MAX1617AMEE ,Remote/Local Temperature Sensor with SMBus Serial InterfaceFeaturesThe MAX1617A (patents pending) is a precise digital ther-' Two Channels: Measures Both Remo ..
MAX1617AMEE+ ,Remote/Local Temperature Sensor with SMBus Serial InterfaceFeaturesThe MAX1617A is a precise digital thermometer that♦ Two Channels: Measures Both Remote and ..
MAX1617AMEE+T ,Remote/Local Temperature Sensor with SMBus Serial InterfaceELECTRICAL CHARACTERISTICS (continued)(V = +3.3V, T = 0°C to +85°C, unless otherwise noted.) (Note ..
MAX1617AMEE-T ,Remote/Local Temperature Sensor with SMBus Serial InterfaceEVALUATION KIT AVAILABLE MAX1617ARemote/Local Temperature Sensor with SMBus Serial Interface_______ ..
MAX1617AMEE-T ,Remote/Local Temperature Sensor with SMBus Serial InterfaceGeneral Description ________
MAX1617MEE ,Remote/Local Temperature Sensor with SMBus Serial InterfaceFeaturesThe MAX1617 (patents pending) is a precise digital' Two Channels: Measures Both Remote and ..
MAX4329ESD ,Single/Dual/Quad / Low-Cost / SOT23 / Low-Power / Rail-to-Rail I/O Op AmpsApplications6 2DOUT AINMAX4322SERIALPin Configurations appear at end of data sheet.INTERFACE8 4SCLK ..
MAX4329ESD+ ,Single/Dual/Quad, Low-Cost, UCSP/SOT23, Low-Power, Rail-to-Rail I/O Op AmpsELECTRICAL CHARACTERISTICS—T = +25°C A(V = 5.0V, V = 0V, V = 0V, V = V /2, SHDN = V R connected to ..
MAX432CPA ,【15V Chopper-Stabilized Operational Amplifierapplications.
They offer input offset and drift specifications superior to
previous "precision" b ..
MAX4330EUK ,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 ..
MAX4330EUK+T ,Single/Dual/Quad, Low-Power, Single-Supply, Rail-to-Rail I/O Op Amps with ShutdownMAX4330–MAX433419-1192; Rev 3; 2/98Single/Dual/Quad, Low -Pow er, Single-Supply,Rail-to-Rail I/O Op ..
MAX4331ESA ,Single/Dual/Quad / Low-Power / Single-Supply / Rail-to-Rail I/O Op Amps with ShutdownMAX4330–MAX433419-1192; Rev 3; 2/98Single/Dual/Quad, Low-Power, Single-Supply,Rail-to-Rail I/O Op A ..
MAX1617AMEE
Remote/Local Temperature Sensor with SMBus Serial Interface
________________General DescriptionThe MAX1617A (patents pending) is a precise digital ther-
mometer 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 conventional
thermistors or thermocouples. Remote accuracy 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-connected 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
two’s complement format. Measurements can be done
automatically and autonomously, with the conversion 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 MAX1617A is nearly identical to the popular MAX1617,
but has improved SMBus timing specifications, improved
bus collision immunity, software manufacturer and device
identification available via the serial interface, and a power-
on reset function that can force a reset of the slave address
via the serial interface.
________________________ApplicationsDesktop and NotebookCentral Office
ComputersTelecom Equipment
Smart Battery PacksTest and Measurement
LAN ServersMultichip Modules
Industrial Controls
____________________________FeaturesTwo Channels: Measures Both Remote and Local
TemperaturesNo Calibration RequiredSMBus 2-Wire Serial InterfaceProgrammable Under/Overtemperature AlarmsSupports SMBus Alert ResponseSupports Manufacturer and Device ID CodesAccuracy
±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 Configurationypical Operating CircuitSMBus is a registered trademark of Intel Corp.
*U.S. and foreign patents pending.
†Patents Pending
MAX1617A
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
MAX1617A
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.)
MAX1617A
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 MAX1617A device temper-
ature 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
(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.
MAX1617A
Remote/Local Temperature Sensor
with SMBus Serial Interface
____________________________Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
Rail-to Rail is a registered trademark of Nippon Motorola, Ltd.
MAX1617A
Remote/Local Temperature Sensor
with SMBus Serial Interface
Pin Description
General Description
The MAX1617A (patents pending) is a temperature
sensor 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 MAX1617A
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.
MAX1617A
Remote/Local Temperature Sensor
with SMBus Serial Interface
Figure 1. Functional Diagram
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.
A/D Conversion Sequence
If a Start command is written (or generated automatical-
ly in the free-running auto-convert mode), both channels
are converted, and the results of both measurements
are available after the end of conversion. A BUSY status
bit in the status byte shows that the device is actually
performing a new conversion; however, 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 MAX1617A 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 consistent
VBE characteristics.
For heatsink 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 MAX1617A’s
effective accuracy. The thermal time constant of the
QSOP-16 package is about 140sec in still air. For the
MAX1617A 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 VCC·450µA plus 0.4V ·1mA. Package theta
J-A is about 150°C/W, so with VCC= 5V and no copper
PC board heatsinking, the resulting temperature rise is:
dT = 2.7mW ·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).
MAX1617A
Remote/Local Temperature Sensor
with SMBus Serial Interface
Table 1. Remote-Sensor Transistor
Manufacturers
Note: Transistors must be diode-connected (base shorted to
collector).
PC Board LayoutPlace the MAX1617A 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 ChecklistPlace the MAX1617A 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 MAX1617A.Add a 200Ωresistor in series with VCCfor 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, the 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,
MAX1617A
Remote/Local Temperature Sensor
with SMBus Serial Interface
Figure 2. Recommended DXP/DXN PC Traces
