MAX6695AUB ,Dual Remote/Local Temperature Sensors with SMBus Serial InterfaceMAX6695/MAX669619-3183; Rev 1; 5/04Dual Remote/Local Temperature Sensors withSMBus Serial Interface
MAX6695AUB+ ,Dual Remote/Local Temperature Sensors with SMBus Serial InterfaceFeaturesThe MAX6695/MAX6696 are precise, dual-remote, and ♦ Measure One Local and Two Remotelocal d ..
MAX6695AUB+T ,Dual Remote/Local Temperature Sensors with SMBus Serial InterfaceFeaturesThe MAX6695/MAX6696 are precise, dual-remote, and ♦ Measure One Local and Two Remotelocal d ..
MAX6695AUB-T ,Dual Remote/Local Temperature Sensors with SMBus Serial InterfaceApplicationsALERT INTERRUPT MAX6695TO μPNotebook ComputersTO CLOCKOT1DXNTHROTTLINGDesktop Computers ..
MAX6695YAUB+ ,Dual Remote/Local Temperature Sensors with SMBus Serial InterfaceApplicationsALERT INTERRUPT MAX6695TO μPNotebook ComputersTO CLOCKOT1DXNTHROTTLINGDesktop Computers ..
MAX6696AEE ,Dual Remote/Local Temperature Sensors with SMBus Serial InterfaceApplications DXNTHROTTLINGTO SYSTEMOT2Notebook ComputersSHUTDOWNDesktop ComputersServers DXP2GNDWor ..
MB3771PF-G-BND-JNE1 , ASSP For power supply applications BIPOLAR Power Supply Monitor
MB3771PS ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
MB3771PS ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
MB3773 ,Power Supply Monitor with Watch-Dog TimerFUJITSU SEMICONDUCTORDS04-27401-4EDATA SHEETASSPPower Supply Monitor with Watch-Dog TimerMB3773n DE ..
MB3775 ,SWITCHING REGULATOR CONTROLLERFUJITSU SEMICONDUCTORDS04-27204-3EDATA SHEETASSPSWITCHING REGULATOR CONTROLLERMB3775LOW VOLTAGE DUA ..
MB3775PF , SWITCHING REGULATOR CONTROLLER
MAX6695AUB-MAX6696AEE
Dual Remote/Local Temperature Sensors with SMBus Serial Interface
General DescriptionThe MAX6695/MAX6696 are precise, dual-remote, and
local digital temperature sensors. They accurately mea-
sure the temperature of their own die and two remote
diode-connected transistors, and report the tempera-
ture 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 func-
tion autonomously with a programmable conversion
rate, which allows control of supply current and temper-
ature update rate to match system needs. For conver-
sion 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 be-
tween +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 ALERTout-
put, the MAX6695/MAX6696 feature two overtempera-
ture limit indicators (OT1and OT2), which are active
only while the temperature is above the corresponding
programmable temperature limits. The OT1and OT2
outputs are typically used for fan control, clock throt-
tling, 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.
ApplicationsNotebook Computers
Desktop Computers
Servers
Workstations
Test and Measurement Equipment
FeaturesMeasure One Local and Two Remote
Temperatures11-Bit, 0.125°C Resolution High Accuracy ±1.5°C (max) from +60°C to +100°C
(Remote)ACPI CompliantProgrammable Under/Overtemperature AlarmsProgrammable Conversion Rate Three Alarm Outputs: ALERT, OT1, and OT2SMBus/I2C™-Compatible Interface
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
Ordering Information
Typical Operating Circuit19-3183; Rev 1; 5/04
SMBus is a trademark of Intel Corp.
Pin Configurations appear at end of data sheet.µMAX is a registered trademark of Maxim Integrated Products, Inc.
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
ABSOLUTE MAXIMUM RATINGSStresses 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 (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 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)
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
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)
Note 1:Based on diode ideality factor of 1.008.
Note 2:Specifications are guaranteed by design, not production tested.
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
Typical Operating Characteristics(VCC= 3.3V, TA= +25°C, unless otherwise noted.)
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
MAX6695/MAX6696
Detailed DescriptionThe MAX6695/MAX6696 are temperature sensors
designed to work in conjunction with a microprocessor
or other intelligence in temperature monitoring, protec-
tion, or control applications. Communication with the
MAX6695/MAX6696 occurs through the SMBus serial
interface and dedicated alert pins. The overtempera-
ture alarms OT1and OT2are asserted if the software-
programmed temperature thresholds are exceeded.
OT1and OT2can be connected to a fan, system shut-
down, 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 slow-
er 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 MultiplexerThe MAX6695/MAX6696 averaging ADC (Figure 1) inte-
grates over a 62.5ms or 125ms period (each channel,
typ), depending on the conversion rate (see Electrical
Characteristicstable). The use of an averaging ADC
attains excellent noise rejection.
The MAX6695/MAX6696 multiplexer (Figure 1) automat-
ically steers bias currents through the remote and local
diodes. The ADC and associated circuitry measure
each diode’s forward voltages and compute the tem-
perature 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 dif-
ferential measurement. Resistance in series with the
remote diode causes about +1/2°C error per ohm.
A/D Conversion SequenceA conversion sequence consists of a local temperature
measurement and two remote temperature measure-
ments. Each time a conversion begins, whether initiat-
ed 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 con-
version. 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 Functionssection) 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 SelectionThe 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 dis-
crete diode-connected transistor.
Effect of Ideality FactorThe accuracy of the remote temperature measurements
depends on the ideality factor (n) of the remote “diode”
(actually a transistor). The MAX6695/MAX6696 are opti-
mized 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 nNOMINALis 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
nNOMIMALfor 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 mea-
sured 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 ResistanceSeries resistance (RS) with a sensing diode contributes
additional error. For nominal diode currents of 10µA
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
and 100µA, the change in the measured voltage due to
series resistance is:
Since 1°C corresponds to 198.6µV, series resistance
contributes a temperature offset of:
Assume that the sensing diode being measured has a
series resistance of 3Ω. The series resistance con-
tributes a temperature offset of:
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 cal-
culated 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.
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial InterfaceFigure 1. MAX6695/MAX6696 Functional Diagram
MAX6695/MAX6696In this example, the effect of the series resistance and
the ideality factor partially cancel each other.
Discrete Remote DiodesWhen 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 rela-
tively 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 tempera-
ture, 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 <150, for
example) indicate that the manufacturer has good
process controls and that the devices have consistent
VBEcharacteristics.
Manufacturers of discrete transistors do not normally
specify or guarantee ideality factor. This is normally not
a problem since good-quality discrete transistors tend
to have ideality factors that fall within a relatively narrow
range. We have observed variations in remote tempera-
ture readings of less than ±2°C with a variety of dis-
crete transistors. Still, it is good design practice to
verify good consistency of temperature readings with
several discrete transistors from any manufacturer
under consideration.
Thermal Mass and Self-HeatingWhen sensing local temperature, these temperature
sensors are intended to measure the temperature of the
PC board to which they are soldered. The leads pro-
vide a good thermal path between the PC board traces
and the die. As with all IC temperature sensors, thermal
conductivity between the die and the ambient air is
poor by comparison, making air temperature measure-
ments impractical. Because the thermal mass of the PC
board is far greater than that of the MAX6695/
MAX6696, the device follows temperature changes on
the PC board with little or no perceivable delay.
When measuring the temperature of a CPU or other IC
with an on-chip sense junction, thermal mass has virtu-
ally no effect; the measured temperature of the junction
tracks the actual temperature within a conversion cycle.
When measuring temperature with discrete remote
transistors, the best thermal response times are
obtained with transistors in small packages (i.e., SOT23
or SC70). Take care to account for thermal gradients
between the heat source and the sensor, and ensure
that stray air currents across the sensor package do
not interfere with measurement accuracy.
Self-heating does not significantly affect measurement
accuracy. Remote-sensor self-heating due to the diode
current source is negligible. For local temperature mea-
surements, the worst-case error occurs when autocon-
verting at the fastest rate and simultaneously sinking
maximum current at the ALERToutput. For example,
with VCC= 3.6V, a 4Hz conversion rate and ALERT
sinking 1mA, the typical power dissipation is:
θJ-Afor the 16-pin QSOP package is about +120°C/W,
so assuming no copper PC board heat sinking, the
resulting temperature rise is:
Even under these worst-case circumstances, it is diffi-
cult to introduce significant self-heating errors.
ADC Noise FilteringThe integrating ADC has good noise rejection for low-
frequency signals such as power-supply hum. In envi-
ronments with significant high-frequency EMI, connect
an external 2200pF capacitor between DXP_ and DXN.
Larger capacitor values can be used for added filter-
ing, but do not exceed 3300pF because it can intro-
duce errors due to the rise time of the switched current
source. High-frequency noise reduction is needed for
high-accuracy remote measurements. Noise can be
reduced with careful PC board layout as discussed in
the PC Board Layoutsection.
Low-Power Standby ModeStandby mode reduces the supply current to less than
10µA by disabling the ADC. Enter hardware standby
(MAX6696 only) by forcing STBYlow, or enter software
standby by setting the RUN/STOP bit to 1 in the config-
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
uration byte register. Hardware and software standbys
are very similar; all data is retained in memory, and the
SMBus interface is alive and listening for SMBus com-
mands but the SMBus timeout is disabled. The only dif-
ference is that in software standby mode, the one-shot
command initiates a conversion. With hardware stand-
by, the one-shot command is ignored. Activity on the
SMBus causes the device to draw extra supply current.
Driving STBYlow overrides any software conversion
command. If a hardware or software standby command
is received while a conversion is in progress, the con-
version cycle is interrupted, and the temperature regis-
ters are not updated. The previous data is not changed
and remains available.
SMBus Digital InterfaceFrom a software perspective, the MAX6695/MAX6696
appear as a series of 8-bit registers that contain tem-
perature 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 same SMBus slave
address provides access to all functions.
The MAX6695/MAX6696 employ four standard SMBus
protocols: Write Byte, Read Byte, Send Byte, and
Receive Byte (Figure 2). The shorter Receive Byte proto-
col allows quicker transfers, provided that the correct
data register was previously selected by a Read Byte
instruction. Use caution with the shorter protocols in mul-
timaster systems, since a second master could overwrite
the command byte without informing the first master.
When the conversion rate control register is set ≥06h,
temperature data can be read from the read internal
temperature (00h) and read external temperature (01h)
registers. The temperature data format in these regis-
ters is 7 bits + sign in two’s-complement form for each
channel, with the LSB representing 1°C (Table 2). The
MSB is transmitted first. Use bit 3 of the configuration
register to select the registers corresponding to remote
1 or remote 2.
When the conversion rate control register is set ≤05h,
temperature data can be read from the read internal
temperature (00h) and read external temperature (01h)
registers, the same as for faster conversion rates. An
additional 3 bits can be read from the read external
extended temperature register (10h) and read internal
MAX6695/MAX6696
Dual Remote/Local Temperature Sensors with
SMBus Serial InterfaceFigure 2. SMBus Protocols
MAX6695/MAX6696extended temperature register (11h) (Table 3), which
extends the temperature data to 10 bits + sign and the
resolution to +0.125°C per LSB (Table 4).
When a conversion is complete, the main register and
the extended register are updated almost simultane-
ously. Ensure that no conversions are completed
between reading the main and extended registers so
that when data that is read, both registers contain the
result of the same conversion.
To ensure valid extended data, read extended resolu-
tion temperature data using one of the following
approaches:Put the MAX6695/MAX6696 into standby mode by
setting bit 6 of the configuration register to 1. Read
the contents of the data registers. Return to run
mode by setting bit 6 to zero.Put the MAX6695/MAX6696 into standby mode by
setting bit 6 of the configuration register to 1. Initiate
a one-shot conversion using Send Byte command
0Fh. When this conversion is complete, read the
contents of the temperature data registers.
Diode Fault AlarmThere is a continuity fault detector at DXP_ that detects
an open circuit between DXP_ and DXN, or a DXP_
short to VCC, GND, or DXN. If an open or short circuit
exists, the external temperature register (01h) is loaded
with 1000 0000. Bit 2 (diode fault) of the status registers
is correspondingly set to 1. The ALERToutput asserts
for open diode faults but not for shorted diode faults.
Immediately after power-on reset (POR), the status reg-
ister indicates that no fault is present until the end of
the first conversion. After the conversion is complete,
any diode fault is indicated in the appropriate status
register. Reading the status register clears the diode
fault bit in that register, and clears the ALERToutput if
set. If the diode fault is present after the next conver-
sion, the status bit will again be set and the ALERTout-
put will assert if the fault is an open diode fault.
Alarm Threshold RegistersSix registers, WLHO, WLLM, WRHA (1 and 2), and
WRLN (1 and 2), store ALERTthreshold values. WLHO
and WLLM, are for
internalALERThigh-temperature
and low-temperature limits, respectively. Likewise,
WRHA and WRLN are for externalchannel 1 and chan-
nel 2 high-temperature and low-temperature limits,
respectively (Table 5). If either measured temperature
equals or exceeds the corresponding ALERTthreshold
value, the ALERToutput is asserted.The POR state of
both internal and external ALERThigh-temperature limit
registers is 0100 0110 or +70°C.
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
