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MAX1617MEEMAXIM ?N/a50avaiRemote/Local Temperature Sensor with SMBus Serial Interface


MAX1617MEE ,Remote/Local Temperature Sensor with SMBus Serial InterfaceFeaturesThe MAX1617 (patents pending) is a precise digital' Two Channels: Measures Both Remote and ..
MAX1617MEE+ ,Remote/Local Temperature Sensor with SMBus Serial InterfaceMAX1617Remote/Local Temperature Sensor with SMBus Serial Interface________________
MAX1617MEE+T ,Remote/Local Temperature Sensor with SMBus Serial InterfaceFeaturesThe MAX1617 is a precise digital thermometer that♦ Two Channels: Measures Both Remote and L ..
MAX1617MEE-T ,Remote/Local Temperature Sensor with SMBus Serial InterfaceELECTRICAL CHARACTERISTICS(V = +3.3V, T = 0°C to +85°C, unless otherwise noted.) (Note 1)CC APARAME ..
MAX1617MEE-T ,Remote/Local Temperature Sensor with SMBus Serial InterfaceApplicationsPART TEMP. RANGE PIN-PACKAGEDesktop and Notebook Central Office MAX1617MEE+ -55°C to +1 ..
MAX1618MUB ,Remote Temperature Sensor with SMBus Serial InterfaceFeaturesThe MAX1618 precise digital thermometer reports the Single Channel: Measures Remote CPUtem ..
MAX4332ESA ,Single/Dual/Quad / Low-Power / Single-Supply / Rail-to-Rail I/O Op Amps with ShutdownELECTRICAL CHARACTERISTICS(V = +2.3V to +6.5V, V = 0V, V = 0V, V = (V / 2), R tied to (V / 2), V ‡ ..
MAX4332ESA ,Single/Dual/Quad / Low-Power / Single-Supply / Rail-to-Rail I/O Op Amps with ShutdownELECTRICAL CHARACTERISTICS (continued)(V = +2.3V to +6.5V, V = 0V, V = 0V, V = (V / 2), R tied to ( ..
MAX4332ESA ,Single/Dual/Quad / Low-Power / Single-Supply / Rail-to-Rail I/O Op Amps with ShutdownApplicationsMAX4331ESA -40°C to +85°C 8 SO —Portable/Battery-Powered EquipmentMAX4331EUA -40°C to + ..
MAX4332ESA+ ,Single/Dual/Quad, Low-Power, Single-Supply, Rail-to-Rail I/O Op Amps with ShutdownGeneral Description ________
MAX4333EUB ,Single/Dual/Quad / Low-Power / Single-Supply / Rail-to-Rail I/O Op Amps with ShutdownApplications MAX4334ESD -40°C to +85°C 14 SO —Selector GuidePin ConfigurationsNO. OF AMPS SHUTDOWNP ..
MAX4333EUB ,Single/Dual/Quad / Low-Power / Single-Supply / Rail-to-Rail I/O Op Amps with ShutdownELECTRICAL CHARACTERISTICS (continued)(V = +2.3V to +6.5V, V = 0V, V = 0V, V = (V / 2), R tied to ( ..


MAX1617MEE
Remote/Local Temperature Sensor with SMBus Serial Interface
________________General Description
The MAX1617 (patents pending) is a precise digital
thermometer that reports the temperature of both a
remote sensor and its own package. The remote sensor
is a diode-connected transistor—typically a low-cost,
easily mounted 2N3904 NPN type—that replaces con-
ventional thermistors or thermocouples. Remote accu-
racy is ±3°C for multiple transistor manufacturers, with
no calibration needed. The remote channel can also
measure the die temperature of other ICs, such as
microprocessors, that contain an on-chip, diode-con-
nected transistor.
The 2-wire serial interface accepts standard System
Management Bus (SMBus™) Write Byte, Read Byte,
Send Byte, and Receive Byte commands to program the
alarm thresholds and to read temperature data. The data
format is 7 bits plus sign, with each bit corresponding to
1°C, in twos-complement format. Measurements can be
done automatically and autonomously, with the conver-
sion rate programmed by the user or programmed to
operate in a single-shot mode. The adjustable rate allows
the user to control the supply-current drain.
The MAX1617 is available in a small, 16-pin QSOP sur-
face-mount package.
________________________Applications

Desktop and NotebookCentral Office
ComputersTelecom Equipment
Smart Battery PacksTest and Measurement
LAN ServersMulti-Chip Modules
Industrial Controls
____________________________Features
Two Channels: Measures Both Remote and Local
Temperatures
No Calibration RequiredSMBus 2-Wire Serial InterfaceProgrammable Under/Overtemperature AlarmsSupports SMBus Alert ResponseAccuracy:
±2°C (+60°C to +100°C, local)
±3°C (-40°C to +125°C, local)
±3°C (+60°C to +100°C, remote)
3µA (typ) Standby Supply Current70µA (max) Supply Current in Auto-Convert Mode+3V to +5.5V Supply RangeSmall, 16-Pin QSOP Package
MAX1617
Remote/Local Temperature Sensor
with SMBus Serial Interface
___________________Pin Configuration
__________Typical Operating Circuit

SMBus is a trademark of Intel Corp.
*U.S. and foreign patents pending.

†Patents Pending
MAX161
Remote/Local Temperature Sensor
with SMBus Serial Interface
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS

(VCC= +3.3V, TA= 0°C to +85°C, unless otherwise noted.)
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.
VCCto GND..............................................................-0.3V to +6V
DXP, ADD_ to GND....................................-0.3V to (VCC+ 0.3V)
DXN to GND..........................................................-0.3V to +0.8V
SMBCLK, SMBDATA, ALERT, STBYto GND...........-0.3V to +6V
SMBDATA, ALERTCurrent.................................-1mA to +50mA
DXN Current.......................................................................±1mA
ESD Protection (SMBCLK, SMBDATA, ALERT, human body model)..........................................4000V
ESD Protection (other pins, human body model)...............2000V
Continuous Power Dissipation (TA= +70°C)
QSOP (derate 8.30mW/°C above +70°C).....................667mW
Operating Temperature Range.........................-55°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +165°C
Lead Temperature (soldering, 10sec).............................+300°C
MAX161
Remote/Local Temperature Sensor
with SMBus Serial Interface
ELECTRICAL CHARACTERISTICS (continued)

(VCC= +3.3V, TA= 0°C to +85°C, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS

(VCC= +3.3V, TA= -55°C to +125°C, unless otherwise noted.) (Note 6)
__________________________________________Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
MAX161
Remote/Local Temperature Sensor
with SMBus Serial Interface
ELECTRICAL CHARACTERISTICS (continued)

(VCC= +3.3V, TA= -55°C to +125°C, unless otherwise noted.) (Note 6)
Note 1:
Guaranteed but not 100% tested.
Note 2:
Quantization error is not included in specifications for temperature accuracy. For example, if the MAX1617 device tempera-
ture is exactly +66.7°C, the ADC may report +66°C, +67°C, or +68°C (due to the quantization error plus the +1/2°C offset
used for rounding up) and still be within the guaranteed ±1°C error limits for the +60°C to +100°C temperature range. See
Table 2.
Note 3:
A remote diode is any diode-connected transistor from Table 1. TRis the junction temperature of the remote diode. See
Remote Diode Selectionfor remote diode forward voltage requirements.
Note 4:
The SMBus logic block is a static design that works with clock frequencies down to DC. While slow operation is possible, it
violates the 10kHz minimum clock frequency and SMBus specifications, and may monopolize the bus.
Note 5:
Note that a transition must internally provide at least a hold time in order to bridge the undefined region (300ns max) of
SMBCLK’s falling edge.
Note 6:
Specifications from -55°C to +125°C are guaranteed by design, not production tested.
MAX161
Remote/Local Temperature Sensor
with SMBus Serial Interface
____________________________Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)
MAX161
Remote/Local Temperature Sensor
with SMBus Serial Interface
______________________________________________________________Pin Description
_______________Detailed Description

The MAX1617 (patents pending) is a temperature sen-
sor designed to work in conjunction with an external
microcontroller (µC) or other intelligence in thermostat-
ic, process-control, or monitoring applications. The µC
is typically a power-management or keyboard con-
troller, generating SMBus serial commands by “bit-
banging” general-purpose input-output (GPIO) pins or
via a dedicated SMBus interface block.
Essentially an 8-bit serial analog-to-digital converter
(ADC) with a sophisticated front end, the MAX1617
contains a switched current source, a multiplexer, an
ADC, an SMBus interface, and associated control logic
(Figure 1). Temperature data from the ADC is loaded
into two data registers, where it is automatically com-
pared with data previously stored in four over/under-
temperature alarm registers.
ADC and Multiplexer

The ADC is an averaging type that integrates over a
60ms period (each channel, typical), with excellent
noise rejection.
The multiplexer automatically steers bias currents
through the remote and local diodes, measures their
forward voltages, and computes their temperatures.
Both channels are automatically converted once the
conversion process has started, either in free-running
or single-shot mode. If one of the two channels is not
used, the device still performs both measurements, and
the user can simply ignore the results of the unused
channel. If the remote diode channel is unused, tie DXP
to DXN rather than leaving the pins open.
The DXN input is biased at 0.65V above ground by an
internal diode to set up the analog-to-digital (A/D)
inputs for a differential measurement. The worst-case
DXP–DXN differential input voltage range is 0.25V to
0.95V.
Excess resistance in series with the remote diode caus-
es about +1/2°C error per ohm. Likewise, 200µV of off-
set voltage forced on DXP–DXN causes about 1°C error.
MAX161
Remote/Local Temperature Sensor
with SMBus Serial Interface

Figure 1. Functional Diagram
A/D Conversion Sequence
If a Start command is written (or generated automatical-
ly in the free-running auto-convert mode), both chan-
nels are converted, and the results of both
measurements are available after the end of conver-
sion. A BUSY status bit in the status byte shows that the
device is actually performing a new conversion; howev-
er, even if the ADC is busy, the results of the previous
conversion are always available.
Remote-Diode Selection

Temperature accuracy depends on having a good-qual-
ity, diode-connected small-signal transistor. Accuracy
has been experimentally verified for all of the devices
listed in Table 1. The MAX1617 can also directly mea-
sure the die temperature of CPUs and other integrated
circuits having on-board temperature-sensing diodes.
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
must be greater than 0.25V at 10µA; check to ensure
this is true at the highest expected temperature. The
forward voltage must be less than 0.95V at 100µA;
check to ensure this is true at the lowest expected tem-
perature. Large power transistors don’t work at all.
Also, ensure that the base resistance is less than 100Ω.
Tight specifications for forward-current gain (+50 to
+150, for example) indicate that the manufacturer has
good process controls and that the devices have con-
sistent VBE characteristics.
For heat-sink mounting, the 500-32BT02-000 thermal
sensor from Fenwal Electronics is a good choice. This
device consists of a diode-connected transistor, an
aluminum plate with screw hole, and twisted-pair cable
(Fenwal Inc., Milford, MA, 508-478-6000).
Thermal Mass and Self-Heating

Thermal mass can seriously degrade the MAX1617’s
effective accuracy. The thermal time constant of the
QSOP-16 package is about 140sec in still air. For the
MAX1617 junction temperature to settle to within +1°C
after a sudden +100°C change requires about five time
constants or 12 minutes. The use of smaller packages
for remote sensors, such as SOT23s, improves the situ-
ation. 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 the local diode, the
worst-case error occurs when auto-converting at the
fastest rate and simultaneously sinking maximum cur-
rent at the ALERToutput. For example, at an 8Hz rate
and with ALERTsinking 1mA, the typical power dissi-
pation is VCCx 450µA plus 0.4V x 1mA. Package theta
J-A is about 150°C/W, so with VCC= 5V and no copper
PC board heat-sinking, the resulting temperature rise
is:
dT = 2.7mW x 150°C/W = 0.4°C
Even with these contrived circumstances, it is difficult
to introduce significant self-heating errors.
ADC Noise Filtering

The ADC is an integrating type with inherently good
noise rejection, especially of low-frequency signals
such as 60Hz/120Hz power-supply hum. Micropower
operation places constraints on high-frequency noise
rejection; therefore, careful PC board layout and proper
external noise filtering are required for high-accuracy
remote measurements in electrically noisy environ-
ments.
High-frequency EMI is best filtered at DXP and DXN
with an external 2200pF capacitor. This value can be
increased to about 3300pF (max), including cable
capacitance. Higher capacitance than 3300pF intro-
duces errors due to the rise time of the switched cur-
rent source.
Nearly all noise sources tested cause the ADC measure-
ments to be higher than the actual temperature, typically
by +1°C to +10°C, depending on the frequency and
amplitude (see Typical Operating Characteristics).
MAX161
Remote/Local Temperature Sensor
with SMBus Serial Interface
Table 1. Remote-Sensor Transistor
Manufacturers
PC Board LayoutPlace the MAX1617 as close as practical to the
remote diode. In a noisy environment, such as a
computer motherboard, this distance can be 4 in. to
8 in. (typical) or more as long as the worst noise
sources (such as CRTs, clock generators, memory
buses, and ISA/PCI buses) are avoided.Do not route the DXP–DXN lines next to the deflec-
tion coils of a CRT. Also, do not route the traces
across a fast memory bus, which can easily intro-
duce +30°C error, even with good filtering.
Otherwise, most noise sources are fairly benign.Route the DXP and DXN traces in parallel and in
close proximity to each other, away from any high-
voltage traces such as +12VDC. Leakage currents
from PC board contamination must be dealt with
carefully, since a 20MΩleakage path from DXP to
ground causes about +1°C error.Connect guard traces to GND on either side of the
DXP–DXN traces (Figure 2). With guard traces in
place, routing near high-voltage traces is no longer
an issue. Route through as few vias and crossunders as possi-
ble to minimize copper/solder thermocouple effects. When introducing a thermocouple, make sure that
both the DXP and the DXN paths have matching
thermocouples. In general, PC board-induced ther-
mocouples are not a serious problem. A copper-sol-
der thermocouple exhibits 3µV/°C, and it takes
about 200µV of voltage error at DXP–DXN to cause
a +1°C measurement error. So, most parasitic ther-
mocouple errors are swamped out. Use wide traces. Narrow ones are more inductive
and tend to pick up radiated noise. The 10 mil
widths and spacings recommended in Figure 2
aren’t absolutely necessary (as they offer only a
minor improvement in leakage and noise), but try to
use them where practical.Keep in mind that copper can’t be used as an EMI
shield, and only ferrous materials such as steel work
well. Placing a copper ground plane between the
DXP-DXN traces and traces carrying high-frequency
noise signals does not help reduce EMI.
PC Board Layout Checklist
Place the MAX1617 close to a remote diode.Keep traces away from high voltages (+12V bus).Keep traces away from fast data buses and CRTs.Use recommended trace widths and spacings.Place a ground plane under the traces. Use guard traces flanking DXP and DXN and con-
necting to GND. Place the noise filter and the 0.1µF VCCbypass
capacitors close to the MAX1617.Add a 200Ωresistor in series with VCC for best
noise filtering (see Typical Operating Circuit).
Twisted Pair and Shielded Cables

For remote-sensor distances longer than 8 in., or in par-
ticularly noisy environments, a twisted pair is recom-
mended. Its practical length is 6 feet to 12 feet (typical)
before noise becomes a problem, as tested in a noisy
electronics laboratory. For longer distances, the best
solution is a shielded twisted pair like that used for audio
microphones. For example, Belden #8451 works well for
distances up to 100 feet in a noisy environment. Connect
the twisted pair to DXP and DXN and the shield to GND,
and leave the shield’s remote end unterminated.
Excess capacitance at DX_ limits practical remote sen-
sor distances (see Typical Operating Characteristics).
For very long cable runs, the cable’s parasitic capaci-
tance often provides noise filtering, so the 2200pF
capacitor can often be removed or reduced in value.
Cable resistance also affects remote-sensor accuracy;series resistance introduces about +1/2°C error.
Low-Power Standby Mode

Standby mode disables the ADC and reduces the sup-
ply-current drain to less than 10µA. Enter standby
mode by forcing the STBYpin low or via the RUN/STOP
bit in the configuration byte register. Hardware and
software standby modes behave almost identically: all
data is retained in memory, and the SMB interface is
alive and listening for reads and writes. The only differ-
ence is that in hardware standby mode, the one-shot
command does not initiate a conversion.
Standby mode is not a shutdown mode. With activity on
the SMBus, extra supply current is drawn (see Typical
Operating Characteristics). In software standby mode,
MAX161
Remote/Local Temperature Sensor
with SMBus Serial Interface

Figure 2. Recommended DXP/DXN PC Traces
the MAX1617 can be forced to perform A/D conversions
via the one-shot command, despite the RUN/STOP bit
being high.
Activate hardware standby mode by forcing the STBY
pin low. In a notebook computer, this line may be con-
nected to the system SUSTAT# suspend-state signal.
The STBYpin low state overrides any software conversion
command. If a hardware or software 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 either temperature reading register. The previ-
ous data is not changed and remains available.
Supply-current drain during the 125ms conversion peri-
od is always about 450µA. Slowing down the conver-
sion rate reduces the average supply current (see
Typical Operating Characteristics). In between conver-
sions, the instantaneous supply current is about 25µA
due to the current consumed by the conversion rate
timer. In standby mode, supply current drops to about
3µA. At very low supply voltages (under the power-on-
reset threshold), the supply current is higher due to the
address pin bias currents. It can be as high as 100µA,
depending on ADD0 and ADD1 settings.
SMBus Digital Interface

From a software perspective, the MAX1617 appears as a
set of byte-wide registers that contain temperature data,
alarm threshold values, or control bits. A standard
SMBus 2-wire serial interface is used to read tempera-
ture data and write control bits and alarm threshold data.
Each A/D channel within the device responds to the
same SMBus slave address for normal reads and writes.
The MAX1617 employs four standard SMBus protocols:
Write Byte, Read Byte, Send Byte, and Receive Byte
(Figure 3). The shorter Receive Byte protocol allows
quicker transfers, provided that the correct data register
was previously selected by a Read Byte instruction. Use
caution with the shorter protocols in multi-master systems,
since a second master could overwrite the command
byte without informing the first master.
The temperature data format is 7 bits plus sign in twos-com-
plement form for each channel, with each data bit repre-
senting 1°C (Table 2), transmitted MSB first. Measurements
are offset by +1/2°C to minimize internal rounding errors; for
example, +99.6°C is reported as +100°C.
MAX161
Remote/Local Temperature Sensor
with SMBus Serial Interface

Figure 3. SMBus Protocols
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