MAX1619MEE ,Remote/Local Temperature Sensor with Dual- Alarm Outputs and SMBus Serial InterfaceFeaturesThe MAX1619 is a precise digital thermometer that reports' Two Channels Measure Both Remote ..
MAX1619MEE+ ,Remote/Local Temperature Sensor with Dual Alarm Outputs and SMBus Serial InterfaceApplicationsPART TEMP. RANGE PIN-PACKAGEDesktop and Notebook Central Office Computers Telecom Equip ..
MAX1619MEE+ ,Remote/Local Temperature Sensor with Dual Alarm Outputs and SMBus Serial InterfaceFeaturesThe MAX1619 is a precise digital thermometer that reports♦ Two Channels Measure Both Remote ..
MAX161AEPI+ ,CMOS, 20µs, 8-Bit, 8-Channel Data Acquisition SystemFeatures
. Fast Conversion Tlme: 20psec (MAX161)
. No Missing Codes Over Temperature
. On ..
MAX161BCWI ,CMOS 8-Bit 8Channel Data Acquisition SystemApplications
Digital Signal Processing
Data Loggers
Automatic Test Equipment
Robotics
Pr ..
MAX161BCWI+ ,CMOS, 20µs, 8-Bit, 8-Channel Data Acquisition SystemELECTRICAL CHARACTERISTICS
(VDD = +5V, VREF = -10V, TA = TMIN to TMAX, unless otherwise specifie ..
MAX4351ESA ,Ultra-Small, Low-Cost, 210MHz, Dual-Supply Op Amps with Rail-to-Rail OutputsApplicationsSet-Top BoxesSurveillance Video SystemsVideo Line DriversOrdering InformationAnalog-to- ..
MAX4351ESA+ ,Ultra-Small, Low-Cost, 210MHz, Dual-Supply Op Amps with Rail-to-Rail OutputsELECTRICAL CHARACTERISTICS (V = +5V, V = -5V, R = to 0V, V = 0, T = T to T , unless otherwise noted ..
MAX4352EXK-T ,Low-Cost / +3V/+5V / 620A / 200MHz / Single-Supply Op Amps with Rail-to-Rail OutputsApplicationsMAX4352EXK-T -40°C to +85°C 5 SC70-5 ABJMAX4352EUK-T -40°C to +85°C 5 SOT23-5 ADOWTypic ..
MAX4356ECD+ ,16 x 16 Nonblocking Video Crosspoint Switch with On-Screen Display Insertion and I/O BuffersFeaturesThe MAX4356 is a 16 ✕ 16 highly integrated video✕♦ 16 16 Nonblocking Matrix with Buffered I ..
MAX4356ECD+ ,16 x 16 Nonblocking Video Crosspoint Switch with On-Screen Display Insertion and I/O BuffersApplicationsSecurity Systems Functional DiagramVideo RoutingOSDFILL1Video-on-Demand SystemsOSDFILL0 ..
MAX4357ECD+D ,32 x 16 Nonblocking Video Crosspoint Switch with I/O BuffersApplicationsMAX4357ECD -40°C to +85°C 128 TQFPSecurity SystemsPin Configuration appears at end of d ..
MAX1619MEE
Remote/Local Temperature Sensor with Dual- Alarm Outputs and SMBus Serial Interface
________________General DescriptionThe MAX1619 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 transis-
tor—typically a low-cost, easily mounted 2N3904 NPN
type—that replaces conventional thermistors or thermo-
couples. 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 MAX1619 is nearly identical to the popular MAX1617A,
with the additional feature of an overtemperature alarm out-
put (OVERT) that responds to the remote temperature; this
is optimal for fan control.
________________________ApplicationsDesktop and NotebookCentral Office
ComputersTelecom Equipment
Smart Battery PacksTest and Measurement
LAN ServersMultichip Modules
Industrial Controls
____________________________FeaturesTwo Channels Measure Both Remote and Local
TemperaturesNo Calibration RequiredSMBus 2-Wire Serial InterfaceProgrammable Under/Overtemperature AlarmsOVERT
Output for Fan ControlSupports 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 RangeWrite-Once ProtectionSmall 16-Pin QSOP Package
MAX1619
Remote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
___________________Pin Configurationypical Operating Circuit19-1483; Rev 0; 4/99
SMBus is a registered trademark of Intel Corp.
MAX1619
Remote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC= +3.3V, TA
= 0°C to +85°C, configuration byte = XCh, 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, OVERT, STBYto GND............................................................-0.3V to +6V
SMBDATA, ALERT,OVERTCurrent....................-1mA to +50mA
DXN Current.......................................................................±1mA
ESD Protection (all 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 +150°C
Lead Temperature (soldering, 10sec).............................+300°C
MAX1619
Remote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
ELECTRICAL CHARACTERISTICS (continued)(VCC= +3.3V, TA
= 0°C to +85°C, configuration byte = XCh, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS (VCC= +3.3V, TA
= -55°C to +125°C, configuration byte = XCh, unless otherwise noted.) (Note 4)
__________________________________________Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
MAX1619
Remote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
ELECTRICAL CHARACTERISTICS (continued)
(VCC= +3.3V, TA= -55°C to +125°C, configuration byte = XCh, unless otherwise noted.) (Note 4)
Note 1:Guaranteed but not 100% tested.
Note 2:Quantization error is not included in specifications for temperature accuracy. For example, if the MAX1619 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
(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:Specifications from -55°C to +125°C are guaranteed by design, not production tested.
Note 5: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 6: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.
MAX1619
Remote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX1619
Remote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
Pin Description
Detailed Description
The MAX1619 is a temperature sensor designed to work
in conjunction with an external microcontroller (µC) or
other intelligence in thermostatic, process-control, or
monitoring applications. The µC is typically a power-
management or keyboard controller, generating SMBus
serial commands either by “bit-banging” general-pur-
pose input/output (GPIO) pins or through a dedicated
SMBus interface block.
Essentially an 8-bit serial analog-to-digital converter
(ADC) with a sophisticated front end, the MAX1619
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 (local and remote). The remote
temperature data is automatically compared with data
previously stored in four temperature-alarm threshold
registers. One pair of alarm-threshold registers is used
to provide hysteretic fan control; the other pair is used
for alarm interrupt. The local temperature data is avail-
able for monitoring.
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.
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.
MAX1619
Remote/Local Temperature Sensor with Dual-
Alarm Outputs and 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 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 the devices list-
ed in Table 1. The MAX1619 can also directly measure
the die temperature of CPUs and other integrated cir-
cuits 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
temperature. Large power transistors don’t work. 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
VBEcharacteristics.
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 MAX1619’s
effective accuracy. The thermal time constant of the
QSOP-16 package is about 4sec in still air. To settle to
within +1°C after a sudden +100°C change, the
MAX1619 junction temperature requires about five time
constants. The use of smaller packages for remote sen-
sors, such as SOT23s, improves the situation. Take
care to account for thermal gradients between the heat
source and the sensor, and ensure that stray air cur-
rents 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 ALERTand OVERToutputs. For example, at
an 8Hz rate and with ALERTand OVERTeach sinking
1mA, the typical power dissipation is:
(VCC)(450µA) + 2(0.4V)(1mA)
Package qJAis about 120°C/W, so with VCC= 5V and
no copper PC board heatsinking, the resulting tempera-
ture rise is:
ΔT = 3.1mW(120°C/W) = 0.36°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 opera-
tion 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 environments.
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. Capacitance higher 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).
MAX1619
Remote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
Table 1. Remote-Sensor Transistor
Manufacturers
Note:Transistors must be diode-connected (base shorted to
collector).
PC Board LayoutPlace the MAX1619 as close as practical to the
remote diode. In a noisy environment, such as a
computer motherboard, this distance can be 4 inch-
es to 8 inches (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 10MΩleakage 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 MAX1619 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 MAX1619.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 inches, or in
particularly 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
in a noisy environment for distances up to 100 feet.
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 3µA (typical). 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 difference 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,
MAX1619
Remote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
Figure 2. Recommended DXP/DXN PC Traces
the MAX1619 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 conver-
sion cycle is truncated, and the data from that conversion
is not latched into either temperature reading register.
The previous data is not changed and remains available.
The OVERToutput continues to function in both hard-
ware and software standby modes. If the overtemp lim-
its are adjusted while in standby mode, the digital
comparator checks the new values and puts the OVERT
pin in the correct state based on the last valid ADC con-
version. The last valid ADC conversion may include a
conversion performed using the one-shot command.
Supply-current drain during the 125ms conversion peri-
od is always about 450µA. Slowing down the conversion
rate reduces the average supply current (see Typical
Operating Characteristics). Between conversions, 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 MAX1619 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 MAX1619 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 sys-
MAX1619
Remote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
