MAX6657MSA+ ,±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature AlarmsELECTRICAL CHARACTERISTICS(V = +3.0V to +5.5V, T = 0°C to +125°C, unless otherwise specified. Typic ..
MAX6657MSA+T ,±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature AlarmsFeaturesThe MAX6657/MAX6658/MAX6659 are precise, two- ♦ Dual Channel Measures Remote and Localchann ..
MAX6657YMSA+ ,±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature AlarmsApplications ating temperature range.+Denotes a lead(Pb)-free/RoHS-compliant package.Desktop Comput ..
MAX6658MSA ,1C / SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature AlarmsMAX6657/MAX6658/MAX665919-2034; Rev 2; 3/02±1°C, SMBus-Compatible Remote/Local TemperatureSensors w ..
MAX6659MEE ,1C / SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature AlarmsFeaturesThe MAX6657/MAX6658/MAX6659 are precise, two- Dual Channel: Measures Remote and Localchann ..
MAX665CPA ,8V CMOS Switched-Capacitor Voltage ConverterFeatures
. 0.65V Loss at 100mA Load
. 6.59 Output Impedance
. Pln-Compatlble High-Current ICL766 ..
MB3763 ,Bidirectional Motor DriverFEATURES• Motor Drive Current: 150 mA maximum (DC)300 mA maximum (tON = 1 s, Duty = 50 %)• Wide Pow ..
MB3763P ,Bidirectional Motor DriverBLOCK DIAGRAMA-VCC B-VCCInputLogicA-OUT B-OUTA-IN GND B-IN2MB3763nnnn ABSOLUTE MAXIMUM RATINGS(Ta = ..
MB3763PF ,Bidirectional Motor DriverFEATURES• Motor Drive Current: 150 mA maximum (DC)300 mA maximum (tON = 1 s, Duty = 50 %)• Wide Pow ..
MB3769A ,SWITCHING REGULATOR CONTROLLERFUJITSU SEMICONDUCTORDS04-27202-3EDATA SHEETASSPSWITCHING REGULATORCONTROLLERMB3769AThe Fujitsu MB3 ..
MB3769A. ,SWITCHING REGULATOR CONTROLLERFUJITSU SEMICONDUCTORDS04-27202-3EDATA SHEETASSPSWITCHING REGULATORCONTROLLERMB3769AThe Fujitsu MB3 ..
MB3771 ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-8EDATA SHEETASSP For power supply
MAX6657MSA+-MAX6657MSA+T-MAX6657YMSA+
±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms
General DescriptionThe MAX6657/MAX6658/MAX6659 are precise, two-
channel digital temperature sensors. Each accurately
measures the temperature of its own die and one
remote PN junction, and reports the temperature in digi-
tal form on a 2-wire serial interface. The remote junction
can be a diode-connected transistor like the low-cost
NPN type 2N3904 or 2N3906 PNP type. The remote
junction can also be a common-collector PNP, such as
a substrate PNP of a microprocessor.
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 MAX6657/MAX6658/
MAX6659 can function autonomously with a program-
mable conversion rate, which allows the control of sup-
ply current and temperature update rate to match
system needs. For conversion rates of 4Hz or less, the
temperature is represented in extended mode as 10
bits + sign with a resolution of 0.125°C. When the con-
version rate is faster than 4Hz, output data is 7 bits +
sign with a resolution of 1°C. The MAX6657/
MAX6658/MAX6659 also include an SMBus timeout
feature to enhance system reliability.
Remote accuracy is ±1°C between +60°C and +100°C
with no calibration needed. The MAX6657 measures
temperatures from 0°C to +125°C and the MAX6658/
MAX6659 from -55°C to +125°C. The MAX6659 has the
added benefit of being able to select one of three
addresses through an address pin, and a second over-
temperature alarm pin for greater system reliability.
ApplicationsDesktop ComputersWorkstations
Notebook Computers
Servers
FeaturesDual Channel Measures Remote and Local
Temperature11-Bit, +0.125°C ResolutionHigh Accuracy ±1°C (max) from +60°C to +100°C
(Remote)No Calibration RequiredProgrammable Under/Overtemperature AlarmsProgrammable Conversion Rate
(0.0625Hz to 16Hz)SMBus/I2C-Compatible InterfaceTwo Alarm Outputs: ALERTand OVERT1
(MAX6657 and MAX6658)Three Alarm Outputs: ALERT, OVERT1,
and OVERT2(MAX6659)Compatible with 65nm Process Technology
(Y Versions)
MAX6657/MAX6658/MAX6659
±1°C, SMBus-Compatible Remote/Local Temperature
Sensorswith Overtemperature Alarms19-2034; Rev 5; 10/10
Ordering Information
PARTMEASURED TEMP
RANGEPIN-PACKAGE
MAX6657MSA0°C to +125°C8 SO
MAX6657MSA+0°C to +125°C8 SO
MAX6657MSA-T0°C to +125°C8 SO
MAX6657MSA+T0°C to +125°C8 SO
MAX6657YMSA+0°C to +125°C8 SO
MAX6657YMSA+T0°C to +125°C8 SO
VCCN.C.
STBY
SMBCLK
N.C.
SMBDATA
N.C.
OVERT2
ALERT
TOP VIEW
MAX6659
N.C.
DXP
OVERT1
DXN
ADD
GND
GND
ALERT
GNDOVERT1
SMBCLK
SMBDATADXP
DXN
VCC
MAX6657
MAX6658
Pin Configurations
Typical Operating Circuit appears at the end of the data
sheet.
Ordering Information continued at end of data sheet.
Note: All devices are specified over the -55°C to +125°C oper-ating temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
MAX6657/MAX6658/MAX6659
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.
(All voltages referenced to GND.)
VCC..........................................................................-0.3V to +6V
DXP ............................................................-0.3V to (VCC+ 0.3V)
DXN ......................................................................-0.3V to +0.8V
SMBCLK, SMBDATA, ALERT, OVERT1,
OVERT2..............................................................-0.3V to +6V
SMBDATA, ALERT, OVERT1, OVERT2
Current ..........................................................-1mA to +50mA
DXN Current ......................................................................±1mA
Continuous Power Dissipation (TA= +70°C)
8-Pin SO (derate 5.9mW/°C above +70°C) .................471mW
16-Pin QSOP (derate 8.3mW/°C above +70°C) ..........664mW
Junction Temperature .....................................................+150°C
Storage Temperature Range ............................-65°C to +150°C
Lead Temperature (soldering, 10s) ................................+300°C
Soldering Temperature (reflow)
Lead(Pb)-free ..............................................................+260°C
Containing lead(Pb) ....................................................+240°C
ELECTRICAL CHARACTERISTICS(VCC= +3.0V to +5.5V, TA= 0°C to +125°C, unless otherwise specified. Typical values are at VCC= +3.3V and TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS1°CTemperature Resolution,
Legacy Mode8Bits
0.125°CTemperature Resolution,
Extended Mode11Bits
TRJ = +60°C to +100°C, VCC = +3.3V
(Note 1)-1.0+1.0
TRJ = 0°C to +100°C, VCC = +3.3V (Note 1)-3.0+3.0
Remote Temperature Error
(MAX6657, MAX6657Y)
TRJ = 0°C to +125°C, VCC = +3.3V (Note 1)-5.0+5.0
TA = +60°C to +100°C, VCC = +3.3V-2.0+2.0
TA = 0°C to +100°C, VCC = +3.3V-3.0+3.0Local Temperature Error
(MAX6657)TA = 0°C to +125°C, VCC = +3.3V-5.0+5.0
TRJ = +60°C to +100°C, VCC = +3.3V
(Note 1)-1.01.0
TRJ = 0°C to +100°C, VCC = +3.3V (Note 1)-3.03.0
Remote Temperature Error
(MAX6658/MAX6659/
MAX6658Y/MAX6659Y)
TRJ = -55°C to +125°C, VCC = +3.3V (Note 1)-5.0+5.0
TA = +60°C to +100°C, VCC = +3.3V-2.0+2.0
TA = 0°C to +100°C, VCC = +3.3V-3.0+3.0Local Temperature Error
(MAX6658/MAX6659)
TA = -55°C to +125°C, VCC = +3.3V (Note 2)-5.0+5.0
TA = +60°C to +100°C, VCC = +3.3V-3.8
TA = 0°C to +100°C, VCC = +3.3V-4.0Local Temperature Error
(MAX665_Y)
TA = 0°C to +125°C, VCC = +3.3V-4.4
Line Regulation3.0V ≤ VCC ≤ 5.5V0.20.6m°C/V
Supply Voltage RangeVCC3.05.5V
Undervoltage Lockout ThresholdUVLOFalling edge of VCC disables ADC2.602.802.95V
Undervoltage Lockout Hysteresis90mV
Power-On Reset (POR) ThresholdVCC, falling edge1.52.02.5V
POR Threshold Hysteresis90mV
Standby Supply CurrentSMBus static310µA
±1°C, SMBus-Compatible Remote/Local Temperature
Sensorswith Overtemperature Alarms
MAX6657/MAX6658/MAX6659
Note 1:TA= +25°C to +85°C.
Note 2:If both the local and the remote junction are below TA= -20°C, then VCC> 3.15V.
Note 3:For conversion rates of 4Hz or slower, the conversion time doubles.
Note 4:Timing specifications guaranteed by design.
Note 5:The serial interface resets when SMBCLK is low for more than tTIMEOUT.
ELECTRICAL CHARACTERISTICS (continued)(VCC= +3.0V to +5.5V, TA= 0°C to +125°C, unless otherwise specified. Typical values are at VCC= +3.3V and TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS0.25 conversions/s4070Average Operating Current2 conversions/s150250µA
Conversion TimetCONVFrom stop bit to conversion completed
(Note 4)95125156ms
Conversion Timing Error±25%
DXP and DXN Leakage CurrentIn standby mode100nA
High level80100120Remote-Diode Source CurrentIRJLow level81012µA
(ALERT, OVERT)VOL = 0.4V1Output Low Sink CurrentVOL = 0.6V6mA
Output High Leakage CurrentVOH = 5.5V1µA
SMBus-COMPATIBLE INTERFACE (SMBCLK, SMBDATA, STBY)Logic Input Low VoltageVIL0.8V
VCC = +3.0V2.2Logic Input High VoltageVIHVCC = +5.5V2.4V
Input Leakage CurrentILEAKVIN = VGND or VCC±1µA
Output Low Sink CurrentIOLVOL = 0.6V6mA
Input CapacitanceCIN5pF
SMBus-COMPATIBLE TIMING (Note 4)Serial-Clock FrequencyfSCL(Note 5)100kHz
Bus Free Time Between STOP
and START ConditiontBUF4.7µs
START Condition Setup Time4.7µs
Repeat START Condition Setup
TimetSU:STA90% to 90%50ns
START Condition Hold TimetHD:STA10% of SMBDATA to 90% of SMBCLK4µs
STOP Condition Setup TimetSU:STO90% of SMBCLK to 90% of SMBDATA4µs
Clock Low PeriodtLOW10% to 10%4.7µs
Clock High PeriodtHIGH90% to 90%4µs
Data Setup TimetHD:DAT(Note 6)0µs
Receive SCL/SDA Rise TimetR1µs
Receive SCL/SDA Fall TimetF300ns
Pulse Width of Spike SuppressedtSP050ns
SMBus TimeoutSMBDATA low period for interface reset253745ms
±1°C, SMBus-Compatible Remote/Local Temperature
Sensorswith Overtemperature Alarms
MAX6657/MAX6658/MAX6659
Typical Operating Characteristics(VCC= +3.3V, TA= +25°C, unless otherwise noted.)
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6657 toc01
SUPPLY VOLTAGE (V)
STANDBY SUPPLY CURRENT (
OPERATING SUPPLY CURRENT
vs. CONVERSION RATE
MAX6657 toc02
CONVERSION RATE (Hz)
OPERATING SUPPLY CURRENT (
8Hz AND 16Hz ARE 1°C RESOLUTION
MAX6659
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
MAX6657 toc03
TEMPERATURE (°C)
TEMPERATURE ERROR (
FAIRCHILD 2N3906
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX6657 toc04
TEMPERATURE (°C)
TEMPERATURE ERROR (
10k1M100k10M100M
TEMPERATURE ERROR vs.
POWER-SUPPLY NOISE FREQUENCYMAX6657 toc05
FREQUENCY (Hz)
TEMPERATURE ERROR (
VIN = SQUARE WAVE APPLIED TO VCC
WITH NO 0.1μF VCC CAPACITOR
0.01k100k1k10M1G
TEMPERATURE ERROR vs.
COMMON-MODE NOISE FREQUENCYMAX6657 toc06
FREQUENCY (Hz)
TEMPERATURE ERROR (
VIN = AC-COUPLED TO DXN
VIN = 100mVp-p
10k1M100k10M100M
TEMPERATURE ERROR vs.
DIFFERENTIAL-MODE NOISE FREQUENCYMAX6657 toc07
TEMPERATURE ERROR (
VIN = 10mVP-P SQUARE WAVE
APPLIED TO DXP-DXN
TEMPERATURE ERROR vs.
DXP-DXN CAPACITANCE
MAX6657 toc08
TEMPERATURE ERROR (
±1°C, SMBus-Compatible Remote/Local Temperature
Sensorswith Overtemperature Alarms
MAX6657/MAX6658/MAX6659
PIN
MAX6657
MAX6658MAX6659NAMEFUNCTIONVCC
Supply Voltage Input, +3V to +5.5V. Bypass to GND with a 0.1µF capacitor. A 200Ω
series resistor is recommended but not required for additional noise filtering. See
Typical Operating Circuit.3DXP
Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode
Channel. DO NOT LEAVE DXP UNCONNECTED; connect DXP to DXN if no remote
diode is used. Place a 2200pF capacitor between DXP and DXN for noise filtering.DXNCombined Remote-Diode Current Sink and A/D Negative Input. DXN is internally
biased to one diode drop above ground.OVERT1Overtemperature Active-Low Output, Open-Drain. Output is logic low only when
temperature is above the software programmed threshold.7, 8GNDGroundALERT
SMBus Alert (Interrupt) Active-Low Output, Open-Drain. Asserts when temperature
exceeds user-set limits (high or low temperature). Stays asserted until acknowledged
by either reading the Status register or by successfully responding to an Alert
Response address. See ALERT Interrupts.12SMBDATASMBus Serial-Data Input/Output, Open-Drain14SMBCLKSMBus Serial-Clock Input5ADDSMBus Address-Select Pin. The MAX6659 is set to one of three available addresses
(connect to VCC, GND, or leave open). See Slave Addresses section.
—10OVERT2Overtemperature Active-Low Output, Open-Drain. Output is logic low only when
temperature is above the software programmed threshold.
—15STBYHardware Standby Input. Temperature and comparison threshold data are retained in
standby mode. If STBY is low, the IC is put into standby mode.2, 11, 13, 16N.C.Not internally connected. Do not make connections to these pins.
Pin Description
±1°C, SMBus-Compatible Remote/Local Temperature
Sensorswith Overtemperature Alarms
MAX6657/MAX6658/MAX6659
Detailed DescriptionThe MAX6657/MAX6658/MAX6659 are temperature
sensors designed to work in conjunction with a micro-
processor or other intelligence in thermostatic,
process-control, or monitoring applications. Com-
munication with the MAX6657/MAX6658/MAX6659
occurs through the SMBus serial interface and dedicat-
ed alert pins. Two independent overtemperature alarms
(OVERT1and OVERT2) are asserted if their software
programmed temperature thresholds are exceeded.
OVERT1and OVERT2can be connected to fans, a sys-
tem shutdown, or other thermal management circuitry.
The MAX6657/MAX6658/MAX6659 convert tempera-
tures to digital data either at a programmed rate or a
single conversion. Conversions have a 0.125°C resolu-
tion (extended resolution) or 1°C resolution (legacy res-
olution). Extended resolution represents temperature as
10 bits + sign bit and is available for autonomous con-
versions that are 4Hz and slower and single-shot con-
versions. Legacy resolution represents temperature as
7 bits + sign bit and allows for faster autonomous con-
version rates of 8Hz and 16Hz.
ADC and MultiplexerThe averaging ADC integrates over a 60ms period
(each channel, typically, in the 7-bit + sign legacy
mode). Using an averaging ADC attains excellent noise
rejection.
The multiplexer automatically steers bias currents
through the remote and local diodes. The ADC and
associated circuitry measure each diode’s forward volt-
age and compute the temperature based on this volt-
age. If the remote channel is not used, connect DXP to
DXN. Do not leave DXP and DXN unconnected. When a
MUX
REMOTE
LOCAL
ADC
CONTROL
LOGIC
SMBus
READ
WRITE
ADDRESS
DECODERQ
DIODE
FAULT
DXP
DXN
(ADD)
SMBCLK
SMBDATA
REGISTER BANKCOMMAND BYTE
REMOTE TEMPERATURE
LOCAL TEMPERATURE
ALERT THRESHOLD
ALERT RESPONSE
ADDRESS
OVERT1 THRESHOLD
(OVERT2 THRESHOLD)
( ) ARE FOR MAX6659 ONLYMAX6659 ONLY
VCC
MAX6657
MAX6658
MAX6659
(STBY)
ALERT
OVERT1
(OVERT2)
Functional Diagram
±1°C, SMBus-Compatible Remote/Local Temperature
Sensorswith Overtemperature Alarms
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 differential 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 a remote temperature measurement.
Each time a conversion begins, whether initiated auto-
matically in the free-running autoconvert mode
(RUN/STOP = 0) or by writing a “one-shot” command,
both channels are converted, and the results of both
measurements are available after the end of conver-
sion. A BUSY status bit in the Status register shows that
the device is actually performing a new conversion. The
results of the previous conversion sequence are still
available when the ADC is busy.
Remote-Diode SelectionThe MAX6657/MAX6658/MAX6659 can directly mea-
sure the die temperature of CPUs and other ICs that
have on-board temperature-sensing diodes (see
Typical Operating Circuit) or they can measure the tem-
perature of a discrete diode-connected transistor. The
type of remote diode used is set by bit 5 of the
Configuration Byte. If bit 5 is set to zero, the remote
sensor is a diode-connected transistor, and if bit 5 is set
to 1, the remote sensor is a substrate or common collec-
tor PNP transistor. For best accuracy, the discrete tran-
sistor should be a small-signal device with its collector
and base connected together. Accuracy has been
experimentally verified for all the devices listed in Table1.
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, 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 speci-
fications for forward current gain (50 < β< 150, for
example) indicate that the manufacturer has good
process controls and that the devices have consistent
VBEcharacteristics.
Thermal Mass and Self-HeatingWhen sensing local temperature, these devices are
intended to measure the temperature of the PC board
to which they are soldered. The leads provide a good
thermal path between the PC board traces and the die.
Thermal conductivity between the die and the ambient
air is poor by comparison, making air temperature mea-
surements impractical. Because the thermal mass of
the PC board is far greater than that of the MAX6657/
MAX6658/MAX6659, the devices follow 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 sen-
sors, smaller packages (i.e., a SOT23) yield the best
thermal response times. Take care to account for ther-
mal 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 autoconverting at the
fastest rate and simultaneously sinking maximum cur-
rent at the ALERToutput. For example, with VCC=
+5.0V, a 16Hz conversion rate and ALERTsinking
1mA, the typical power dissipation is:
VCCx 450µA + 0.4V x 1mA = 2.65mW
θJ-Afor the 8-pin SO package is about +170°C/W, so
assuming no copper PC board heat sinking, the result-
ing temperature rise is:
∆T = 2.65mW x +170°C/W = +0.45°C
Even under these engineered circumstances, it is diffi-
cult to introduce significant self-heating errors.
ADC Noise FilteringThe integrating ADC used has good noise rejection for
low-frequency signals such as 60Hz/120Hz power-sup-
ply hum. In noisy environments, high-frequency noise
reduction is needed for high-accuracy remote mea-
MAX6657/MAX6658/MAX6659
MANUFACTURERMODEL NUMBERCentral Semiconductor (USA)CMPT3904
Fairchild Semiconductor (USA)2N3904, 2N3906
On Semiconductor (USA)2N3904, 2N3906
Rohm Semiconductor (USA)SST3904
Samsung (Korea)KST3904-TF
Siemens (Germany)SMBT3904
Zetex (England)FMMT3904CT-ND
Note:Transistors must be diode connected (base shorted to
collector).
Table 1. Remote-Sensor Transistor
±1°C, SMBus-Compatible Remote/Local Temperature
Sensorswith Overtemperature Alarms
MAX6657/MAX6658/MAX6659surements. The noise can be reduced with careful PC
board layout and proper external noise filtering.
High-frequency EMI is best filtered at DXP and DXN
with an external 2200pF capacitor. Larger capacitor
values can be used for added filtering, but do not
exceed 3300pF because it can introduce errors due to
the rise time of the switched current source.
PC Board LayoutFollow these guidelines to reduce the measurement
error of the temperature sensors:Place the MAX6657/MAX6658/MAX6659 as close
as is practical to the remote diode. In noisy environ-
ments, such as a computer motherboard, this dis-
tance can be 4in to 8in (typ). This length can be
increased if the worst noise sources are avoided.
Noise sources include CRTs, clock generators,
memory buses, and ISA/PCI buses.Do not route the DXP-DXN lines next to the deflec-
tion coils of a CRT. Also, do not route the traces
across fast digital signals, which can easily intro-
duce +30°C error, even with good filtering.Route the DXP and DXN traces in parallel and in
close proximity to each other, away from any higher
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. If high-voltage
traces are unavoidable, connect guard traces to GND
on either side of the DXP-DXN traces (Figure 1).Route through as few vias and crossunders as pos-
sible to minimize copper/solder thermocouple
effects.When introducing a thermocouple, make sure that
both the DXP and the DXN paths have matching
thermocouples. A copper-solder thermocouple
exhibits 3µV/°C, and it takes about 200µV of voltage
error at DXP-DXN to cause a +1°C measurement
error. Adding a few thermocouples causes a negli-
gible error.Use wide traces. Narrow traces are more inductive
and tend to pick up radiated noise. The 10mil widths
and spacings that are recommended in Figure 1 are
not absolutely necessary, as they offer only a minor
improvement in leakage and noise over narrow
traces. Use wider traces when practical.Add a 200Ωresistor in series with VCCfor best
noise filtering (see Typical Operating Circuit).
Twisted-Pair and Shielded CablesUse a twisted-pair cable to connect the remote sensor
for remote-sensor distances longer than 8in or in very
noisy environments. Twisted-pair cable lengths can be
between 6ft and 12ft before noise introduces excessive
errors. For longer distances, the best solution is a
shielded twisted pair like that used for audio micro-
phones. For example, Belden #8451 works well for dis-
tances up to 100ft in a noisy environment. At the
device, connect the twisted pair to DXP and DXN and
the shield to GND. Leave the shield unconnected at the
remote sensor.
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.
For every 1Ωof series resistance, the error is approxi-
mately +1/2°C.
Low-Power Standby ModeStandby mode reduces the supply current to less than
10µA by disabling the ADC. Enter hardware standby
(MAX6659 only) by forcing the STBYpin low, or enter
software standby by setting the RUN/STOP bit to 1 in
the Configuration Byte register. Hardware and software
standbys are very similar—all data is retained in memo-
ry,and the SMB interface is alive and listening for
SMBus commands. The only difference is that in soft-
ware standby mode, the one-shot command initiates a
conversion. With hardware standby, the one-shot com-
mand is ignored. Activity on the SMBus causes the
device to draw extra supply current.
Driving the STBYpin low overrides any software con-
version command. If a hardware or software standby
command is received while a conversion is in progress,
the conversion cycle is interrupted, and the tempera-
MINIMUM
10MILS
10MILS
10MILS
10MILS
GND
DXN
DXP
GND
Figure 1. Recommended DXP-DXN PC Traces
±1°C, SMBus-Compatible Remote/Local Temperature
Sensorswith Overtemperature Alarms
