MAX6689UP9A+ ,7-Channel Precision Temperature MonitorApplicationsMAX6689EP9E+ 20 QSOP 1001 111 E20-1Desktop Computers MAX6689UP34+ 20 TSSOP 0011 010 U20 ..
MAX6689UP9A+T ,7-Channel Precision Temperature MonitorELECTRICAL CHARACTERISTICS(V = +3.0V to +5.5V, V = V , T = -40°C to +125°C, unless otherwise noted. ..
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MAX668EUB ,1.8V to 28V Input / PWM Step-Up Controllers in MAXFeaturesThe MAX668/MAX669 constant-frequency, pulse-width-' 1.8V Minimum Start-Up Voltage (MAX669)m ..
MAX668EUB ,1.8V to 28V Input / PWM Step-Up Controllers in MAXApplicationsoperates in PWM mode at medium and heavy loads forlowest noise and optimum efficiency, ..
MAX668EUB+ ,1.8V to 28V Input, PWM Step-Up Controllers in µMAXApplications100mV current-sense voltage as well as with Maxim’s proprietary Idle Mode™ control sche ..
MB3771PF ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
MB3771PF. ,Power Supply MonitorapplicationsBIPOLARPower Supply MonitorMB3771nnnn DESCRIPTIONThe Fujitsu MB3771 is designed to moni ..
MB3771PF-G-BND-JNE1 , ASSP For power supply applications BIPOLAR Power Supply Monitor
MB3771PS ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
MB3771PS ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
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MAX6689UP9A+-MAX6689UP9A+T
7-Channel Precision Temperature Monitor
General DescriptionThe MAX6689 precision multichannel temperature sen-
sor monitors its own temperature and the temperatures
of up to six external diode-connected transistors. All
temperature channels have programmable alert thresh-
olds. Channels 1, 4, 5, and 6 also have programmable
overtemperature thresholds. When the measured tem-
perature of a channel exceeds the respective thresh-
old, a status bit is set in one of the status registers. Two
open-drain outputs, OVERTand ALERT, assert corre-
sponding to these bits in the status register.
The 2-wire serial interface supports the standard system
management bus (SMBus™) protocols: write byte, read
byte, send byte, and receive byte for reading the tem-
perature data and programming the alarm thresholds.
The MAX6689 is specified for an operating temperature
range of -40°C to +125°C and is available in 20-pin
QSOP and TSSOP packages.
ApplicationsDesktop Computers
Notebook Computers
Workstations
Servers
FeaturesSix Thermal-Diode InputsLocal Temperature Sensor1°C Remote Temperature Accuracy (+60°C to +100°C)Temperature Monitoring Begins at POR for Fail-
Safe System ProtectionALERT
and OVERTOutputs for Interrupts,
Throttling, and ShutdownSTBY
Input for Hardware Standby ModeSmall, 20-Pin QSOP and TSSOP Packages2-Wire SMBus Interface
MAX6689
7-Channel Precision Temperature Monitor
Ordering InformationGND
SMBCLK
SMBDATA
DXN2
DXP2
DXN1
DXP1
VCC
N.C.
DXN4
DXP4
DXN3
DXP3
DXP6
DXN6DXN5
DXP5
MAX6689
ALERT
OVERT
STBY
2200pF
2200pF
2200pF
2200pF
2200pF
CPU
2200pF
GPU
0.1μF
TO SYSTEM
SHUTDOWN
INTERRUPT
TO μP
DATA
CLK
4.7kΩ
EACH
+3.3V
Typical Application Circuit19-0567; Rev 1; 8/07
PARTPIN-
PACKAGE
SLAVE
ADDRESS
PKG
CODEMAX6689EP34+20 QSOP0011 010E20-1
MAX6689EP38+20 QSOP0011 100E20-1
MAX6689EP9A+20 QSOP1001 101E20-1
MAX6689EP9E+20 QSOP1001 111E20-1
MAX6689UP34+20 TSSOP0011 010U20-2
MAX6689UP38+20 TSSOP0011 100U20-2
MAX6689UP9A+20 TSSOP1001 101U20-2
MAX6689UP9E+20 TSSOP1001 111U20-2
SMBus is a trademark of Intel Corp.
Note: All devices are specified over the -40°C to +125°Ctemperature range.
+Denotes lead-free package.
Pin Configuration appears at end of data sheet.
MAX6689
7-Channel Precision Temperature Monitor
ABSOLUTE MAXIMUM RATINGS
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.
VCC, SCK, SDA, ALERT, OVERT, STBYto GND .....-0.3V to +6V
DXP_ to GND..............................................-0.3V to (VCC+ 0.3V)
DXN_ to GND........................................................-0.3V to +0.8V
SDA, ALERT, OVERTCurrent.............................-1mA to +50mA
DXN Current.......................................................................±1mA
Continuous Power Dissipation (TA= +70°C)
20-Pin QSOP
(derate 9.1mW/°C above +70°C)..................................727.3mW
20-Pin TSSOP
(derate 11.0mW/°C above +70°C)..............................879.1mW
ESD Protection (all pins, Human Body Model)................±2000V
Operating Temperature Range.........................-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
ELECTRICAL CHARACTERISTICS
(VCC= +3.0V to +5.5V, VSTBY= VCC, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VCC= +3.3V and TA=
+25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Supply VoltageVCC3.05.5V
Software Standby Supply CurrentISSSMBus static30µA
Operating CurrentICCDuring conversion5001000µA
Channel 1 only11Temperature ResolutionOther diode channels8Bits
TA = TRJ = +60°C to +100°C-1.0+1.0
TA = TRJ = 0°C to +125°C-3.0+3.0Remote Temperature AccuracyVCC = 3.3V
DXN_ grounded,
TRJ = TA = 0°C to +85°C±2.5C
TA = +60°C to +100°C-3.3+0.7Local Temperature AccuracyVCC = 3.3VTA = 0°C to +125°C-5.0+1.0C
Supply Sensitivity of Temperature
Accuracy±0.2oC/V
Resistance cancellation off95125156Remote Channel 1 Conversion
TimetCONV1Resistance cancellation on190250312ms
Remote Channels 2 Through 6
Conversion TimetCONV_95125156ms
High level80100120Remote-Diode Source CurrentIRJLow level81012µA
Undervoltage-Lockout ThresholdUVLOFalling edge of VCC disables ADC2.302.802.95V
Undervoltage-Lockout Hysteresis90mV
Power-On Reset (POR) ThresholdVCC falling edge1.22.02.5V
POR Threshold Hysteresis90mV
ALERT, OVERT
ISINK = 1mA0.3Output Low VoltageVOLISINK = 6mA0.5V
Output Leakage Current1µA
MAX6689
7-Channel Precision Temperature Monitor
ELECTRICAL CHARACTERISTICS (continued)
(VCC= +3.0V to +5.5V, VSTBY= VCC, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VCC= +3.3V and TA=
+25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
SMBus INTERFACE (SCL, SDA), STBY
Logic-Input Low VoltageVIL0.8V
VCC = 3.0V2.2Logic-Input High VoltageVIHVCC = 5.0V2.4V
Input Leakage Current-1+1µA
Output Low VoltageVOLISINK = 6mA0.3V
Input CapacitanceCIN5pF
SMBus-COMPATIBLE TIMING (Figures 3 and 4) (Note 2)
Serial-Clock FrequencyfSCL(Note 3)400kHz
fSCL = 100kHz4.7Bus Free Time Between STOP
and START ConditiontBUFfSCL = 400kHz1.6µs
fSCL = 100kHz4.7START Condition Setup TimefSCL = 400kHz0.6µs
90% of SCL to 90% of SDA,
fSCL = 100kHz0.6
Repeat START Condition Setup
TimetSU:STA
90% of SCL to 90% of SDA,
fSCL = 400kHz0.6
START Condition Hold TimetHD:STA10% of SDA to 90% of SCL0.6µs
90% of SCL to 90% of SDA,
fSCL = 100kHz4
STOP Condition Setup TimetSU:STO
90% of SCL to 90% of SDA,
fSCL = 400kHz0.6
10% to 10%, fSCL = 100kHz1.3Clock-Low PeriodtLOW10% to 10%, fSCL = 400kHz1.3µs
Clock-High PeriodtHIGH90% to 90%0.6µs
fSCL = 100kHz300Data Hold TimetHD:DATfSCL = 400kHz (Note 4)900ns
fSCL = 100kHz250Data Setup TimetSU:DATfSCL = 400kHz100ns
fSCL = 100kHz1Receive SCL/SDA Rise TimetRfSCL = 400kHz0.3µs
Receive SCL/SDA Fall TimetF300ns
Pulse Width of Spike SuppressedtSP050ns
SMBus TimeouttTIMEOUTSDA low period for interface reset253745ms
Note 1:All parameters are tested at TA= +85°C. Specifications over temperature are guaranteed by design.
Note 2:Timing specifications are guaranteed by design.
Note 3:The serial interface resets when SCL is low for more than tTIMEOUT.
Note 4:A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SCL’s falling edge.
MAX6689
7-Channel Precision Temperature Monitor
Typical Operating Characteristics
(VCC= 3.3V, VSTBY= VCC, TA= +25°C, unless otherwise noted.)
SOFTWARE STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6689 toc01
SUPPLY VOLTAGE (V)
STANDBY SUPPLY CURRENT (
SUPPLY CURRENT
vs. SUPPLY VOLTAGEMAX6689 toc02
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
MAX6689 toc03
REMOTE-DIODE TEMPERATURE (°C)
TEMPERATURE ERROR (255075100125
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATUREMAX6689 toc04
DIE TEMPERATURE (°C)
TEMPERATURE ERROR (
REMOTE-DIODE TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCYMAX6689 toc05
FREQUENCY (MHz)
TEMPERATURE ERROR (
100mVP-P
LOCAL TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCYMAX6689 toc06
FREQUENCY (MHz)
TEMPERATURE ERROR (
100mVP-P
REMOTE TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCYMAX6689 toc07
FREQUENCY (MHz)
TEMPERATURE ERROR (0.10.01
100mVP-P
MAX6689
7-Channel Precision Temperature Monitor
REMOTE TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCYMAX6689 toc08
FREQUENCY (MHz)
TEMPERATURE ERROR (0.10.01
100mVP-P
Typical Operating Characteristics (continued)(VCC= 3.3V, VSTBY= VCC, TA= +25°C, unless otherwise noted.)
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCEMAX6689 toc09
DXP-DXN CAPACITANCE (nF)
TEMPERATURE ERROR (
°C)
Pin Description
PINNAMEFUNCTIONDXP1
Combined Current Source and A/D Positive Input for Channel 1 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no
remote diode is used. Place a 2200pF capacitor between DXP1 and DXN1 for noise filtering.DXN1Cathode Input for Channel 1 Remote Diode. Connect the cathode of the channel 1 remote-diode-
connected transistor to DXN1.DXP2
Combined Current Source and A/D Positive Input for Channel 2 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no
remote diode is used. Place a 2200pF capacitor between DXP2 and DXN2 for noise filtering.DXN2Cathode Input for Channel 2 Remote Diode. Connect the cathode of the channel 2 remote-diode-
connected transistor to DXN2.DXP3
Combined Current Source and A/D Positive Input for Channel 3 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no
remote diode is used. Place a 2200pF capacitor between DXP3 and DXN3 for noise filtering.DXN3Cathode Input for Channel 3 Remote Diode. Connect the cathode of the channel 1 remote-diode-
connected transistor to DXN3.DXP4
Combined Current Source and A/D Positive Input for Channel 4 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no
remote diode is used. Place a 2200pF capacitor between DXP4 and DXN4 for noise filtering.DXN4Cathode Input for Channel 4 Remote Diode. Connect the cathode of the channel 1 remote-diode-
connected transistor to DXN4.
MAX6689
Detailed DescriptionThe MAX6689 is a precision multichannel temperature
monitor that features one local and six remote tempera-
ture-sensing channels with a programmable alert
threshold for each temperature channel and a program-
mable overtemperature threshold for channels 1, 4, 5,
and 6 (see Figure 1). Communication with the MAX6689
is achieved through the SMBus serial interface and a
dedicated alert pin. The alarm outputs, OVERTand
ALERT, assert if the software-programmed temperature
thresholds are exceeded. ALERTtypically serves as an
interrupt, while OVERTcan be connected to a fan, sys-
tem shutdown, or other thermal-management circuitry.
ADC Conversion SequenceIn the default conversion mode, the MAX6689 starts the
conversion sequence by measuring the temperature on
channel 1, followed by 2, 3, local channel, 4, 5, and 6.
The conversion result for each active channel is stored
in the corresponding temperature data register.
In some systems, one of the remote thermal diodes may
be monitoring a location that experiences temperature
changes that occur much more rapidly than in the other
channels. If faster temperature changes must be moni-
allows channel 1 to be monitored at a faster rate than
the other channels. In this mode (set by writing a 1 to bit
4 of the configuration 1 register), measurements of
channel 1 alternate with measurements of the other
channels. The sequence becomes channel 1, channel
2, channel 1, channel 3, channel 1, etc. Note that the
time required to measure all seven channels is consid-
erably greater in this mode than in the default mode.
Low-Power Standby ModeEnter software standby mode by setting the STOP bit to
1 in the configuration 1 register. Enter hardware standby
by pulling STBYlow.Software standby mode disables
the ADC and reduces the supply current to approxi-
mately 30µA.Hardware standby mode halts the ADC
clock, but the supply current is approximately 350µA.
During either software or hardware standby, data is
retained in memory. During hardware standby, the
SMBus interface is inactive. During software standby, the
SMBus interface is active and listening for commands.
The timeout is enabled if a start condition is recognized
on SMBus. Activity on the SMBus causes the supply cur-
rent to increase. If a standby command is received while
a conversion is in progress, the conversion cycle is inter-
7-Channel Precision Temperature Monitor
PINNAMEFUNCTIONDXP5
Combined Current Source and A/D Positive Input for Channel 5 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no
remote diode is used. Place a 2200pF capacitor between DXP5 and DXN5 for noise filtering.DXN5Cathode Input for Channel 5 Remote Diode. Connect the cathode of the channel 1 remote-diode-
connected transistor to DXN5.DXN6Cathode Input for Channel 6 Remote Diode. Connect the cathode of the channel 1 remote-diode-
connected transistor to DXN6.DXP6
Combined Current Source and A/D Positive Input for Channel 6 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no
remote diode is used. Place a 2200pF capacitor between DXP6 and DXN6 for noise filtering.STBYActive-Low Standby Input. Drive STBY logic-low to place the MAX6689 in standby mode, or logic-high
for operate mode. Temperature and threshold data are retained in standby mode.N.C.No Connection. Must be connected to ground.OVERTOvertemperature Active-Low, Open-Drain Output. OVERT asserts low when the temperature of
channels 1, 4, 5, and 6 exceeds the programmed threshold limit.VCCSupply Voltage Input. Bypass to GND with a 0.1µF capacitor.ALERTSMBus Alert (Interrupt), Active-Low, Open-Drain Output. ALERT asserts low when the temperature of
any channel exceeds the programmed ALERT threshold.SMBDATASMBus Serial-Data Input/Output. Connect to a pullup resistor.SMBCLKSMBus Serial-Clock Input. Connect to a pullup resistor.GNDGround
Pin Description (continued)
rupted, and the temperature registers are not updated.
The previous data is not changed and remains available.
SMBus Digital InterfaceFrom a software perspective, the MAX6689 appears as
a series of 8-bit registers that contain temperature mea-
surement data, alarm threshold values, and control bits.
A standard SMBus-compatible, 2-wire serial interface is
used to read temperature data and write control bits
and alarm threshold data. The same SMBus slave
address also provides access to all functions.
The MAX6689 employs four standard SMBus protocols:
write byte, read byte, send byte, and receive byte
(Figure 2). The shorter receive byte protocol allows
quicker transfers, provided that the correct data regis-
ter was previously selected by a read byte instruction.
Use caution with the shorter protocols in multimaster
systems, since a second master could overwrite the
command byte without informing the first master. Figure
3 is the SMBus write-timing diagram and Figure 4 is the
SMBus read-timing diagram.
The remote diode 1 measurement channel provides 11
bits of data (1 LSB = 0.125°C). All other temperature-
measurement channels provide 8 bits of temperature
data (1 LSB = 1°C). The 8 most significant bits (MSBs)
can be read from the local temperature and remote
temperature registers. The remaining 3 bits for remote
diode 1 can be read from the extended temperature
MAX6689
7-Channel Precision Temperature MonitorFigure 1. Internal Block Diagram
DXP1
DXN1
DXP2
DXN2
DXP3
DXN3
DXP4
DXN4
DXP5
DXN5
DXP6
DXN6
INPUT
BUFFER
10/100μA
VCC
REF
COUNT
COUNTER
COMMAND BYTE
REMOTE TEMPERATURES
LOCAL TEMPERATURES
REGISTER BANK
ALERT THRESHOLD
OVERT THRESHOLD
ALERT RESPONSE ADDRESS
ALARM
ALU
ADC
SMBus
INTERFACE
MAX6689
SCLSDA
OVERT
AVERT
STBY
MAX6689register. If extended resolution is desired, the extended
resolution register should be read first. This prevents
the most significant bits from being overwritten by new
conversion results until they have been read. If the
most significant bits have not been read within an
SMBus timeout period (nominally 37ms), normal updat-
ing continues. Table 1 shows the main temperature
register (high-byte) data format, and Table 2 shows the
extended resolution register (low-byte) data format.
Diode Fault DetectionIf a channel’s input DXP_ and DXN_ are left open, the
MAX6689 detects a diode fault. An open diode fault does
not cause either ALERTor OVERTto assert. A bit in the
status register for the corresponding channel is set to 1
and the temperature data for the channel is stored as all
1s (FFh). It takes approximately 4ms for the MAX6689 to
detect a diode fault. Once a diode fault is detected, the
MAX6689 goes to the next channel in the conversion
sequence. Depending on operating conditions, a shorted
diode may or may not cause ALERTor OVERTto assert,
so if a channel will not be used, disconnect its DXP and
7-Channel Precision Temperature MonitorFigure 2. SMBus Protocols
TEMP (°C)DIGITAL OUTPUT> +1270111 1111
+1270111 1111
+1260111 1110
+250001 10010000 0000
< 00000 0000
Diode fault (open)1111 1111
Diode fault (short)1111 1111 or 1110 1110
Table 1. Main Temperature Register
(High-Byte) Data Format
TEMP (°C)DIGITAL OUTPUT000X XXXX
+0.125001X XXXX
+0.250010X XXXX
+0.375011X XXXX
+0.500100X XXXX
+0.625101X XXXX
+0.725110X XXXX
Table 2. Extended Resolution Temperature
Register (Low-Byte) Data FormatADDRESSWRACKACKPDATAACKCOMMAND7 BITS18 BITS8 BITS
SLAVE ADDRESS: EQUIVA-
LENT TO CHIP-SELECT LINE OF
A 3-WIRE INTERFACE
DATA BYTE: DATA GOES INTO THE REGISTER
SET BY THE COMMAND BYTE (TO SET
THRESHOLDS, CONFIGURATION MASKS, AND
SAMPLING RATE)
WRITE BYTE FORMATADDRESSADDRESSWRACKACKPSRDACK///DATACOMMAND7 BITS7 BITS8 BITS8 BITS
READ BYTE FORMATSLAVE ADDRESS: EQUIVA-
LENT TO CHIP SELECT LINE
COMMAND BYTE: SELECTS
WHICH REGISTER YOU ARE
REDING FROM
ADDRESSWRACKACKCOMMAND7 BITS8 BITS
SEND BYTE FORMATCOMMAND BYTE: SENDS COM-
MAND WITH NO DATA, USUALLY
USED FOR ONE-SHOT COMMAND
ADDRESSRDACK///DATA7 BITS8 BITS
RECEIVE BYTE FORMATDATA BYTE: READS DATA FROM
THE REGISTER COMMANDED
BY THE LAST READ BYTE OR
WRITE BYTE TRANSMISSION;
ALSO USED FOR SMBUS ALERT
RESPONSE RETURN ADDRESS
SLAVE ADDRESS: REPEATED
DUE TO CHANGE IN DATA-
FLOW DIRECTION
DATA BYTE: READS FROM
THE REGISTER SET BY THE
COMMAND BYTE
S = START CONDITION.
P = STOP CONDITION.
SHADED = SLAVE TRANSMISSION.
/// = NOT ACKNOWLEDGED.
Alarm Threshold RegistersThere are 11 alarm threshold registers that store over-
temperature ALERTand OVERTthreshold values.
Seven of these registers are dedicated to store one
local alert temperature threshold limit and six remote
alert temperature threshold limits (see the ALERT
Interrupt Modesection). The remaining four registers
are dedicated to remote channels 1, 4, 5, and 6 to store
overtemperature threshold limits (see theOVERT
Overtemperature Alarmssection). Access to these reg-
isters is provided through the SMBusinterface.
ALERTInterrupt ModeAn ALERTinterrupt occurs when the internal or external
temperature reading exceeds a high-temperature limit
(user programmable). The ALERTinterrupt output sig-
nal can be cleared by reading the status register(s)
associated with the fault(s) or by successfully respond-
ing to an alert response address transmission by the
master. In both cases, the alert is cleared but is
reasserted at the end of the next conversion if the fault
condition still exists. The interrupt does not halt automat-
ic conversions. The ALERToutput is open drain so that
multiple devices can share a common interrupt line. All
ALERTinterrupts can be masked using the configuration
3 register. The POR state of these registers is shown in
Table 1.
MAX6689
7-Channel Precision Temperature MonitorSMBCLK
A = START CONDITION.
B = MSB OF ADDRESS CLOCKED INTO SLAVE.
C = LSB OF ADDRESS CLOCKED INTO SLAVE.
D = R/W BIT CLOCKED INTO SLAVE.CDEFGHIJ
SMBDATA
tSU:STAtHD:STA
tLOWtHIGH
tSU:DATtSU:STOtBUFK
E = SLAVE PULLS SMBDATA LINE LOW.
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER.
G = MSB OF DATA CLOCKED INTO SLAVE.
H = LSB OF DATA CLOCKED INTO SLAVE.
I = MASTER PULLS DATA LINE LOW.
J = ACKNOWLEDGE CLOCKED INTO SLAVE.
K = ACKNOWLEDGE CLOCK PULSE.
L = STOP CONDITION.
M = NEW START CONDITION.
Figure 3. SMBus Write-Timing Diagram
SMBCLKCDEFGHIJK
SMBDATA
tSU:STAtHD:STA
tLOWtHIGH
tSU:DATtHD:DATtSU:STOtBUF
A = START CONDITION.
B = MSB OF ADDRESS CLOCKED INTO SLAVE.
C = LSB OF ADDRESS CLOCKED INTO SLAVE.
D = R/W BIT CLOCKED INTO SLAVE.
E = SLAVE PULLS SMBDATA LINE LOW. M
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER.
G = MSB OF DATA CLOCKED INTO MASTER.
H = LSB OF DATA CLOCKED INTO MASTER.
I = MASTER PULLS DATA LINE LOW.
J = ACKNOWLEDGE CLOCKED INTO SLAVE.
K = ACKNOWLEDGE CLOCK PULSE.
L = STOP CONDITION.
M = NEW START CONDITION.
Figure 4. SMBus Read-Timing Diagram
MAX6689
ALERTResponse AddressThe SMBus alert response interrupt pointer provides
quick fault identification for simple slave devices that
lack the complex logic needed to be a bus master.
Upon receiving an interrupt signal, the host master can
broadcast a receive byte transmission to the alert
response slave address (see the Slave Addressessec-
tion). Then, any slave device that generated an inter-
rupt attempts to identify itself by putting its own
address on the bus.
The alert response can activate several different slave
devices simultaneously, similar to the I2C General Call.
If more than one slave attempts to respond, bus arbitra-
tion rules apply, and the device with the lower address
code wins. The losing device does not generate an
acknowledgment and continues to hold the ALERTline
low until cleared. (The conditions for clearing an alert
vary depending on the type of slave device.)
Successful completion of the alert response protocol
clears the output latch. If the condition that caused the
alert still exists, the MAX6689 reasserts the ALERT
interrupt at the end of the next conversion.
OVERTOvertemperature AlarmsThe MAX6689 has four overtemperature registers that
store remote alarm threshold data for the OVERToutput.
OVERTis asserted when a channel’s measured temper-
ature is greater than the value stored in the correspond-
ing threshold register. OVERTremains asserted until the
temperature drops below the programmed threshold
minus 4°C hysteresis. An overtemperature output can
be used to activate a cooling fan, send a warning, initi-
ate clock throttling, or trigger a system shutdown to pre-
vent component damage. See Table 3 for the POR state
of the overtemperature threshold registers.
Command Byte FunctionsThe 8-bit command byte register (Table 3) is the master
index that points to the various other registers within the
MAX6689. This register’s POR state is 0000 0000.
Configuration Byte FunctionsThere are three read-write configuration registers
(Tables 4, 5, and 6) that can be used to control the
MAX6689’s operation.
Configuration 1 RegisterThe configuration 1 register (Table 4) has several func-
tions. Bit 7 (MSB) is used to put the MAX6689 either in
software standby mode (STOP) or continuous conver-
sion mode. Bit 6 resets all registers to their power-on
reset conditions and then clears itself. Bit 5 disables
the SMBus timeout. Bit 4 enables more frequent con-
versions on channel 1, as described in the ADC
Conversion Sequencesection. Bit 3 enables resistance
cancellation on channel 1. See the Series Resistance
Cancellationsection for more details. The remaining
bits of the configuration 1 register are not used. The
POR state of this register is 0000 0000 (00h).
Configuration 2 RegisterThe configuration 2 register functions are described in
Table 5. Bits [6:0] are used to mask the ALERTinterrupt
output. Bit 6 masks the local alert interrupt and bits 5
through bit 0 mask the remote alert interrupts. The
power-up state of this register is 0000 0000 (00h).
Configuration 3 RegisterTable 6 describes the configuration 3 register. Bits 5, 4,
3, and 0 mask the OVERTinterrupt output for channels
6, 5, 4, and 1. The remaining bits, 7, 6, 2, and 1, are
reserved. The power-up state of this register is 0000
0000 (00h).
Status Register FunctionsStatus registers 1, 2, and 3 (Tables 7, 8, and 9) indicate
which (if any) temperature thresholds have been
exceeded and if there is an open-circuit or short-circuit
fault detected with the external sense junctions. Status
register 1 indicates if the measured temperature has
exceeded the threshold limit set in the ALERTregisters
for the local or remote-sensing diodes. Status register 2
indicates if the measured temperature has exceeded
the threshold limit set in the OVERTregisters. Status
register 3 indicates if there is a diode fault (open or
short) in any of the remote-sensing channels.
Bits in the alert status register clear by a successful
read, but set again after the next conversion unless the
fault is corrected, either by a drop in the measured tem-
perature or an increase in the threshold temperature.
The ALERTinterrupt output follows the status flag bit.
Once the ALERToutput is asserted, it can be
deasserted by either reading status register 1 or by
successfully responding to an alert response address.
7-Channel Precision Temperature Monitor
