MAX6695 [MAXIM]
Dual Remote/Local Temperature Sensors with SMBus Serial Interface; 双路远端/本地温度传感器，带有SMBus串行接口
| 型号： | MAX6695 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Dual Remote/Local Temperature Sensors with SMBus Serial Interface |
| 文件： | 总20页 (文件大小：192K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3183; Rev 1; 5/04
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
Ge n e ra l De s c rip t io n
Fe a t u re s
The MAX6695/MAX6696 are precise, dual-remote, and
local digital temperature sensors. They accurately mea-
sure the temperature of their own die and two remote
diode-connected transistors, and report the tempera-
ture in digital form on a 2-wire serial interface. The
remote diode is typically the emitter-base junction of a
common-collector PNP on a CPU, FPGA, GPU, or ASIC.
♦ Measure One Local and Two Remote
Temperatures
♦ 11-Bit, 0.125°C Resolution
♦ High Accuracy ±1.5°C (max) from +60°C to +100°C
(Remote)
♦ ACPI Compliant
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 MAX6695/MAX6696 can func-
tion autonomously with a programmable conversion
rate, which allows control of supply current and temper-
ature update rate to match system needs. For conver-
s ion ra te s of 2Hz or le s s , the te mp e ra ture is
re p re s e nte d a s 10 b its + s ig n with a re s olution of
+0.125°C. When the conversion rate is 4Hz, output data
is 7 bits + sign with a resolution of +1°C. The MAX6695/
MAX6696 also include an SMBus timeout feature to
enhance system reliability.
♦ Programmable Under/Overtemperature Alarms
♦ Programmable Conversion Rate
♦ Three Alarm Outputs: ALERT, OT1, and OT2
♦ SMBus/I2C™-Compatible Interface
Ord e rin g In fo rm a t io n
PART
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
10 µMAX
MAX6695AUB
MAX6696AEE
Remote temperature sensing accuracy is ±1.5°C be-
tween +60°C and +100°C with no calibration needed.
The MAX6695/MAX6696 measure temperatures from
-40°C to +125°C. In addition to the SMBus ALERT out-
put, the MAX6695/MAX6696 feature two overtempera-
ture limit indicators (OT1 and OT2), which are active
only while the temperature is above the corresponding
programmable temperature limits. The OT1 and OT2
outputs are typically used for fan control, clock throt-
tling, or system shutdown.
16 QSOP
Typ ic a l Op e ra t in g Circ u it
+3.3V
0.1µF
47Ω
10kΩ
EACH
The MAX6695 ha s a fixe d SMBus a d d re s s . The
MAX6696 ha s nine d iffe re nt p in-s e le c ta b le SMBus
a d d re s s e s . The MAX6695 is a va ila b le in a 10-p in
µMAX® and the MAX6696 is available in a 16-pin QSOP
package. Both operate throughout the -40°C to +125°C
temperature range.
V
CC
CPU
DXP1
SMBDATA
SMBCLK
DATA
CLOCK
INTERRUPT
TO µP
ALERT
MAX6695
TO CLOCK
THROTTLING
OT1
OT2
Ap p lic a t io n s
Notebook Computers
DXN
TO SYSTEM
SHUTDOWN
Desktop Computers
DXP2
Servers
GND
Workstations
GRAPHICS
PROCESSOR
Test and Measurement Equipment
Typical Operating Circuits continued at end of data sheet.
Pin Configurations appear at end of data sheet.
SMBus is a trademark of Intel Corp.
2
2
I C is a trademark of Philips Corp. Purchase of I C components
from Maxim Integrated Products, Inc., or one of its sublicensed
Associated Companies, conveys a license under the Philips
µMAX is a registered trademark of Maxim Integrated Products, Inc.
2
2
I C Patent Rights to use these components in an I C system,
2
provided that the system conforms to the I C Standard
Specification as defined by Philips.
________________________________________________________________ Maxim Integrated Products
1
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.
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
ABSOLUTE MAXIMUM RATINGS
V
CC
...........................................................................-0.3V to +6V
Continuous Power Dissipation (T = +70°C)
A
DXP1, DXP2................................................-0.3V to (V + 0.3V)
10-Pin mMAX (derate 6.9mW/°C above +70°C) .......555.6mW
16-Pin QSOP (derate 8.3mW/°C above +70°C) .......666.7mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature .....................................................+150°C
Storage Temperature Range ............................-65°C to +150°C
Lead Temperature (soldering, 10s) ................................+300°C
CC
DXN ......................................................................-0.3V to +0.8V
SMBCLK, SMBDATA, ALERT...................................-0.3V to +6V
RESET, STBY, ADD0, ADD1, OT1, OT2...................-0.3V to +6V
SMBDATA Current .................................................1mA to 50mA
DXN Current ......................................................................±1mA
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
(V = +3.0V to +3.6V, T = 0°C to +125°C, unless otherwise noted. Typical values are at V = +3.3V and T = +25°C)
CC
A
CC
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
3.6
10
UNITS
V
Supply Voltage
V
CC
3.0
Standby Supply Current
Operating Current
SMBus static, ADC in idle state
Interface inactive, ADC active
Conversion rate = 0.125Hz
Conversion rate = 1Hz
µA
0.5
35
1
mA
70
Average Operating Current
250
500
500
1000
µA
°C
Conversion rate = 4Hz
T
= +25°C to +100°C
(T = +45°C to +85°C)
RJ
-1.5
+1.5
A
Remote Temperature Error
(Note 1)
T
RJ
= 0°C to +125°C (T = +25°C to +100°C)
-3.0
-5.0
+3.0
+5.0
A
T
RJ
= -40°C to +125°C (T = 0°C to +125°C)
A
T
RJ
= -40°C to +125°C (T = -40°C)
A
+3.0
T
= +45°C to +85°C
= +25°C to +100°C
= 0°C to +125°C
= -40°C to +125°C
-2.0
-3.0
-4.5
+2.0
+3.0
+4.5
A
T
A
Local Temperature Error
°C
T
A
T
A
+3.0
1.45
500
2.8
Power-On Reset Threshold
V
, falling edge (Note 2)
1.3
2.2
1.6
V
mV
V
CC
POR Threshold Hysteresis
Undervoltage Lockout Threshold
Undervoltage Lockout Hysteresis
UVLO
Falling edge of V disables ADC
CC
2.95
90
mV
Channel 1 rate ≤4Hz, channel 2 / local rate
≤2Hz (conversion rate register ≤05h)
112.5
56.25
125
137.5
68.75
Conversion Time
ms
µA
Channel 1 rate ≥8Hz, channel 2 / local rate
≥4Hz (conversion rate register ≥06h)
62.5
High level
Low level
80
8
100
10
120
12
Remote-Diode Source Current
I
RJ
ALERT, OT1, OT2
Output Low Sink Current
Output High Leakage Current
INPUT PIN, ADD0, ADD1 (MAX6696)
Logic Input Low Voltage
V
= 0.4V
= 3.6V
6
1
mA
µA
OL
V
OH
V
0.3
V
V
IL
Logic Input High Voltage
V
IH
2.9
2
_______________________________________________________________________________________
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
ELECTRICAL CHARACTERISTICS (continued)
(V = +3.0V to +3.6V, T = 0°C to +125°C, unless otherwise noted. Typical values are at V = +3.3V and T = +25°C)
CC
A
CC
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
INPUT PIN, RESET, STBY (MAX6696)
Logic Input Low Voltage
V
0.8
V
V
IL
Logic Input High Voltage
V
IH
2.1
-1
Input Leakage Current
I
+1
µA
LEAK
SMBus INTERFACE (SMBCLK, SMBDATA, STBY)
Logic Input Low Voltage
Logic Input High Voltage
Input Leakage Current
Output Low Sink Current
Input Capacitance
V
0.8
V
V
IL
V
IH
2.1
I
V
= GND or V
= 0.6V
±1
6
µA
mA
pF
LEAK
IN
CC
I
OL
V
OL
C
5
IN
SMBus-COMPATIBLE TIMING (Figures 4 and 5) (Note 2)
Serial Clock Frequency
f
10
100
kHz
µs
SCL
Bus Free Time Between STOP
and START Condition
t
4.7
BUF
Repeat START Condition Setup
Time
t
90% of SMBCLK to 90% of SMBDATA
4.7
µs
SU:STA
START Condition Hold Time
STOP Condition Setup Time
Clock Low Period
Clock High Period
Data Setup Time
t
t
10% of SMBDATA to 90% of SMBCLK
90% of SMBCLK to 90% of SMBDATA
10% to 10%
4
4
µs
µs
µs
µs
µs
µs
µs
ns
ms
HD:STA
SU:STO
t
4
LOW
t
90% to 90%
4.7
250
300
HIGH
t
SU:DAT
HD:DAT
Data Hold Time
t
SMB Rise Time
t
1
R
SMB Fall Time
t
300
40
F
SMBus Timeout
SMBDATA low period for interface reset
20
30
Note 1: Based on diode ideality factor of 1.008.
Note 2: Specifications are guaranteed by design, not production tested.
_______________________________________________________________________________________
3
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V = 3.3V, T = +25°C, unless otherwise noted.)
CC
A
AVERAGE OPERATING SUPPLY CURRENT
vs. CONVERSION RATE CONTROL REGISTER VALUE
600
TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
5
4
6
5
4
3
2
1
0
500
400
300
200
100
0
3
REMOTE CHANNEL1
REMOTE CHANNEL2
2
1
0
-1
-2
-3
-4
-5
0
1
2
3
4
5
6
7
-50 -25
0
25
50
75 100 125
3.0
3.1
3.2
3.3
3.4
3.5
3.6
REMOTE TEMPERATURE (°C)
CONVERSION RATE CONTROL REGISTER VALUE (hex)
SUPPLY VOLTAGE (V)
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
TEMPERATURE ERROR
vs. DIFFERENTIAL NOISE FREQUENCY
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
5
4
3
3
2
V
= 10mV
P-P
IN
REMOTE CHANNEL2
REMOTE CHANNEL1
2
1
3
REMOTE CHANNEL2
REMOTE CHANNEL1
2
1
1
0
0
0
-1
-2
-3
-4
-5
-1
-1
-2
-3
-2
-3
-50 -25
0
25
50
75 100 125
0.001 0.01
0.1
1
10
100
1
10
100
DIE TEMPERATURE (°C)
FREQUENCY (MHz)
DXP-DXN CAPACITANCE (nF)
REMOTE TEMPERATURE ERROR
LOCAL TEMPERATURE ERROR
TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
vs. POWER-SUPPLY NOISE FREQUENCY
vs. COMMON-MODE NOISE FREQUENCY
3
3
3
2
1
100mV
P-P
10mV
P-P
100mV
P-P
2
2
1
REMOTE CHANNEL2
REMOTE CHANNEL1
REMOTE CHANNEL2
REMOTE CHANNEL1
1
0
0
0
-1
-2
-1
-1
-2
-2
-3
-3
-3
0.001
0.01
0.1
1
10
100
0.001
0.01
0.1
1
10
100
0.001
0.01
0.1
1
10
100
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (Hz)
4
_______________________________________________________________________________________
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
P in De s c rip t io n
PIN
NAME
FUNCTION
MAX6695
MAX6696
Supply Voltage Input, +3V to +3.6V. Bypass to GND with a 0.1µF capacitor. A
47Ω series resistor is recommended but not required for additional noise
filtering. See Typical Operating Circuit.
1
2
V
CC
Combined Remote-Diode Current Source and A/D Positive Input for Remote-
Diode Channel 1. DO NOT LEAVE DXP1 FLOATING; connect DXP1 to DXN if no
remote diode is used. Place a 2200pF capacitor between DXP1 and DXN for
noise filtering.
2
3
4
5
3
4
DXP1
DXN
DXP2
OT1
Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally
biased to one diode drop above ground.
Combined Remote-Diode Current Source and A/D Positive Input for Remote-
Diode Channel 2. DO NOT LEAVE DXP2 FLOATING; connect DXP2 to DXN if no
remote diode is used. Place a 2200pF capacitor between DXP2 and DXN for
noise filtering.
5
Overtemperature Active-Low Output, Open Drain. OT1 is asserted low only when
the temperature is above the programmed OT1 threshold.
10
6
7
8
9
GND
Ground
SMBCLK
SMBus Serial-Clock Input
SMBus Alert (Interrupt) Active-Low Output, Open-Drain. Asserts when
temperature exceeds user-set limits (high or low temperature) or when a remote
sensor opens. Stays asserted until acknowledged by either reading the status
register or by successfully responding to an alert response address. See the
ALERT Interrupts section.
8
11
ALERT
9
12
13
SMBDATA
OT2
SMBus Serial-Data Input/Output, Open Drain
Overtemperature Active-Low Output, Open Drain. OT2 is asserted low only when
temperature is above the programmed OT2 threshold.
10
—
—
1, 16
6
N.C.
No Connect
SMBus Slave Address Select Input (Table 10). ADD0 and ADD1 are sampled
upon power-up.
ADD1
Reset Input. Drive RESET high to set all registers to their default values (POR
state). Pull RESET low for normal operation.
—
—
—
7
RESET
ADD0
STBY
SMBus Slave Address Select Input (Table 10). ADD0 and ADD1 are sampled
upon power-up.
14
15
Hardware Standby Input. Pull STBY low to put the device into standby mode.
All registers’ data are maintained.
_______________________________________________________________________________________
5
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
Remote 2. Therefore, the Remote 1 conversion rate is
double that of the conversion rate for either of the other
The MAX6695/MAX6696 a re te mp e ra ture s e ns ors
two channels.
De t a ile d De s c rip t io n
designed to work in conjunction with a microprocessor
A BUSY status bit in status register 1 (see Table 7 and
the Sta tus Byte Func tions s e c tion) s hows tha t the
device is actually performing a new conversion. The
results of the previous conversion sequence are always
available when the ADC is busy.
or other intelligence in temperature monitoring, protec-
tion, or control applications. Communication with the
MAX6695/MAX6696 occurs through the SMBus serial
interface and dedicated alert pins. The overtempera-
ture alarms OT1 and OT2 are asserted if the software-
programmed temperature thresholds are exceeded.
OT1 and OT2 can be connected to a fan, system shut-
down, or other thermal-management circuitry.
Re m o t e -Dio d e S e le c t io n
The MAX6695/MAX6696 can directly measure the die
temperature of CPUs and other ICs that have on-board
temperature-sensing diodes (see the Typical Operating
Circuit) or they can measure the temperature of a dis-
crete diode-connected transistor.
The MAX6695/MAX6696 convert temperatures to digital
data continuously at a programmed rate or by selecting
a single conversion. At the highest conversion rate,
temperature conversion results are stored in the “main”
temperature data registers (at addresses 00h and 01h)
as 7-bit + sign data with the LSB equal to 1°C. At slow-
er conversion rates, 3 additional bits are available at
addresses 11h and 10h, providing 0.125°C resolution.
See Tables 2, 3, and 4 for data formats.
Effect of Ideality Factor
The accuracy of the remote temperature measurements
depends on the ideality factor (n) of the remote “diode”
(actually a transistor). The MAX6695/MAX6696 are opti-
mized for n = 1.008. A thermal diode on the substrate of
an IC is normally a PNP with its collector grounded. DXP_
must be connected to the anode (emitter) and DXN must
be connected to the cathode (base) of this PNP.
ADC a n d Mu lt ip le x e r
The MAX6695/MAX6696 averaging ADC (Figure 1) inte-
grates over a 62.5ms or 125ms period (each channel,
typ), depending on the conversion rate (see Electrical
Characteristics table). The use of an averaging ADC
attains excellent noise rejection.
If a sense transistor with an ideality factor other than
1.008 is used, the output data will be different from the
d a ta ob ta ine d with the op timum id e a lity fa c tor.
Fortunately, the difference is predictable. Assume a
remote-diode sensor designed for a nominal ideality
The MAX6695/MAX6696 multiplexer (Figure 1) automat-
ically steers bias currents through the remote and local
diodes. The ADC and associated circuitry measure
each diode’s forward voltages and compute the tem-
perature based on these voltages. If a remote channel
is not used, connect DXP_ to DXN. Do not leave DXP_
and DXN unconnected. When a conversion is initiated,
all channels are converted whether they are used or
factor n
is used to measure the temperature of
NOMINAL
a diode with a different ideality factor n . The measured
1
temperature T can be corrected using:
M
⎛
⎞
n
1
T = T
×
M
ACTUAL
⎜
⎟
n
⎝
⎠
NOMINAL
not. The DXN input is biased at one V above ground
BE
whe re te mp e ra ture is me a s ure d in Ke lvin a nd
for the MAX6695/MAX6696 is 1.008.
by an internal diode to set up the ADC inputs for a dif-
ferential measurement. Resistance in series with the
remote diode causes about +1/2°C error per ohm.
n
NOMIMAL
As an example, assume you want to use the MAX6695
or MAX6696 with a CPU that has an ideality factor of
1.002. If the diode has no series resistance, the mea-
sured data is related to the real temperature as follows:
A/D Co n ve rs io n S e q u e n c e
A conversion sequence consists of a local temperature
measurement and two remote temperature measure-
ments. Each time a conversion begins, whether initiat-
ed automatically in the free-running autoconvert mode
(RUN/STOP = 0) or by writing a one-shot command, all
three channels are converted, and the results of the
three measurements are available after the end of con-
version. Because it is common to require temperature
measurements to be made at a faster rate on one of the
remote channels than on the other two channels, the
conversion sequence is Remote 1, Local, Remote 1,
⎛
⎞
n
1.008
1.002
⎛
⎞
NOMINAL
T
= T
×
= T
×
= T × 1.00599
(
)
⎜
⎝
⎟
⎠
ACTUAL
M
M
M
⎜
⎟
n
1
⎝
⎠
For a real temperature of +85°C (358.15K), the measured
temperature is +82.87°C (356.02K), an error of -2.13°C.
Effect of Series Resistance
Series resistance (R ) with a sensing diode contributes
S
additional error. For nominal diode currents of 10µA
6
_______________________________________________________________________________________
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
V
CC
(RESET)
RESET/
UVLO
CIRCUITRY
3
MUX
DXP1
REMOTE1
REMOTE2
DXN
DXP2
CONTROL
LOGIC
(STBY)
ADC
LOCAL
DIODE FAULT
SMBus
8
8
SMBDATA
SMBCLK
READ
ALERT
S
WRITE
7
Q
R
REGISTER BANK
COMMAND BYTE
REMOTE TEMPERATURES
LOCAL TEMPERATURES
ALERT THRESHOLD
(ADD0)
(ADD1)
ADDRESS
DECODER
OT1
OT2
S
Q
R
ALERT RESPONSE ADDRESS
OT1 THRESHOLDS
S
R
Q
OT2 THRESHOLDS
() ARE FOR MAX6696 ONLY.
Figure 1. MAX6695/MAX6696 Functional Diagram
and 100µA, the change in the measured voltage due to
series resistance is:
Assume that the sensing diode being measured has a
series resistance of 3Ω. The series resistance con-
tributes a temperature offset of:
∆V = (100µA−10µA) ×R = 90µA×R
S
M
S
°C
3Ω × 0.453
= +1.36°C
Ω
Since 1°C corresponds to 198.6µV, series resistance
contributes a temperature offset of:
The effects of the ideality factor and series resistance
are additive. If the diode has an ideality factor of 1.002
and series resistance of 3Ω, the total offset can be cal-
culated by adding error due to series resistance with
error due to ideality factor:
µV
Ω
90
°C
Ω
= 0.453
µV
°C
198.6
1.36°C - 2.13°C = -0.77°C
for a diode temperature of +85°C.
_______________________________________________________________________________________
7
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
In this example, the effect of the series resistance and
the ideality factor partially cancel each other.
Table 1. Remote-Sensor Transistor
Manufacturers
Discrete Remote Diodes
MANUFACTURER
MODEL NO.
When the remote-sensing diode is a discrete transistor,
its collector and base must be connected together.
Table 1 lists examples of discrete transistors that are
appropriate for use with the MAX6695/MAX6696.
Central Semiconductor (USA) CMPT3904
Rohm Semiconductor (USA)
Samsung (Korea)
SST3904
KST3904-TF
SMBT3904
Siemens (Germany)
Zetex (England)
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, the 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 < ß <150, for
e xa mp le ) ind ic a te tha t the ma nufa c ture r ha s g ood
process controls and that the devices have consistent
FMMT3904CT-ND
Note: Discrete transistors must be diode connected (base
shorted to collector).
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 local temperature mea-
surements, the worst-case error occurs when autocon-
verting at the fastest rate and simultaneously sinking
maximum current at the ALERT output. For example,
V
BE
characteristics.
Manufacturers of discrete transistors do not normally
specify or guarantee ideality factor. This is normally not
a problem since good-quality discrete transistors tend
to have ideality factors that fall within a relatively narrow
range. We have observed variations in remote tempera-
ture readings of less than 2°C with a variety of dis-
crete transistors. Still, it is good design practice to
verify good consistency of temperature readings with
s e ve ra l d is c re te tra ns is tors from a ny ma nufa c ture r
under consideration.
with V
= 3.6V, a 4Hz conversion rate and ALERT
CC
sinking 1mA, the typical power dissipation is:
V
× 500µA+ 0.4V×1mA = 2.2mW
CC
θ
for the 16-pin QSOP package is about +120°C/W,
so assuming no copper PC board heat sinking, the
resulting temperature rise is:
J-A
∆T = 2.2mW×120°C / W = 0.264°C
Th e rm a l Ma s s a n d S e lf-He a t in g
When sensing local temperature, these temperature
sensors are intended to measure the temperature of the
PC board to which they are soldered. The leads pro-
vide a good thermal path between the PC board traces
and the die. As with all IC temperature sensors, thermal
conductivity between the die and the ambient air is
poor by comparison, making air temperature measure-
ments impractical. Because the thermal mass of the PC
b oa rd is fa r g re a te r tha n tha t of the MAX6695/
MAX6696, the device follows temperature changes on
the PC board with little or no perceivable delay.
Even under these worst-case circumstances, it is diffi-
cult to introduce significant self-heating errors.
ADC No is e Filt e rin g
The integrating ADC has good noise rejection for low-
frequency signals such as power-supply hum. In envi-
ronments with significant high-frequency EMI, connect
an external 2200pF capacitor between DXP_ and DXN.
Larger capacitor values can be used for added filter-
ing, but do not exceed 3300pF because it can intro-
duce errors due to the rise time of the switched current
source. High-frequency noise reduction is needed for
high-accuracy remote measurements. Noise can be
reduced with careful PC board layout as discussed in
the PC Board Layout section.
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.
Whe n me a s uring te mp e ra ture with d is c re te re mote
tra ns is tors , the b e s t the rma l re s p ons e time s a re
obtained with transistors in small packages (i.e., SOT23
or SC70). Take care to account for thermal gradients
between the heat source and the sensor, and ensure
Lo w -P o w e r S t a n d b y Mo d e
Standby mode reduces the supply current to less than
10µA by disabling the ADC. Enter hardware standby
(MAX6696 only) by forcing STBY low, or enter software
standby by setting the RUN/STOP bit to 1 in the config-
8
_______________________________________________________________________________________
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
Writ e Byt e Fo rm a t
ADDRESS
7 bits
S
WR
ACK
COMMAND
ACK
DATA
ACK
P
8 bits
8 bits
1
Slave Address: equiva-
lent to chip-select line of
a 3-wire interface
Command Byte: selects which
register you are writing to
Data Byte: data goes into the register
s e t b y the c omma nd b yte (to s e t
thresholds, configuration masks, and
sampling rate)
Re a d Byt e Fo rm a t
ADDRESS
WR
ACK
COMMAND
ACK
S
ADDRESS
RD
ACK
DATA
///
P
7 bits
8 bits
7 bits
8 bits
Sla ve Ad d re s s : e q uiva -
lent to chip-select line
Command Byte: selects
which register you are
reading from
Slave Address: repeated
due to change in data-
flow direction
Data Byte: reads from
the register set by the
command byte
S e n d Byt e Fo rm a t
ADDRESS WR ACK COMMAND ACK
Re c e ive Byt e Fo rm a t
P
S
ADDRESS
RD
ACK DATA
8 bits
///
P
7 bits
8 bits
7 bits
Data Byte: reads data from
the re g is te r c omma nd e d
by the last Read Byte or
Write Byte tra ns mis s ion;
also used for SMBus Alert
Response return address
Command Byte: sends com-
mand with no data, usually
used for one-shot command
S = Start condition
P = Stop condition
Shaded = Slave transmission
/// = Not acknowledged
Figure 2. SMBus Protocols
uration byte register. Hardware and software standbys
are very similar; all data is retained in memory, and the
SMBus interface is alive and listening for SMBus com-
mands but the SMBus timeout is disabled. The only dif-
ference is that in software standby mode, the one-shot
command initiates a conversion. With hardware stand-
by, the one-shot command is ignored. Activity on the
SMBus causes the device to draw extra supply current.
The MAX6695/MAX6696 employ four standard SMBus
p rotoc ols : Write Byte , Re a d Byte , Se nd Byte , a nd
Receive Byte (Figure 2). The shorter Receive Byte proto-
col allows quicker transfers, provided that the correct
data register was previously selected by a Read Byte
instruction. Use caution with the shorter protocols in mul-
timaster systems, since a second master could overwrite
the command byte without informing the first master.
Driving STBY low overrides any software conversion
command. If a hardware or software standby command
is received while a conversion is in progress, the con-
version cycle is interrupted, and the temperature regis-
ters are not updated. The previous data is not changed
and remains available.
When the conversion rate control register is set ≥ 06h,
temperature data can be read from the read internal
temperature (00h) and read external temperature (01h)
registers. The temperature data format in these regis-
ters is 7 bits + sign in two’s-complement form for each
channel, with the LSB representing 1°C (Table 2). The
MSB is transmitted first. Use bit 3 of the configuration
register to select the registers corresponding to remote
1 or remote 2.
S MBu s Dig it a l In t e rfa c e
From a software perspective, the MAX6695/MAX6696
appear as a series of 8-bit registers that contain tem-
perature 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
a nd a la rm thre s hold d a ta . The s a me SMBus s la ve
address provides access to all functions.
When the conversion rate control register is set ≤ 05h,
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 register (10h) and read internal
_______________________________________________________________________________________
9
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
extended temperature register (11h) (Table 3), which
extends the temperature data to 10 bits + sign and the
Table 2. Data Format (Two’s Complement)
TEMP (°C)
+130.00
+127.00
+126.00
+25.25
+0.50
0
DIGITAL OUTPUT
0 111 1111
0 111 1111
0 111 1110
0 001 1001
0 000 0001
0 000 0000
1 111 1111
1 100 1001
resolution to +0.125°C per LSB (Table 4).
When a conversion is complete, the main register and
the extended register are updated almost simultane-
ous ly. Ens ure tha t no c onve rs ions a re c omp le te d
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 resolu-
tion te mp e ra ture d a ta us ing one of the following
approaches:
-1
-55
•
Put the MAX6695/MAX6696 into standby mode by
setting bit 6 of the configuration register to 1. Read
the contents of the data registers. Return to run
mode by setting bit 6 to zero.
Diode fault
(short or open)
1 000 0000
•
Put the MAX6695/MAX6696 into standby mode by
setting bit 6 of the configuration register to 1. Initiate
a one-shot conversion using Send Byte command
0Fh. When this conversion is complete, read the
contents of the temperature data registers.
Table 3. Extended Resolution Register
FRACTIONAL
CONTENTS OF
TEMPERATURE (°C)
EXTENDED REGISTER
0
000X XXXX
001X XXXX
010X XXXX
011X XXXX
100X XXXX
101X XXXX
110X XXXX
111X XXXX
Dio d e Fa u lt Ala rm
There is a continuity fault detector at DXP_ that detects
an open circuit between DXP_ and DXN, or a DXP_
+0.125
+0.250
+0.375
+0.500
+0.625
+0.750
+0.875
short to V , GND, or DXN. If an open or short circuit
CC
exists, the external temperature register (01h) is loaded
with 1000 0000. Bit 2 (diode fault) of the status registers
is correspondingly set to 1. The ALERT output asserts
for open diode faults but not for shorted diode faults.
Immediately after power-on reset (POR), the status reg-
ister indicates that no fault is present until the end of
the first conversion. After the conversion is complete,
any diode fault is indicated in the appropriate status
register. Reading the status register clears the diode
fault bit in that register, and clears the ALERT output if
set. If the diode fault is present after the next conver-
sion, the status bit will again be set and the ALERT out-
put will assert if the fault is an open diode fault.
Note: Extended resolution applies only for conversion rate
control register values of 05h or less.
Table 4. Data Format in Extended Mode
TEMP (°C)
+130.00
+127.00
+126.5
+25.25
+0.50
0
INTEGER TEMP
0 111 1111
0 111 1111
0 111 1110
0 001 1001
0 000 0000
0 000 0000
1 111 1111
1111 1111
FRACTIONAL TEMP
000X XXXX
000X XXXX
100X XXXX
010X XXXX
100X XXXX
000X XXXX
000X XXXX
010X XXXX
000X XXXX
Ala rm Th re s h o ld Re g is t e rs
Six registers, WLHO, WLLM, WRHA (1 and 2), and
WRLN (1 and 2), store ALERT threshold values. WLHO
and WLLM, are for internal ALERT high-temperature
a nd low-te mp e ra ture limits , re s p e c tive ly. Like wis e ,
WRHA and WRLN are for external channel 1 and chan-
ne l 2 high-te mpe ra ture a nd low-te mpe ra ture limits,
respectively (Table 5). If either measured temperature
equals or exceeds the corresponding ALERT threshold
value, the ALERT output is asserted. The POR state of
both internal and external ALERT high-temperature limit
registers is 0100 0110 or +70°C.
-1
-1.25
-55
1100 1001
10 ______________________________________________________________________________________
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
Table 5. Command-Byte Register Bit Assignments
REGISTER
ADDRESS
POR STATE
FUNCTION
0000 0000
(0°C)
RLTS
00 h
Read internal temperature
0000 0000
(0°C)
Read external channel 1 temperature if bit 3 of configuration register is 0;
Read external channel 2 temperature if bit 3 of configuration register is 1
RRTE
01 h
RSL1
RCL
02 h
03 h
04 h
1000 0000
0000 0000
0000 0110
Read status register 1
Read configuration byte (fault queue should be disabled at startup)
Read conversion rate byte
RCRA
0100 0110
(+70°C)
RLHN
RLLI
05 h
06 h
07 h
08 h
Read internal ALERT high limit
Read internal ALERT low limit
1100 1001
(-55°C)
0100 0110
(+70°C)
Read external channel 1 ALERT high limit if bit 3 of configuration register is 0;
Read external channel 2 ALERT high limit if bit 3 of configuration register is 1
RRHI
RRLS
1100 1001
(-55°C)
Read external channel 1 ALERT low limit if bit 3 of configuration register is 0;
Read external channel 2 ALERT low limit if bit 3 of configuration register is 1
WCA
09 h
0A h
0010 0000
0000 0110
Write configuration byte
WCRW
Write conversion rate byte
0100 0110
(+70°C)
WLHO
WLLM
WRHA
0B h
0C h
0D h
Write internal ALERT high limit
Write internal ALERT low limit
1100 1001
(-55°C)
0100 0110
(+70°C)
Write external channel 1 ALERT high limit if bit 3 of configuration register is 0;
Write external channel 2 ALERT high limit if bit 3 of configuration register is 1
1100 1001
(-55°C)
Write external channel 1 ALERT low limit if bit 3 of configuration register is 0;
Write external channel 2 ALERT low limit if bit 3 of configuration register is 1
WRLN
OSHT
REET
0E h
0F h
10 h
0000 0000
One shot
Read extended temp of external channel 1 if bit 3 of configuration register is 0;
Read extended temp of external channel 2 if bit 3 of configuration register is 1
0000 0000
RIET
RSL2
11 h
12 h
0000 0000
0000 0000
Read internal extended temperature
Read status register 2
0111 1000
(+120°C)
Read/write external OT2 limit for channel 1 if bit 3 of configuration register is 0;
Read/write external OT2 limit for channel 2 if bit 3 of configuration register is 1
RWO2E
RWO2I
RWO1E
RWO1I
16 h
17 h
19 h
20 h
0101 1010
(+90°C)
Read/write internal OT2 limit
0101 1010
(+90°C)
Read/write external OT1 limit for channel 1 if bit 3 of configuration register is 0;
Read/write external OT1 limit for channel 2 if bit 3 of configuration register is 1
0100 0110
(+70°C)
Read/write internal OT1 limit
______________________________________________________________________________________ 11
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
Table 5. Command-Byte Register Bit Assignments (continued)
REGISTER
ADDRESS
POR STATE
FUNCTION
Temperature hysteresis for OT1 and OT2
Read manufacturer ID
0000 1010
(10°C)
HYST
21 h
RDID
FE h
4D h
exists, the device reasserts the ALERT interrupt at the
end of the next conversion.
The POR state of both internal and external ALERT low-
temperature limit registers is 1100 1001 or -55°C. Use
bit 3 of the configuration register to select remote 1 or
remote 2 when reading or writing remote thresholds.
OT1 a n d OT2 Ove rt e m p e ra t u re Ala rm s
Two registers, RWO1E and RWO1I, store remote and
local alarm threshold data corresponding to the OT1
output. Two other registers, RWO2E and RWO2I, store
remote and local alarm threshold data corresponding
to the OT2 output. The values stored in these registers
are high-temperature thresholds. The OT1 or OT2 out-
put is asserted if any one of the measured tempera-
ture s e q ua ls or e xc e e d s the c orre s p ond ing a la rm
threshold value.
Additional registers, RWO1E, RWO1I, RWO2E, and
RWO2I, store remote and local alarm threshold data
information corresponding to the OT1 and OT2 outputs
(See the OT1 and OT2 Overtemperature Alarms section.)
ALERT In t e rru p t Mo d e
An ALERT interrupt occurs when the internal or external
temperature reading exceeds a high- or low-tempera-
ture limit (both limits are user programmable), or when
the remote diode is disconnected (for continuity fault
detection). The ALERT interrupt output signal is latched
and can be cleared only by reading either of the status
registers or by successfully responding to an Alert
Response address. 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
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 con-
version rate.
OT1 and OT2 always operate in comparator mode and
are asserted when the temperature rises above a value
programmed in the appropriate threshold register. They
are deasserted when the temperature drops below this
threshold, minus the programmed value in the hystere-
sis HYST register (21h). An overtemperature output can
be used to activate a cooling fan, send a warning, initi-
ate clock throttling, or trigger a system shutdown to
prevent component damage. The HYST byte sets the
amount of hysteresis to deassert both OT1 and OT2
outputs. The data format for the HYST byte is 7 bit +
sign with +1°C resolution. Bit 7 of the HYST register
should always be zero.
Ale rt Re s p o n s e Ad d re s s
The SMBus Alert Response interrupt pointer provides
quick fault identification for simple slave devices. Upon
re c e iving a n inte rrup t s ig na l, the hos t ma s te r c a n
broadcast a Receive Byte transmission to the Alert
Response slave address (see Slave Addresses sec-
tion). Then, any slave device that generated an inter-
rup t a tte mp ts to id e ntify its e lf b y p utting its own
address on the bus.
OT1 responds immediately to temperature faults. OT2
a c tiva te s e ithe r imme d ia te ly or a fte r four c ons e c u-
tive remote channel temperature faults, depending on
the state of the fault queue bit (bit 5 of the configura-
tion register).
Co m m a n d Byt e Fu n c t io n s
The 8-bit command byte register (Table 5) is the master
index that points to the various other registers within the
MAX6695/MAX6696. 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.
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
acknowledgement and continues to hold the ALERT
line low until cleared. (The conditions for clearing an
a le rt va ry d e p e nd ing on the typ e of s la ve d e vic e .)
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
On e -S h o t
The one-shot command immediately forces a new con-
version cycle to begin. If the one-shot command is
received when the MAX6695/MAX6696 are in software
standby mode (RUN/STOP bit = 1), a new conversion is
12 ______________________________________________________________________________________
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
Table 6. Configuration Byte Functions
POR
STATE
BIT
7(MSB)
6
NAME
MASK1
FUNCTION
0
Mask ALERT interrupts when 1.
Standby mode control bit. If 1, immediately stops converting and enters
standby mode. If zero, it converts in either one-shot or timer mode.
RUN/STOP
0
Fault queue enables when 1. When set to 1, four consecutive faults must occur
before OT2 output is asserted.
5
4
3
Fault Queue
RFU
0
0
0
Reserved.
0: Read/write remote 1 temperature and set-point values.
1: Read/write remote 2 temperature and set-point values.
Remote 2 Select
2
1
0
SMB Timeout Disable
MASK Alert Channel 2
MASK Alert Channel 1
0
0
0
When set to 1, it disables the SMBus timeout, as well as the alert response.
When set to 1, it masks ALERT interrupt due to channel 2.
When set to 1, it masks ALERT interrupt due to channel 1.
begun, after which the device returns to standby mode.
If a conversion is in progress when a one-shot com-
mand is received, the command is ignored. If a one-
s hot c omma nd is re c e ive d in a utoc onve rt mod e
(RUN/STOP bit = 0) between conversions, a new con-
version begins, the conversion rate timer is reset, and
the next automatic conversion takes place after a full
delay elapses.
S t a t u s Byt e Fu n c t io n s
The status registers (Tables 7 and 8) indicate which (if
any) temperature thresholds have been exceeded and
if there is an open-circuit fault detected with the exter-
nal sense junctions. Status register 1 also indicates
whether the ADC is converting. After POR, the normal
state of the registers’ bits is zero (except bit 7 of status
register 1), assuming no alert or overtemperature con-
ditions are present. Bits 0 through 6 of status register 1
and bits 1 through 7 of status register 2 are cleared by
any successful read of the status registers, unless the
fault persists. The 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.
Fa u lt Qu e u e Fu n c t io n
To avoid false triggering of the MAX6695/MAX6696 in
noisy environments, a fault queue is provided, which
can be enabled by setting bit 5 (configuration register)
to 1. Four channel 1 fault or two channel 2 fault events
must occur consecutively before the fault output (OT2)
becomes active. Any reading that breaks the sequence
resets the fault queue counter. If there are three over-
limit readings followed by a within-limit reading, the
remote channel 1 fault queue counter is reset.
The bits indicating OT1 and OT2 are cleared only on
reading status even if the fault conditions still exist.
Reading the status byte does not clear the OT1 and
OT2 outputs. One way to eliminate the fault condition is
for the measured temperature to drop below the tem-
perature threshold minus the hysteresis value. Another
way to eliminate the fault condition is by writing new
values for the RWO2E, RWO2I, RWO1E, RWO1I, or
HYST registers so that a fault condition is no longer
present.
Co n fig u ra t io n Byt e Fu n c t io n s
The configuration byte register (Table 6) is a read-write
register with several functions. Bit 7 is used to mask
(disable) ALERT interrupts. Bit 6 puts the device into
software standby mode (STOP) or autonomous (RUN)
mode. Bit 5, when 1, enables the Fault Queue. Bit 4 is
reserved. Bit 3 is used to select either remote channel 1
or remote channel 2 for reading temperature data or for
setting or reading temperature limits. Bit 2 disables the
SMBus timeout, as well as the Alert Response. Bit 1
masks ALERT interrupt due to channel 2 when high. Bit
0 masks ALERT interrupt due to channel 1 when high.
When autoconverting, if the T
and T
limits are
HIGH
LOW
close together, it is possible for both high-temp and
low-te mp s ta tus b its to b e s e t, d e p e nd ing on the
amount of time between Status Read operations. In
these circumstances, it is best not to rely on the status
b its to ind ic a te re ve rs a ls in long -te rm te mp e ra ture
changes. Instead, use a current temperature reading to
establish the trend direction.
______________________________________________________________________________________ 13
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
Table 7. Status Register 1 Bit Assignments
BIT
NAME
POR
FUNCTION
7(MSB)
BUSY
1
A/D is busy converting when 1.
When 1, internal high-temperature ALERT has tripped, cleared by POR or by reading this status
register. If the fault condition still exists, this bit is set again after the next conversion.
6
5
LHIGH
LLOW
0
0
When 1, internal low-temperature ALERT has tripped, cleared by POR or by reading this status
register. If the fault condition still exists, this bit is set again after the next conversion.
A 1 indicates external junction 1 high-temperature ALERT has tripped, cleared by POR or by
reading this status register. If the fault condition still exists, this bit is set again after the next
conversion.
4
R1HIGH
0
A 1 indicates external junction 1 low-temperature ALERT has tripped, cleared by POR or by reading this
status register. If the fault condition still exists, this bit is set again after the next conversion.
3
2
1
0
R1LOW
1OPEN
R1OT1
IOT1
0
0
0
0
A 1 indicates external diode 1 is open, cleared by POR or by reading this status register. If the
fault condition still exists, this bit is set again after the next conversion.
A 1 indicates external junction 1 temperature exceeds the OT1 threshold, cleared by reading this
register.
A 1 indicates internal junction temperature exceeds the internal OT1 threshold, cleared by
reading this register.
Table 8. Status Register 2 Bit Assignments
BIT
NAME
POR
FUNCTION
A 1 indicates internal junction temperature exceeds the internal OT2 threshold, cleared by
reading this register.
7(MSB)
IOT2
0
A 1 indicates external junction temperature 2 exceeds the external OT2 threshold, cleared by
reading this register.
6
5
4
3
2
R2OT2
R1OT2
0
0
0
0
0
A 1 indicates external junction temperature 1 exceeds the OT2 threshold, cleared by reading this
register.
A 1 indicates external junction 2 high-temperature ALERT has tripped; cleared by POR or readout
of the status register. If the fault condition still exists, this bit is set again after the next conversion.
R2HIGH
R2LOW
2OPEN
A 1 indicates external junction 2 low-temperature ALERT has tripped; cleared by POR or readout
of the status register. If the fault condition still exists, this bit is set again after the next conversion.
A 1 indicates external diode 2 open; cleared by POR or readout of the status register. If the fault
condition still exists, this bit is set again after the next conversion.
A 1 indicates external junction 2 temperature exceeds the OT1 threshold, cleared by reading this
register.
1
0
R2OT1
RFU
0
0
Reserved.
Re s e t (MAX6 6 9 6 On ly)
Co n ve rs io n Ra t e Byt e
The conversion-rate control register (Table 9) programs
the time interval between conversions in free-running
autonomous mode (RUN/STOP = 0). This variable rate
control can be used to reduce the supply current in
portable-equipment applications. The conversion rate
The MAX6696’s registers are reset to their power-on
values if RESET is driven high. When reset occurs, all
registers go to their default values, and the SMBus
address pins are sampled.
14 ______________________________________________________________________________________
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
Table 9. Conversion-Rate Control Register (POR = 0110)
CONVERSION
RATE (Hz) REMOTE
CHANNEL 2 AND
LOCAL
CONVERSION
PERIOD (s)
REMOTE CHANNEL REMOTE CHANNEL
CONVERSION
PERIOD (s)
CONVERSION RATE
(Hz) REMOTE
BIT 3
BIT 1
BIT0
HEX
CHANNEL 1
2 AND LOCAL
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
00h
01h
02h
03h
04h
05h
06h
07h
0.0625
0.125
16
8
8
4
0.125
0.25
0.5
1
0.25
0.5
1
4
2
2
1
2
1
0.5
0.25
0.125
0.125
2
4
0.5
0.25
0.25
4
8
4
8
Note: Extended resolution applies only for conversion rate control register values of 05h or less.
byte’s POR state is 06h (4Hz). The MAX6695/MAX6696
Table 10. POR Slave Address Decoding
(ADD0 and ADD1)
use only the 3 LSBs of the control register. The 5 MSBs
are don’t care and should be set to zero. The conver-
sion rate tolerance is ±25% at any rate setting.
ADD0
GND
ADD1
GND
ADDRESS
0011 000
0011 001
0011 010
0101 001
0101 010
0101 011
1001 100
1001 101
1001 110
Valid A/D conversion results for all channels are avail-
able one total conversion time after initiating a conver-
s ion, whe the r c onve rs ion is initia te d throug h the
RUN/STOP b it, ha rd wa re STBY p in, one -s hot c om-
mand, or initial power-up.
GND
High-Z
GND
V
CC
High-Z
High-Z
High-Z
GND
High-Z
S la ve Ad d re s s e s
The MAX6695 has a fixed address of 0011 000. The
MAX6696 device address can be set to any one of nine
different values at power-up by pin strapping ADD0
and ADD1 so that more than one MAX6695/MAX6696
can reside on the same bus without address conflicts
(Table 10).
V
CC
V
CC
GND
V
CC
High-Z
V
CC
V
CC
P o w e r-Up De fa u lt s
The address pin states are checked at POR and RESET
only, and the address data stays latched to reduce qui-
escent supply current due to the bias current needed for
hig h-imp e d a nc e s ta te d e te c tion. The MAX6695/
MAX6696 also respond to the SMBus Alert Response
slave address (see the Alert Response Address section).
•
•
•
Interrupt latch is cleared.
Address select pin is sampled.
ADC b e g ins a utoc onve rting a t a 4Hz ra te for
channel 2/local and 8Hz for channel 1.
•
•
•
Command register is set to 00h to facilitate quick
internal Receive Byte queries.
P OR a n d UVLO
To prevent unreliable power-supply conditions from
corrupting the data in memory and causing erratic
T
HIGH
and T
registers are set to default max
LOW
and min limits, respectively.
behavior, a POR voltage detector monitors V
and
CC
Hysteresis is set to 10°C.
clears the memory if V
falls below 1.45V (typ; see
CC
Electrical Characteristics). When power is first applied
and V rises above 2.0V (typ), the logic blocks begin
CC
operating, although reads and writes at V
levels
CC
below 3.0V are not recommended.
______________________________________________________________________________________ 15
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
A
B
C
D
E
F
G
H
I
J
K
L
M
t
t
HIGH
LOW
SMBCLK
SMBDATA
t
t
t
t
HD:DAT
HD:STA
SU:STA
SU:DAT
t
t
SU:STO
BUF
A = 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
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
M = NEW START CONDITION
E = SLAVE PULLS SMBDATA LINE LOW
Figure 3. SMBus Write Timing Diagram
A
B
C
D
E
F
G
H
I
J
K
L
M
t
t
HIGH
LOW
SMBCLK
SMBDATA
t
t
t
t
HD:DAT
HD:STA
SU:STA
SU:DAT
t
t
SU:STO
BUF
A = START CONDITION
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
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
M = NEW START CONDITION
E = SLAVE PULLS SMBDATA LINE LOW
Figure 4. SMBus Read Timing Diagram
2) 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.
P C Bo a rd La yo u t
Follow these guidelines to reduce the measurement
error when measuring remote temperature:
1) Place the MAX6695/MAX6696 as close as is practi-
cal 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
PCI buses.
3) Route the DXP and DXN traces in parallel and in
close proximity to each other. Each parallel pair of
traces (DXP1 and DXN or DXP2 and DXN) should go
to a remote diode. Connect the two DXN traces at
the MAX6695/MAX6696. Route these traces away
from any higher voltage traces, such as +12VDC.
16 ______________________________________________________________________________________
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
Tw is t e d -P a ir a n d S h ie ld e d Ca b le s
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
GND
10 mils
between 6ft and 12ft before noise introduces excessive
10 mils
DXP
e rrors . For long e r d is ta nc e s , the b e s t s olution is a
shielded twisted pair like that used for audio micro-
phones. For example, Belden #8451 works well for dis-
ta nc e s up to 100ft in a nois y e nvironme nt. At the
device, connect the twisted pair to DXP and DXN and
the shield to GND. Leave the shield unconnected at the
remote sensor.
MINIMUM
10 mils
10 mils
DXN
GND
Figure 5. Recommended DXP-DXN PC Traces
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 1Ω of series resistance the error is approxi-
mately +1/2°C.
Le a ka g e c urre nts from PC b oa rd c onta mina tion
must be dealt with carefully since a 20MΩ leakage
path from DXP to ground causes about +1°C error.
If hig h-volta g e tra c e s a re una void a b le , c onne c t
guard traces to GND on either side of the DXP-DXN
traces (Figure 5).
Ch ip In fo rm a t io n
TRANSISTOR COUNT: 22,964
4) Route through as few vias and crossunders as pos-
s ib le to minimize c op p e r/s old e r the rmoc oup le
effects.
PROCESS: BiCMOS
5) Use wide traces when practical.
6) When the power supply is noisy, add a resistor (up
to 47Ω) in series with V
(see Typical Operating
CC
Circuit).
Typ ic a l Op e ra t in g Circ u it s (c o n t in u e d )
+3.3V
0.1µF
47Ω
10kΩ
EACH
V
CPU
CC
STBY
DXP1
DXN
SMBDATA
SMBCLK
DATA
CLOCK
INTERRUPT
TO µP
ALERT
MAX6696
TO CLOCK
THROTTLING
OT1
OT2
TO SYSTEM
SHUTDOWN
DXP2
2N3906
ADD0 ADD1 GND RESET
______________________________________________________________________________________ 17
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
P in Co n fig u ra t io n s
TOP VIEW
N.C.
1
2
3
4
5
6
7
8
16 N.C.
V
15 STBY
14 ADD0
13 OT2
CC
DXP1
DXN
V
1
2
3
4
5
10 OT2
CC
MAX6696
DXP1
DXN
DXP2
OT1
9
8
7
6
SMBDATA
DXP2
ADD1
RESET
GND
12 SMBDATA
MAX6695
ALERT
SMBCLK
GND
ALERT
11
10 OT1
SMBCLK
9
µMAX
QSOP
18 ______________________________________________________________________________________
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
P a c k a g e In fo rm a t io n
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
e
4X S
10
10
INCHES
DIM MIN
MAX
MILLIMETERS
MIN
-
MAX
1.10
0.15
0.95
3.05
3.00
3.05
3.00
5.05
0.70
A
-
0.043
0.006
0.037
0.120
0.118
0.120
0.118
0.199
A1
A2
D1
D2
E1
E2
H
0.002
0.030
0.116
0.114
0.116
0.114
0.187
0.05
0.75
2.95
2.89
2.95
2.89
4.75
0.40
H
0 0.50±0.1
0.6±0.1
L
0.0157 0.0275
0.037 REF
L1
b
0.940 REF
0.007
0.0106
0.177
0.090
0.270
1
1
e
0.0197 BSC
0.500 BSC
0.6±0.1
c
0.0035 0.0078
0.0196 REF
0.200
BOTTOM VIEW
0.498 REF
S
TOP VIEW
α
0°
6°
0°
6°
D2
E2
GAGE PLANE
A2
c
A
E1
b
L
α
A1
D1
L1
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, 10L uMAX/uSOP
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0061
I
1
______________________________________________________________________________________ 19
Du a l Re m o t e /Lo c a l Te m p e ra t u re S e n s o rs w it h
S MBu s S e ria l In t e rfa c e
P a c k a g e In fo rm a t io n (c o n t in u e d )
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH
1
21-0055
E
1
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.
20 ____________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 4 0 8 -7 3 7 -7 6 0 0
© 2004 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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