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 ..
MAX161CMJI ,CMOS 8-Bit 8Channel Data Acquisition SystemFeatures
. Fast Conversion Tlme: 20psec (MAX161)
. No Missing Codes Over Temperature
. On ..
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 Packagemote/Local Temperature Sensor with Dua
Alarm Outputs and SMBus Serial InterfacMAX1619
SMBCLK
ADD0ADD1
VCCSTBY
GND
ALERT
SMBDATA
DXP
DXNINTERRUPT
TO μC
FAN
CONTROL
+3V TO +5.5V
200Ω0.1μF
CLOCK
10k EACH
DATA
2N39042200pF
OVERT
___________________Pin ConfigurationVCCN.C.
STBY
SMBCLK
N.C.
SMBDATA
ALERT
ADD0
OVERT
TOP VIEW
MAX1619
QSOPGND
DXP
ADD1
DXN
N.C.
GND
GND
Typical Operating Circuit19-1483; Rev 0; 4/99
PARTMAX1619MEE-55°C to +125°C
TEMP. RANGEPIN-PACKAGE16 QSOP
Ordering InformationSMBus is a registered trademark of Intel Corp.
mote/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
TA = +60°C to +100°C
Monotonicity guaranteed
ADD0, ADD1; momentary upon power-on reset
DXP forced to 1.5V
Logic inputs
forced to VCC
or GND
Auto-convert mode
From stop bit to conversion complete (both channels)
VCC, falling edge
TA = 0°C to +85°C
VCCinput, disables A/D conversion, rising edge
Autoconvert mode, average
measured over 4sec. Logic
inputs forced to VCCor GND.
CONDITIONS160Address Pin Bias Current0.7DXN Source Voltage81012100120Remote-Diode Source Current-2525Conversion Rate Timing Error94125156Conversion Time
Average Operating Supply Current2
Bits8Temperature Resolution (Note 1)
Standby Supply Current1050POR Threshold Hysteresis1.01.72.5Power-On Reset Threshold-33
Initial Temperature Error,
Local Diode (Note 2)3.05.5Supply Voltage Range2.602.802.95Undervoltage Lockout Threshold50Undervoltage Lockout Hysteresis
UNITSMINTYPMAXPARAMETERTR = +60°C to +100°C
TR = -55°C to +125°C (Note 4)3°C-55
Temperature Error, Remote Diode
(Notes 2, 3)
Including long-term drift-2.52.5°C-3.53.5
Temperature Error, Local Diode
(Notes 1, 2)
0.25 conv/sec
2.0 conv/sec
TA = +60°C to +100°C
TA = 0°C to +85°C
High level
Low level
ADC AND POWER SUPPLYSMBus static
Hardware or software standby,
SMBCLK at 10kHz
mote/Local Temperature Sensor with Dual-Alarm Outputs and SMBus Serial Interfac
ELECTRICAL CHARACTERISTICS (continued)(VCC= +3.3V, TA
= 0°C to +85°C, configuration byte = XCh, unless otherwise noted.) STBY, SMBCLK, SMBDATA; VCC= 3V to 5.5V
tHIGH, 90% to 90% points
tLOW, 10% to 10% points
(Note 5)
SMBCLK, SMBDATA
Logic inputs forced to VCCor GND
ALERT,OVERT,forced to 5.5V
STBY, SMBCLK, SMBDATA; VCC= 3V to 5.5V
ALERT,OVERT, SMBDATA forced to 0.4V
CONDITIONS4SMBCLK Clock High Time4.7SMBCLK Clock Low Time
kHzDC100SMBus Clock Frequency5SMBus Input Capacitance-11Logic Input Current1ALERT,OVERTOutput High
Leakage Current2.2Logic Input High Voltage0.8Logic Input Low Voltage6Logic Output Low Sink Current
UNITSMINTYPMAXPARAMETERtSU:DAT, 10% or 90% of SMBDATA to 10% of SMBCLK
tSU:STO, 90% of SMBCLK to 10% of SMBDATA
tHD:STA, 10% of SMBDATA to 90% of SMBCLK
tSU:STA, 90% to 90% points250SMBus Data Valid to SMBCLK
Rising-Edge Time4SMBus Stop-Condition Setup Time4SMBus Start-Condition Hold Time500SMBus Repeated Start-Condition
Setup Time4.7SMBus Start-Condition Setup Time
tHD:DAT(Note 6)μs0SMBus Data-Hold Time
Master clocking in dataμs1SMBCLK Falling Edge to SMBus
Data-Valid Time
SMBus INTERFACE
ELECTRICAL CHARACTERISTICS (VCC= +3.3V, TA
= -55°C to +125°C, configuration byte = XCh, unless otherwise noted.) (Note 4)
CONDITIONSMonotonicity guaranteed= +60°C to +100°C
Bits8Temperature Resolution (Note 1)2= +60°C to +100°C= -55°C to +125°C°C-33
Initial Temperature Error,
Local Diode (Note 2)3.05.5Supply Voltage Range
From stop bit to conversion complete (both channels)
Autoconvert mode94125156Conversion Time-2525Conversion Rate Timing Error3= -55°C to +125°C°C
UNITSMINTYPMAX5
PARAMETERTemperature Error, Remote Diode
(Notes 2, 3)
ADC AND POWER SUPPLY
5k500k50k5M50050M
TEMPERATURE ERROR vs.
POWER-SUPPLY NOISE FREQUENCYAX1619-03
FREQUENCY (Hz)
(°
VIN = SQUARE WAVE APPLIED TO
VCC WITH NO 0.1μF VCC CAPACITOR
VIN = 250mVp-p
REMOTE DIODE
VIN = 100mVp-p
LOCAL DIODE
VIN = 100mVp-p
REMOTE DIODE
TEMPERATURE ERROR
vs. PC BOARD RESISTANCE
X1619-01
LEAKAGE RESISTANCE (MΩ)
(°10100
PATH = DXP TO GND
PATH = DXP TO VCC (5V)
TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
X1619-02
TEMPERATURE (°C)
(°
MOTOROLA MMBT3904
ZETEX FMMT3904
RANDOM
SAMPLES
__________________________________________Typical Operating Characteristics(TA = +25°C, unless otherwise noted.)
mote/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.
CONDITIONSUNITSMINTYPMAXPARAMETERSTBY, SMBCLK, SMBDATA2.2Logic Input High VoltageV2.4
STBY, SMBCLK, SMBDATA; VCC= 3V to 5.5VV0.8Logic Input Low Voltage
ALERT,OVERTforced to 5.5VμA1ALERT, OVERTOutput High
Leakage Current
Logic inputs forced to VCCor GNDμA-22Logic Input Current
VCC= 3V
VCC= 5.5V
ALERT,OVERT, SMBDATA forced to 0.4VmA6Logic Output Low Sink Current
SMBus INTERFACE
mote/Local Temperature Sensor with DuaAlarm Outputs and SMBus Serial Interfac
TEMPERATURE ERROR vs.
COMMON-MODE NOISE FREQUENCYAX1619-04
FREQUENCY (MHz)
(°C
VIN = 100mVp-p
VIN = SQUARE WAVE
AC-COUPLED TO DXN
VIN = 50mVp-p
VIN = 25mVp-p40608020100
TEMPERATURE ERROR vs.
DXP–DXN CAPACITANCEAX1619-07
DXP–DXN CAPACITANCE (nF)
(°
VCC = 5V
OPERATING SUPPLY CURRENT
vs. CONVERSION RATE
AX1619-10
CONVERSION RATE (Hz)
(μ
VCC = 5V
AVERAGED MEASUREMENTS100101000
STANDBY SUPPLY CURRENT
vs. CLOCK FREQUENCYAX1619-08
SMBCLK FREQUENCY (kHz)
(μ
VCC = 5V
VCC = 3.3V
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
AX1619-09
SUPPLY VOLTAGE (V)
(μ
ADD0, ADD1 = GND
ADD0, ADD1 = HIGH-Z
1258 042610
INTERNAL DIODE
RESPONSE TO THERMAL SHOCKX1619-11
TIME (sec)
(°
16-QSOP IMMERSED
IN +115°C FLUORINERT BATH
Typical Operating Characteristics (continue(TA = +25°C, unless otherwise noted.)
mote/Local Temperature Sensor with Dual-Alarm Outputs and SMBus Serial Interface
Pin Descriptiontailed DescriptionThe 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.
SMBus Serial-Data Input/Output, Open DrainSMBDATA12
SMBus Serial-Clock InputSMBCLK14
Hardware Standby Input. Temperature and comparison threshold data are retained in standby mode.
Low = standby mode, high = operate mode.STBY15
SMBus Address Select Pin (Table 8). ADD0 and ADD1 are sampled upon power-up. Excess capacitance
(>50pF) at the address pins when floating may cause address-recognition problems.ADD16
GroundGND7, 8
SMBus Slave Address Select PinADD010
SMBus Alert (interrupt) Output, Open DrainALERT11
Combined Current Sink and A/D Negative Input. DXN is normally internally biased to a diode voltage
above ground. DXN4
Combined Current Source and A/D Positive Input for Remote-Diode Channel. Do not leave DXP floating;
connect DXP to DXN if no remote diode is used. Place a 2200pF capacitor between DXP and DXN for
noise filtering.
DXP3
PINSupply Voltage Input, 3V to 5.5V. Bypass to GND with a 0.1μF capacitor. A 200Ωseries resistor is recom-
mended but not required for additional noise filtering.VCC1
FUNCTIONNAMEOvertemperature Alarm Output, Open Drain. This is an unlatched alarm output that responds only to the
remote diode temperature.OVERT9
Not internally connected. Connect to GND to act against leakage paths from VCCto DXP.GND2
No Connection. Not internally connected. May be used for PC board trace routing.N.C.5, 13,
mote/Local Temperature Sensor with Dual-Alarm Outputs and SMBus Serial InterfacFigure 1. Functional Diagram
(IN
) R
+--8R
A/D Conversion SequenceIf 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 SelectionTemperature 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-HeatingThermal 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 θJAis 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 FilteringThe 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).
mote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial InterfaceCMPT3904Central Semiconductor (USA)
MMBT3904Fairchild Semiconductor (USA)
SST3904Rohm Semiconductor (Japan)
FMMT3904CT-NDZetex (England)
MANUFACTURERMODEL NUMBERSMBT3904Siemens (Germany)
Table 1. Remote-Sensor Transistor
Manufacturers
Note:Transistors must be diode-connected (base shorted to
collector).
MMBT3904Motorola (USA)
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-uce +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).
isted 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 ModeStandby 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,
mote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial InterfacMINIMUM
10 MILS
10 MILS
10 MILS
10 MILS
GND
DXN
DXP
GND
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 InterfaceFrom 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-
mote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
ACK7 bits
ADDRESSACKWR8 bits
DATAACK8 bits
COMMAND
Write Byte Format
Read Byte Format
Send Byte FormatReceive Byte FormatSlave Address:
equivalent to chip-select
line of a 3-wire interface
Command Byte: selects
which register you are
writing to
Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
ACK7 bits
ADDRESSACKWRSACK8 bits
DATA7 bits
ADDRESSRD8 bits
///PSCOMMANDSlave Address:
equivalent to
chip-select line
Command Byte: selects
which register you are
reading from
Slave Address: repeated
due to change in data-
flow direction
Data Byte: reads from
the register set by the
command byte
ACK7 bits
ADDRESSWR8 bits
COMMANDACKPSACK7 bits
ADDRESSRD8 bits
DATA///PSCommand Byte: sends com-
mand with no data; usually
used for one-shot command
Data Byte: reads data from
the register commanded
by the last Read Byte or
Write Byte transmission;
also used for SMBus Alert
Response return address
S = Start conditionShaded = Slave transmission
P = Stop condition/// = Not acknowledged
