPLY VOLTAGE (V)
MAX6695 toc05
3.0
1
0
REMOTE CHANNEL1
-1
-2
-2
-4
-5
-25
0
25
50
75
100
125
1
10
0.001
100
0.01
0.1
1
10
100
DIE TEMPERATURE (°C)
DXP-DXN CAPACITANCE (nF)
FREQUENCY (MHz)
REMOTE TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
LOCAL TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
REMOTE CHANNEL2
1
0
REMOTE CHANNEL1
-1
2
1
0
-1
-2
-2
0.001
0.01
0.1
1
FREQUENCY (MHz)
10
100
10mVP-P
2
REMOTE CHANNEL2
1
0
REMOTE CHANNEL1
-1
-2
-3
-3
3
MAX6695 toc08
100mVP-P
TEMPERATURE ERROR (°C)
2
3
MAX6695 toc07b
100mVP-P
TEMPERATURE ERROR (°C)
MAX6695 toc07a
3
4
-3
-3
-50
TEMPERATURE ERROR (°C)
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
-3
0.001
0.01
0.1
1
FREQUENCY (MHz)
10
100
0.001
0.01
0.1
1
FREQUENCY (Hz)
_______________________________________________________________________________________
10
100
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
PIN
MAX6695
MAX6696
1
2
NAME
FUNCTION
VCC
Supply Voltage Input, +3V to +3.6V. Bypass to GND with a 0.1μF capacitor. A 47
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 Remote-Diode
Channel 1. DO NOT LEAVE DXP1 UNCONNECTED; connect DXP1 to DXN if no
remote diode is used. Place a 2200pF capacitor between DXP1 and DXN for noise
filtering.
3
4
DXN
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 Remote-Diode
Channel 2. DO NOT LEAVE DXP2 UNCONNECTED; connect DXP2 to DXN if no
remote diode is used. Place a 2200pF capacitor between DXP2 and DXN for noise
filtering.
5
10
OT1
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
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.
8
11
ALERT
9
12
SMBDATA
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.
—
15
STBY
Hardware Standby Input. Pull STBY low to put the device into standby mode.
All registers’ data are maintained.
SMBus Serial-Data Input/Output, Open Drain
_______________________________________________________________________________________
5
MAX6695/MAX6696
Pin Description
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
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 VBE above 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
6
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 (not the
MAX6695Y/MAX6696Y) 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 nNOMINAL is used to measure the temperature of
a diode with a different ideality factor n1. The measured
temperature TM can be corrected using:
⎛
⎞
n1
TM = T ACTUAL × ⎜
⎟
⎝ nNOMINAL ⎠
where temperature is measured in Kelvin and
nNOMIMAL 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:
⎛n
⎞
⎛ 1. 008 ⎞
= TM × (1. 00599 )
T ACTUAL = TM × ⎜ NOMINAL ⎟ = TM × ⎜
⎝ 1. 002 ⎟⎠
n1
⎝
⎠
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
_______________________________________________________________________________________
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
MAX6695/MAX6696
VCC
(RESET)
RESET/
UVLO
CIRCUITRY
3
DXP1
MUX
DXN
DXP2
REMOTE1
REMOTE2
CONTROL
LOGIC
ADC
LOCAL
DIODE FAULT
ALERT
(STBY)
SMBus
S
Q
8
READ
SMBDATA
8
WRITE
SMBCLK
R
REGISTER BANK
7
COMMAND BYTE
REMOTE TEMPERATURES
OT1
Q
S
(ADD0)
ADDRESS
DECODER
(ADD1)
LOCAL TEMPERATURES
R
ALERT THRESHOLD
ALERT RESPONSE ADDRESS
OT2
OT1 THRESHOLDS
Q
S
R
OT2 THRESHOLDS
() ARE FOR MAX6696 ONLY.
Figure 1. MAX6695/MAX6696 Functional Diagram
and 100μA, the change in the measured voltage due to
series resistance is:
ΔVM = (100μ A − 10μ A) × R S = 90μ A × R S
Since 1°C corresponds to 198.6μV, series resistance
contributes a temperature offset of:
μV
90
Ω = 0 . 453 °C
μV
Ω
198 . 6
°C
Assume that the sensing diode being measured has a
series resistance of 3Ω. The series resistance contributes a temperature offset of:
°C
3Ω × 0. 453
= + 1 . 36 °C
Ω
The effects of the ideality factor and series resistance
are additive. If the diode has an ideality factor of 1.002
and series resistance of 3Ω, the total offset can be calculated by adding error due to series resistance with
error due to ideality factor:
1.36°C - 2.13°C = -0.77°C
for a diode temperature of +85°C.
_______________________________________________________________________________________
7
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
In this example, the effect of the series resistance and
the ideality factor partially cancel each other.
Discrete Remote Diodes
When the remote-sensing diode is a discrete transistor,
its collector and base must be connected together.
Table 1 lists examples of discrete transistors that are
appropriate for use with the MAX6695/MAX6696.
The transistor must be a small-signal type with a relatively high forward voltage; otherwise, the A/D input
voltage range can be violated. The forward voltage at
the highest expected temperature must be greater than
0.25V at 10μA, and at the lowest expected temperature, the forward voltage must be less than 0.95V at
100μA. Large power transistors must not be used. Also,
ensure that the base resistance is less than 100Ω. Tight
specifications for forward current gain (50 < ß
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