Maxim MAX6659MEE ±1â°c, smbus-compatible remote/local temperature sensors with overtemperature alarm Datasheet

19-2034; Rev 2; 3/02
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
Features
♦ Dual Channel: Measures Remote and Local
Temperature
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 programmable conversion rate, which allows the control of supply 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 conversion 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.
♦ Programmable Conversion Rate
(0.0625Hz to 16Hz)
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 overtemperature alarm pin for greater system reliability.
♦ 11-Bit, 0.125°C Resolution
♦ High Accuracy ±1°C (max) from +60°C to +100°C
(Remote)
♦ No Calibration Required
♦ Programmable Under/Overtemperature Alarms
♦ SMBus/I2C™-Compatible Interface
♦ Two Alarm Outputs: ALERT and OVERT1
(MAX6657 and MAX6658)
♦ Three Alarm Outputs: ALERT, OVERT1,
and OVERT2 (MAX6659)
Ordering Information
TEMP.
RANGE
PART
MAX6657MSA -55°C to +125°C 8 SO
0°C to +125°C
MAX6658MSA -55°C to +125°C 8 SO
-55°C to +125°C
MAX6659MEE -55°C to +125°C 16 QSOP
-55°C to +125°C
Pin Configurations
Applications
Desktop Computers
Notebook Computers
Servers
Workstations
TOP VIEW
VCC 1
16 N.C.
N.C. 2
15 STBY
DXP 3
14 SMBCLK
DXN 4
Typical Operating Circuit appears at the end of the
data sheet.
SMBus is a trademark of Intel Corp.
PINMEASURED
PACKAGE TEMP. RANGE
MAX6659
13 N.C.
12 SMBDATA
ADD 5
OVERT1 6
11 N.C.
GND 7
10 OVERT2
GND 8
9 ALERT
VCC 1
8 SMBCLK
DXP 2
DXN 3
7 SMBDATA
MAX6657
MAX6658
OVERT1 4
6 ALERT
5 GND
SO
QSOP
I2C is a trademark of Philips Corp.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX6657/MAX6658/MAX6659
General Description
The MAX6657/MAX6658/MAX6659 are precise, twochannel digital temperature sensors. Each accurately
measures the temperature of its own die and one
remote PN junction, and reports the temperature in digital 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.
MAX6657/MAX6658/MAX6659
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
ABSOLUTE MAXIMUM RATINGS
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
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.
ELECTRICAL CHARACTERISTICS
(Circuit of Typical Operating Circuit, 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.)
PARAMETER
SYMBOL
CONDITIONS
MIN
Temperature Resolution,
Legacy Mode
1
Temperature Resolution,
Extended Mode
0.125
Remote Temperature Error
(MAX6657)
Local Temperature Error
(MAX6657)
Remote Temperature Error
(MAX6658/MAX6659)
Local Temperature Error
(MAX6658/MAX6659)
Supply Voltage Range
Undervoltage Lockout Threshold
Power-On Reset (POR) Threshold
2
Bits
11
Bits
°C
TRJ = 0°C to +100°C, VCC = +3.3V (Note 1)
-3.0
+3.0
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
+3.0
TA = 0°C to +125°C, VCC = +3.3V
-5.0
+5.0
TRJ = +60°C to +100°C, VCC = +3.3V
(Note 1)
-1.0
1.0
TRJ = 0°C to +100°C, VCC = +3.3V (Note 1)
-3.0
3.0
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
+3.0
TA = -55°C to +125°C, VCC = +3.3V (Note 2)
-5.0
Falling edge of VCC disables ADC
2.60
1.5
SMBus static
Operating Current
During conversion
°C
°C
2.80
0.6
m°C/V
V
2.95
2.0
V
mV
2.5
90
Standby Supply Current
°C
5.5
90
VCC, falling edge
°C
+5.0
0.2
3.0
POR Threshold Hysteresis
Average Operating Current
8
+1.0
Undervoltage Lockout Hysteresis
UNITS
°C
-1.0
VCC
UVLO
MAX
TRJ = +60°C to +100°C, VCC = +3.3V
(Note 1)
3.0V ≤ VCC ≤ 5.5V
Line Regulation
TYP
V
mV
3
10
µA
0.5
1.0
mA
0.25 conversions/s
40
70
2 conversions/s
150
250
_______________________________________________________________________________________
µA
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
(Circuit of Typical Operating Circuit, 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.)
PARAMETER
Conversion Time
SYMBOL
tCONV
CONDITIONS
From stop bit to conversion completed
(Note 4)
MIN
TYP
MAX
UNITS
95
125
156
ms
Conversion Timing Error
DXP and DXN Leakage Current
Remote-Diode Source Current
In standby mode
IRJ
±25
%
100
nA
High level
80
100
120
Low level
8
10
12
VOL = 0.4V
1
VOL = 0.6V
6
µA
(ALERT, OVERT)
Output Low Sink Current
Output High Leakage Current
mA
VOH = 5.5V
1
µA
0.8
V
SMBus-COMPATIBLE INTERFACE (SMBCLK, SMBDATA, STBY)
Logic Input Low Voltage
Logic Input High Voltage
Input Leakage Current
VIL
VIH
ILEAK
Output Low Sink Current
IOL
Input Capacitance
CIN
VCC = +3.0V
2.2
VCC = +5.5V
2.4
V
VIN = GND or VCC
VOL = 0.6V
±1
6
µA
mA
5
pF
SMBus-COMPATIBLE TIMING (Note 4)
Serial Clock Frequency
fSCL
Bus Free Time Between STOP
and START Condition
tBUF
(Note 5)
START Condition Setup Time
Repeat START Condition Setup
Time
100
kHz
4.7
µs
4.7
µs
tSU:STA
90% to 90%
50
ns
START Condition Hold Time
tHD:STA
10% of SMBDATA to 90% of SMBCLK
4
µs
STOP Condition Setup Time
tSU:STO
90% of SMBCLK to 90% of SMBDATA
4
µs
Clock Low Period
tLOW
10% to 10%
4.7
µs
Clock High Period
tHIGH
90% to 90%
4
µs
(Note 6)
0
µs
Data Setup Time
tHD:DAT
Receive SCL/SDA Rise Time
tR
1
Receive SCL/SDA Fall Time
tF
300
ns
50
ns
45
ms
Pulse Width of Spike Suppressed
SMBus Timeout
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
tSP
0
SMBDATA low period for interface reset
25
37
µs
TA = +25°C to +85°C.
If both the local and the remote junction are below TA = -20°C, then VCC > 3.15V.
For conversion rates of 4Hz or slower, the conversion time doubles.
Timing specifications guaranteed by design.
The serial interface resets when SMBCLK is low for more than tTIMEOUT.
A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SMBCLK's falling edge.
_______________________________________________________________________________________
3
MAX6657/MAX6658/MAX6659
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VCC = +3.3V, TA = +25°C, unless otherwise noted.)
3.5
3.0
MAX6657 toc03
2
TEMPERATURE ERROR (°C)
OPERATING SUPPLY CURRENT (µA)
8Hz AND 16Hz ARE 1°C RESOLUTION
4.0
3
MAX6657 toc02
600
MAX6657 toc01
4.5
STANDBY SUPPLY CURRENT (µA)
MAX6659
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
OPERATING SUPPLY CURRENT
vs. CONVERSION RATE
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
400
200
1
0
-1
-2
FAIRCHILD 2N3906
0
4.0
4.5
5.0
0.063 0.125 0.25 0.5
5.5
1
2
4
8
16
SUPPLY VOLTAGE (V)
CONVERSION RATE (Hz)
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
TEMPERATURE ERROR vs.
POWER-SUPPLY NOISE FREQUENCY
TEMPERATURE ERROR (°C)
2
1
0
-1
-1
VIN = SQUARE WAVE APPLIED TO VCC
WITH NO 0.1µF VCC CAPACITOR
-3
-55
-30
-5
20
45
70
95
10k
120
100k
1M
10M
-2
VIN = 10mVP-P SQUARE WAVE
APPLIED TO DXP-DXN
-2
-3
0.01k
1k
100k
MAX6657 toc08
-1
-2
-3
-4
-5
-3
10k
100k
1M
FREQUENCY (Hz)
4
100M
0
MAX6657 toc07
-1
10M
100M
95
120
VIN = AC-COUPLED TO DXN
VIN = 100mVp-p
TEMPERATURE ERROR vs.
DXP-DXN CAPACITANCE
TEMPERATURE ERROR (°C)
TEMPERATURE ERROR (°C)
0
70
-1
FREQUENCY (Hz)
TEMPERATURE ERROR vs.
DIFFERENTIAL-MODE NOISE FREQUENCY
1
45
0
FREQUENCY (Hz)
TEMPERATURE (°C)
20
1
-2
-3
-5
TEMPERATURE ERROR vs.
COMMON-MODE NOISE FREQUENCY
0
-2
-30
TEMPERATURE (°C)
1
MAX6657 toc04
3
-55
MAX6657 toc06
3.5
MAX6657 toc05
3.0
-3
TEMPERATURE ERROR (°C)
2.5
TEMPERATURE ERROR (°C)
MAX6657/MAX6658/MAX6659
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
0
10 20 30 40 50 60 70 80 90 100
DXP-DXN CAPACITANCE (nF)
_______________________________________________________________________________________
10M
1G
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
PIN
NAME
FUNCTION
MAX6657
MAX6658
MAX6659
1
1
VCC
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.
2
3
DXP
Combined Remote-Diode 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.
3
4
DXN
Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally
biased to one diode drop above ground.
4
6
OVERT1
Overtemperature Active-Low Output, Open-Drain. Output is logic low only when
temperature is above the software programmed threshold.
5
7, 8
GND
Ground
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.
6
9
ALERT
7
12
SMBDATA
8
14
SMBCLK
—
5
ADD
—
10
OVERT2
—
15
STBY
Hardware 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, 16
N.C.
Not internally connected. Do not make connections to these pins.
SMBus Serial-Data Input/Output, Open-Drain
SMBus Serial-Clock Input
SMBus Address-Select Pin. The MAX6659 is set to one of three available addresses
(connect to VCC, GND, or leave open). See Slave Addresses section.
Overtemperature Active-Low Output, Open-Drain. Output is logic low only when
temperature is above the software programmed threshold.
_______________________________________________________________________________________
5
MAX6657/MAX6658/MAX6659
Pin Description
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
MAX6657/MAX6658/MAX6659
Functional Diagram
VCC
MAX6657
MAX6658
MAX6659
2
DXP
MUX
REMOTE
DXN
(STBY)
CONTROL
LOGIC
ADC
LOCAL
DIODE
FAULT
ALERT
Q
S
R
REGISTER BANK
COMMAND BYTE
REMOTE TEMPERATURE
LOCAL TEMPERATURE
ALERT THRESHOLD
OVERT1
S
Q
R
ALERT RESPONSE
ADDRESS
(OVERT2)
S
OVERT1 THRESHOLD
R
(OVERT2 THRESHOLD)
Q
MAX6659 ONLY
Detailed Description
The MAX6657/MAX6658/MAX6659 are temperature
sensors designed to work in conjunction with a microprocessor or other intelligence in thermostatic,
process-control, or monitoring applications. Communication with the MAX6657/MAX6658/MAX6659
occurs through the SMBus serial interface and dedicated alert pins. Two independent overtemperature alarms
(OVERT1 and OVERT2) are asserted if their software
programmed temperature thresholds are exceeded.
OVERT1 and OVERT2 can be connected to fans, a system shutdown, or other thermal management circuitry.
The MAX6657/MAX6658/MAX6659 convert temperatures to digital data either at a programmed rate or a
single conversion. Conversions have a 0.125°C resolution (extended resolution) or 1°C resolution (legacy resolution). Extended resolution represents temperature as
6
8
SMBus
READ
8
WRITE
SMBDATA
SMBCLK
7
(ADD)
ADDRESS
DECODER
( ) ARE FOR MAX6659 ONLY
10 bits + sign bit and is available for autonomous conversions that are 4Hz and slower and single-shot conversions. Legacy resolution represents temperature as
7 bits + sign bit and allows for faster autonomous conversion rates of 8Hz and 16Hz.
ADC and Multiplexer
The 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 voltage and compute the temperature based on this voltage. If the remote channel is not used, connect DXP to
DXN. Do not leave DXP and DXN unconnected. When a
conversion is initiated, both channels are converted
_______________________________________________________________________________________
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
MANUFACTURER
Central Semiconductor (USA)
Fairchild Semiconductor (USA)
On Semiconductor (USA)
Rohm Semiconductor (USA)
Samsung (Korea)
Siemens (Germany)
Zetex (England)
MODEL NUMBER
CMPT3904
2N3904, 2N3906
2N3904, 2N3906
SST3904
KST3904-TF
SMBT3904
FMMT3904CT-ND
Note: Transistors must be diode connected (base shorted to
collector).
whether they are used or not. The DXN input is biased
at one VBE above 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 Sequence
A conversion sequence consists of a local temperature
measurement and a remote temperature measurement.
Each time a conversion begins, whether initiated automatically 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 conversion. 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 Selection
The MAX6657/MAX6658/MAX6659 can directly measure the die temperature of CPUs and other ICs that
have on-board temperature-sensing diodes (see
Typical Operating Circuit) or they can measure the temperature 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 collector PNP transistor. For best accuracy, the discrete transistor should be a small-signal device with its collector
and base connected together. Accuracy has been
experimentally verified for all the devices listed in Table 1.
The transistor must be a small-signal type with a relatively 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 temperature, 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 specifications for forward current gain (50 < β < 150, for
example) indicate that the manufacturer has good
process controls and that the devices have consistent
VBE characteristics.
Thermal Mass and Self-Heating
When 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 measurements 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 virtually no effect; the measured temperature of the junction
tracks the actual temperature within a conversion cycle.
When measuring temperature with discrete remote sensors, smaller packages (i.e., a SOT23) yield the best
thermal response times. Take care to account for thermal gradients between the heat source and the sensor,
and ensure that stray air currents across the sensor
package do not interfere with measurement accuracy.
Self-heating does not significantly affect measurement
accuracy. Remote-sensor self-heating due to the diode
current source is negligible. For the local diode, the
worst-case error occurs when autoconverting at the
fastest rate and simultaneously sinking maximum current at the ALERT output. For example, with V CC =
+5.0V, a 16Hz conversion rate and ALERT sinking
1mA, the typical power dissipation is:
VCC x 450µA + 0.4V x 1mA = 2.65mW
θJ-A for the 8-pin SO package is about +170°C/W, so
assuming no copper PC board heat sinking, the resulting temperature rise is:
∆T = 2.65mW x +170°C/W = +0.45°C
Even under these engineered circumstances, it is difficult to introduce significant self-heating errors.
ADC Noise Filtering
The integrating ADC used has good noise rejection for
low-frequency signals such as 60Hz/120Hz power-supply hum. In noisy environments, high-frequency noise
reduction is needed for high-accuracy remote mea-
_______________________________________________________________________________________
7
MAX6657/MAX6658/MAX6659
Table 1. Remote-Sensor Transistor
MAX6657/MAX6658/MAX6659
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
surements. 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.
GND
10MILS
10MILS
DXP
MINIMUM
10MILS
DXN
10MILS
GND
Figure 1. Recommended DXP-DXN PC Traces
PC Board Layout
Follow these guidelines to reduce the measurement
error of the temperature sensors:
1) Place the MAX6657/MAX6658/MAX6659 as close
as is practical to the remote diode. In noisy environments, such as a computer motherboard, this distance 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.
2) Do not route the DXP-DXN lines next to the deflection coils of a CRT. Also, do not route the traces
across fast digital signals, which can easily introduce +30°C error, even with good filtering.
3) 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 20MΩ leakage 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).
4) Route through as few vias and crossunders as possible to minimize copper/solder thermocouple
effects.
8
5) 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 negligible error.
6) 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.
7) Add a 200Ω resistor in series with V CC for best
noise filtering (see Typical Operating Circuit).
Twisted-Pair and Shielded Cables
Use 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 microphones. For example, Belden #8451 works well for distances 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 capacitance 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 1Ω of series resistance, the error is approximately +1/2°C.
Low-Power Standby Mode
Standby mode reduces the supply current to less than
10µA by disabling the ADC. Enter hardware standby
(MAX6659 only) by forcing the STBY pin 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 memory, and the SMB interface is alive and listening for
SMBus commands. The only difference is that in software standby mode, the one-shot command initiates a
conversion. With hardware standby, the one-shot command is ignored. Activity on the SMBus causes the
device to draw extra supply current.
Driving the STBY pin low overrides any software conversion command. If a hardware or software standby
command is received while a conversion is in progress,
the conversion cycle is interrupted, and the tempera-
_______________________________________________________________________________________
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
SMBus Digital Interface
From a software perspective, each of the MAX6657/
MAX6658/MAX6659 appears as a series of 8-bit registers that contain temperature 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
device responds to the same SMBus slave address for
access to all functions.
The MAX6657/MAX6658/MAX6659 employ four standard SMBus protocols: Write Byte, Read Byte, Send
Byte, and Receive Byte (Figures 2, 3, and 4). 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 multimaster systems, since a
second master could overwrite the command byte without informing the first master.
When the conversion rate is greater than 4Hz, temperature
data can be read from the Read Internal Temperature
(00h) and Read External Temperature (01h) registers.
Write Byte Format
S
ADDRESS
WR
ACK
COMMAND
7 bits
ACK
DATA
8 bits
Slave Address: equivalent to chip-select line of
a 3-wire interface
ACK
P
8 bits
Command Byte: selects which
register you are writing to
1
Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
Read Byte Format
ADDRESS
WR
ACK
7 bits
COMMAND
ACK
RD
ACK
7 bits
Command Byte: selects
which register you are
reading from
Send Byte Format
DATA
///
P
8 bits
Slave Address: repeated
due to change in dataflow direction
Data Byte: reads from
the register set by the
command byte
Receive Byte Format
WR
7 bits
ACK
COMMAND
ACK
P
8 bits
Command Byte: sends command with no data, usually
used for one-shot command
S = Start condition
P = Stop condition
ADDRESS
8 bits
Slave Address: equivalent to chip-select line
ADDRESS
S
Shaded = Slave transmission
/// = Not acknowledged
S
ADDRESS
7 bits
RD
ACK
DATA
///
P
8 bits
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
Figure 2. SMBus Protocols
______________________________________________________________________________________
9
MAX6657/MAX6658/MAX6659
The temperature data format is 7 bits + sign in two'scomplement form for each channel, with the LSB representing 1°C (Table 2). The MSB is transmitted first.
When the conversion rate is 4Hz or less, the first 8 bits
of temperature data can be read from the Read Internal
Temperature (00h) and Read External Temperature
(01h) registers, the same as for faster conversion rates.
An additional 3 bits can be read from the Read External
Extended Temperature (10h) and Read Internal
Extended Temperature (11h) registers, which extends
the data to 10 bits + sign and the resolution to
+0.125°C per LSB (Table 3).
When a conversion is complete, the Main register and
the Extended register are updated almost simultaneously. Ensure that no conversions are completed
between reading the Main and Extended registers so
that when data that is read, both registers contain the
result of the same conversion.
To ensure valid extended data, read extended resolution temperature data using one of the following
approaches:
1) Put the MAX6657/MAX6658/MAX6659 into standby
mode by setting bit 6 of the Configuration register to
ture registers are not updated. The previous data is not
changed and remains available.
MAX6657/MAX6658/MAX6659
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
A
tLOW
B
tHIGH
C
D
E
F
G
H
I
J
K
L
M
SMBCLK
SMBDATA
tHD:STA
tSU:STA
tSU:DAT
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
tHD:DAT
tSU:STO tBUF
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
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
Figure 3. SMBus Write Timing Diagram
A
tLOW
B
tHIGH
C
D
E
F
G
H
I
J
K
L
M
SMBCLK
SMBDATA
tSU:STA
tHD:STA
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
tSU:DAT
tHD:DAT
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
tSU:STO tBUF
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
Figure 4. SMBus Read Timing Diagram
1. Initiate a one-shot conversion using Command
Byte 0Fh. When this conversion is complete, read
the contents of the Temperature Data registers.
2) If the MAX6657/MAX6658/MAX6659 are in run mode,
read the Status register. If a conversion is in
progress, the BUSY bit is set to 1. Wait for the conversion to complete as indicated by the BUSY bit
being set to 0, then read the Temperature Data registers. Note that the power-on reset sets the conversion rate to 16Hz, so no extended data is valid
without reducing the conversion rate to 4Hz or less.
10
Diode Fault Alarm
There is a continuity fault detector at DXP that detects
an open circuit between DXP and DXN, or a DXP short
to VCC, GND, or DXN. If an open or short circuit exists,
the external temperature register is loaded with 1000
0000. Additionally, if the fault is an open circuit, bit 2
(OPEN) of the status byte is set to 1 and the ALERT condition is activated at the end of the conversion.
Immediately after POR, the Status register indicates that
no fault is present until the end of the first conversion.
______________________________________________________________________________________
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
DIGITAL OUTPUT
TEMP (°C)
MAX6657
MAX6658
MAX6659
Table 3. Extended Resolution Register
FRACTIONAL
TEMPERATURE
CONTENTS OF
EXTENDED REGISTER
0.000
000X XXXX
001X XXXX
130.00
0 111 1111
0 111 1111
0.125
127.00
0 111 1111
0 111 1111
0.250
010X XXXX
126.00
0 111 1111
0 111 1111
0.375
011X XXXX
0 001 1001
0.500
100X XXXX
25
0 001 1001
0.00
0 000 0000
0 000 0000
0.625
101X XXXX
-1
1 000 0000
1 111 1111
0.750
110X XXXX
0.875
111X XXXX
-25
1 000 0000
1 110 0111
-55
1 000 0000
1 100 1001
Diode Fault
(Short or Open)
1 000 0000
1 000 0000
Note: Extended resolution applies only for conversion rates of
4Hz and slower.
Alert Response Address
Alarm Threshold Registers
Four registers store ALERT threshold values—one hightemperature (THIGH) and one low-temperature (TLOW)
register each for the local and remote channels. If
either measured temperature equals or exceeds the
corresponding ALERT threshold value, the ALERT output is asserted.
The POR state of both ALERT THIGH registers is 0100
0110 or +70°C and the POR state of TLOW registers is
1100 1001 or -55°C.
Four additional registers store remote and local alarm
threshold data corresponding to the OVERT1 and
OVERT2 (MAX6659 only) outputs. The values stored in
these registers are high-temperature thresholds. If any
one of the measured temperatures equals or exceeds
the corresponding alarm threshold value, an OVERT
output is asserted. The POR state of the OVERT threshold is 0101 0101 or +85°C.
Alert Interrupts
An ALERT interrupt occurs when the internal or external
temperature reading exceeds a high or low temperature limit (user programmed) or when the remote diode
is disconnected (for continuity fault detection). The
ALERT interrupt output signal is latched and can be
cleared only by either reading the Status register or by
successfully responding to an Alert Response address.
In both cases, the alert is cleared even if the fault condition still exists, but is reasserted at the end of the next
conversion. The interrupt does not halt automatic conversions. The interrupt output pin is open-drain so that
multiple devices can share a common interrupt line.
The interrupt rate never exceeds the conversion rate.
The SMBus Alert Response interrupt pointer provides
quick fault identification for simple slave devices that
lack the complex, expensive logic needed to be a bus
master. Upon receiving an ALERT interrupt signal, the
host master can broadcast a Receive Byte transmission
to the Alert Response slave address (0001100). Then,
any slave device that generated an interrupt attempts
to identify itself by putting its own address on the bus
(Table 8).
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 arbitration rules apply, and the device with the lower address
code wins. The losing device does not generate an
acknowledge and continues to hold the ALERT line 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
interrupt latch, provided the condition that caused the
alert no longer exists. If the condition still exists, the
device reasserts the ALERT interrupt at the end of the
next conversion.
OVERT Overtemperature
Alarm/Warning Outputs
OVERT1 and OVERT2 (MAX6659 only) are asserted
when the temperature rises to a value programmed in
the appropriate threshold register. They are deasserted
when the temperature drops below this threshold minus
the hysteresis. An OVERT output can be used to activate a cooling fan, send a warning, or trigger a system
shutdown to prevent component damage. The HYST
byte sets the amount of hysteresis for both OVERT outputs. The data format for the HYST byte is the same for
the other temperature registers (Table 2).
______________________________________________________________________________________
11
MAX6657/MAX6658/MAX6659
Table 2. Data Format (Two's Complement)
MAX6657/MAX6658/MAX6659
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
Table 4. Command Byte Register Assignments
REGISTER
ADDRESS
POR STATE
RLTS
00h
0000 0000
Read Internal Temperature
FUNCTION
RRTE
01h
0000 0000
Read External Temperature
RSL
02h
1000 0000
Read Status Register
RCL
03h
0010 0000
Read Configuration Byte
RCRA
04h
0000 1000
Read Conversion Rate Byte
RLHN
05h
0100 0110
Read Internal High Limit
RLLI
06h
1100 1001
Read Internal Low Limit
RRHI
07h
0100 0110
Read External High Limit
RRLS
08h
1100 1001
Read External Low Limit
WCA
09h
0010 0000
Write Configuration Byte
WCRW
0Ah
0000 1000
Write Conversion Rate Byte
WLHO
0Bh
0100 0110
Write Internal High Limit
Write Internal Low Limit
WLLM
0Ch
1100 1001
WRHA
0Dh
0100 0110
Write External High Limit
WRLN
0Eh
1100 1001
Write External Low Limit
OSHT
0Fh
N/A
REET
10h
0000 0000
Read External Extended Temperature
RIET
11h
0000 0000
Read Internal Extended Temperature
One Shot
RWO2E
16h
0101 0101
Read/Write External OVERT2 Limit (MAX6659 only)
RW02I
17h
0101 0101
Read/Write Internal OVERT2 Limit (MAX6659 only)
RWOE
19h
0101 0101
Read/Write External OVERT1 Limit
RWOI
20h
0101 0101
Read/Write Internal OVERT1 Limit
HYST
21h
0000 1010
Overtemperature Hysteresis
—
FEh
4Dh
Read Manufacture ID
For example, OVERT1 has a threshold set to +50°C
and is connected to a fan. OVERT2 has a threshold of
+75°C and is connected to a system shutdown. If the
system reaches +50°C, the fan turns on, trying to cool
the system. If the system continues to heat up to the
critical temperature of +75°C, OVERT2 causes the system to shut down.
Command Byte Functions
The 8-bit Command Byte register (Table 4) is the master
index that points to the various other registers within the
MAX6657/MAX6658/MAX6659. This register’s POR state
is 0000 0000, so a Receive Byte transmission (a protocol
that lacks the command byte) occurring immediately
after POR returns the current local temperature data.
One-Shot
The one-shot command immediately forces a new conversion cycle to begin. If the one-shot command is
received when the MAX6657/MAX6658/MAX6659 are in
12
software standby mode (RUN/STOP bit = 1), a new
conversion is begun, after which the device returns to
standby mode. If a conversion is in progress when a
one-shot command is received, the command is
ignored. If a one-shot command is received in autoconvert mode (RUN/STOP bit = 0) between conversions, a
new conversion begins, the conversion rate timer is
reset, and the next automatic conversion takes place
after a full delay elapses.
Configuration Byte Functions
The Configuration Byte register (Table 5) is a Read-Write
register with several functions. Bit 7 is used to mask (disable) interrupts. Bit 6 puts the device into software standby mode (STOP) or autonomous (RUN) mode. Bit 5
selects the type of external junction (set to 1 for a substrate PNP on an IC or set to 0 for a discrete diode-connected transistor) for optimized measurements. Bits 0 to
4 are reserved and return a zero when read.
______________________________________________________________________________________
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
Table 5. Configuration-Byte Bit
Assignments
BIT
NAME
POR
STATE
7
(MSB)
MASK1
0
Masks ALERT interrupts if a 1.
6
RUN/STOP
0
Standby mode control bit; if a
1, standby mode is initiated.
1
Set to 1 when the remote
sensor is a substrate or
common collector PNP. Set to 0
when the remote sensor is a
diode-connected discrete
transistor.
5
SPNP
4 to 0
RFU
0
FUNCTION
Reserved
ALERT output follows the status flag bit. Both are
cleared when successfully read, but if the condition still
exists, they reassert at the end of the next conversion.
The bits indicating OVERT1 (bits 0 and 1) are cleared
only when the condition no longer exists. Reading the
status byte does not clear the OVERT1 outputs or fault
bits. One way to eliminate the fault condition is for the
measured temperature to drop below the temperature
threshold minus the hysteresis value. Another way to
eliminate the fault condition is by writing new values for
the OVERT1 threshold or hysteresis so that a fault condition is no longer present. Note that the status byte
does not provide status of OVERT2.
The MAX6657/MAX6658/MAX6659 incorporate collision
avoidance so that completely asynchronous operation
is allowed between SMBus operations and temperature
conversions.
When autoconverting, if the THIGH and TLOW limits are
close together, it’s possible for both high-temp and lowtemp status bits to be set, depending on the amount of
time between status read operations. In these circumstances, it is best not to rely on the status bits to indicate reversals in long-term temperature changes.
Instead, use a current temperature reading to establish
the trend direction.
Conversion Rate Byte
The Conversion Rate register (Table 7) programs the
time interval between conversions in free-running
autonomous mode (RUN/STOP = 0). This variable rate
Table 6. Status Register Bit Assignments
BIT
NAME
POR STATE
7 (MSB)
BUSY
1
A/D is busy converting when high.
FUNCTION
6
LHIGH
0
Internal high-temperature alarm has tripped when high; cleared by POR or readout of
the Status register if the fault condition no longer exists.
5
LLOW
0
Internal low-temperature alarm has tripped when high; cleared by POR or readout of
the Status register if the fault condition no longer exists.
4
RHIGH
0
External high-temperature alarm has tripped when high; cleared by POR or readout of
the Status register if the fault condition no longer exists.
3
RLOW
0
External low-temperature alarm has tripped when high; cleared by POR or readout of
the Status register if the fault condition no longer exists.
2
OPEN
0
A high indicates an external diode open; cleared by POR or readout of the Status
register if the fault condition no longer exists.
1
EOT1
0
A high indicates the external junction temperature exceeds the external OVERT1
threshold.
0
IOT1
0
A high indicates the internal junction temperature exceeds the internal OVERT1
threshold.
______________________________________________________________________________________
13
MAX6657/MAX6658/MAX6659
Status Byte Functions
The status byte (Table 6) indicates which (if any) temperature thresholds have been exceeded. This byte also
indicates whether the ADC is converting and if there is
an open-circuit fault detected with the external sense
junction. After POR, the normal state of the MSB is 1 and
all the other flag bits are 0, assuming no alert or
overtemperature conditions are present. Bits 2 through
6 of the Status register are cleared by any successful
read of the Status register, unless the fault persists. The
MAX6657/MAX6658/MAX6659
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
Table 8. Slave Address Decoding for
MAX6659
Table 7. Conversion-Rate
Control Byte
DATA
CONVERSION RATE (Hz)
ADD CONNECTION
ADDRESS
00h
0.0625
GND
1001100
01h
0.125
VCC
1001110
02h
0.25
Floating
1001101
03h
0.5
04h
1
05h
2
06h
4
07h
8
08h
16
09h
16
0Ah-FFh
Reserved
Note: Extended resolution applies only for conversion rates of
4Hz or slower.
control can be used to reduce the supply current in
portable-equipment applications. The conversion rate
byte’s POR state is 08h (16Hz). The MAX6657/
MAX6658/MAX6659 use only the 4 least-significant bits
(LSBs) of this register. The 4 most-significant bits
(MSBs) are “don’t care” and should be set to zero when
possible. The conversion rate tolerance is ±25% at any
rate setting.
Valid A/D conversion results for both channels are
available one total conversion time (125ms nominal,
156ms maximum) after initiating a conversion, whether
conversion is initiated through the RUN/STOP bit, hardware STBY pin, one-shot command, or initial power-up.
Slave Addresses
The MAX6657/MAX6658 have a fixed address of
1001100. The MAX6659 can be programmed to have
one of three different addresses, allowing up to three
devices to reside on the same bus without address
conflicts. Table 8 lists address information.
The address pin state is checked at POR only, and the
address data stays latched to reduce quiescent supply
current due to the bias current needed for high-Z state
detection.
The MAX6657/MAX6658/MAX6659 also respond to the
SMBus Alert Response slave address (see Alert
Response Address section).
POR and UVLO
The MAX6657/MAX6658/MAX6659 have a volatile
memory. To prevent unreliable power-supply conditions
14
from corrupting the data in memory and causing erratic
behavior, a POR voltage detector monitors VCC and
clears the memory if VCC falls below 1.7V (typ, see
Electrical Characteristics). When power is first applied
and VCC rises above 2.0V (typ), the logic blocks begin
operating, although reads and writes at V CC levels
below 3.0V are not recommended. A second VCC comparator and the ADC undervoltage lockout (UVLO)
comparator prevent the ADC from converting until there
is sufficient headroom (VCC = +2.8V typ).
Power-Up Defaults
Power-up defaults include:
• ADC begins autoconverting at a 16Hz rate (legacy
resolution).
•
THIGH and TLOW registers are set to default limits,
respectively.
•
Interrupt latch is cleared.
•
Address-select pin is sampled (MAX6659 only).
•
Command register is set to 00h to facilitate quick
internal Receive Byte queries.
•
Hysteresis is set to 10°C.
•
Transistor type is set to a substrate or common collector PNP.
Table 9. Read Format for Alert Response
Address (000 1100)
BIT
NAME
7 (MSB)
ADD7
6
ADD6
5
ADD5
4
ADD4
3
ADD3
2
ADD2
1
ADD1
0 (LSB)
1
FUNCTION
Provide the current
MAX6659 slave address
that was latched at POR
(Table 8)
Logic 1
______________________________________________________________________________________
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
3.3V
0.1µF
200Ω
10kΩ
EACH
DXP
VCC
(STBY)
SMBDATA
DXN
DATA
CLOCK
SMBCLK
2200pF
MAX6657
MAX6658
MAX6659
µP
INTERRUPTED TO µP
ALERT
TO FAN DRIVER
OVERT1
(OVERT2)
(ADD)
TO SYSTEM SHUTDOWN
GND
() ARE MAX6659 ONLY
Chip Information
TRANSISTOR COUNT: 16,989
PROCESS: BiCMOS
______________________________________________________________________________________
15
MAX6657/MAX6658/MAX6659
Typical Operating Circuit
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
SOICN.EPS
MAX6657/MAX6658/MAX6659
Package Information
16
______________________________________________________________________________________
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
QSOP.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
17 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX6657/MAX6658/MAX6659
Package Information (continued)