MAX6695YAUB [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
MAX6695YAUB
型号: MAX6695YAUB
厂家: MAXIM INTEGRATED PRODUCTS    MAXIM INTEGRATED PRODUCTS
描述:

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

传感器 换能器 温度传感器 输出元件 信息通信管理
文件: 总19页 (文件大小:237K)
中文:  中文翻译
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19-3183; Rev 3; 4/11  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
5/MAX96  
General Description  
Features  
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-  
sion rates of 2Hz or less, the temperature is  
represented as 10 bits + sign with a resolution 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  
Compatible with 65nm Process Technology  
(Y Versions)  
Ordering Information  
PART  
TEMP RANGE  
-40°C to +125°C  
-40°C to +125°C  
-40°C to +125°C  
-40°C to +125°C  
PIN-PACKAGE  
10 μMAX  
MAX6695AUB+  
MAX6695YAUB+  
MAX6696AEE+  
MAX6696YAEE+  
10 μMAX  
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  
16 QSOP  
Devices are also available in tape-and-reel packages. Specify  
tape and reel by adding “T” to the part number when ordering.  
+Denotes a lead(Pb)-free/RoHS-compliant package.  
Typical Operating Circuit  
+3.3V  
0.1μF  
47Ω  
The MAX6695 has a fixed SMBus address. The  
MAX6696 has nine different pin-selectable SMBus  
addresses. The MAX6695 is available in a 10-pin  
μMAX® and the MAX6696 is available in a 16-pin QSOP  
package. Both operate throughout the -40°C to +125°C  
temperature range.  
10kΩ  
EACH  
V
CPU  
CC  
DXP1  
SMBDATA  
SMBCLK  
DATA  
CLOCK  
Applications  
Notebook Computers  
INTERRUPT  
TO μP  
ALERT  
MAX6695  
TO CLOCK  
THROTTLING  
OT1  
OT2  
DXN  
Desktop Computers  
TO SYSTEM  
SHUTDOWN  
Servers  
Workstations  
DXP2  
GND  
Test and Measurement Equipment  
GRAPHICS  
PROCESSOR  
Typical Operating Circuits continued at end of data sheet.  
Pin Configurations appear at end of data sheet.  
μMAX is a registered trademark of Maxim Integrated Products, Inc.  
________________________________________________________________ Maxim Integrated Products  
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,  
or visit Maxim’s website at www.maxim-ic.com.  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
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 μMAX (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  
Soldering Temperature (reflow) .......................................+260°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  
CC  
= +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  
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  
5/MAX96  
0.5  
35  
1
mA  
70  
Average Operating Current  
μA  
°C  
250  
500  
500  
1000  
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
T
T
T
T
T
T
T
T
T
T
= 0°C to +125°C (T = +25°C to +100°C)  
-3.0  
-5.0  
+3.0  
+5.0  
RJ  
RJ  
RJ  
A
= -40°C to +125°C (T = 0°C to +125°C)  
A
= -40°C to +125°C (T = -40°C)  
+3.0  
A
= +45°C to +85°C  
= +25°C to +100°C  
= 0°C to +125°C  
= -40°C to +125°C  
= +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
A
A
A
A
A
A
A
Local Temperature Error  
°C  
°C  
+3.0  
-3.8  
-4.0  
-4.2  
-4.4  
1.45  
500  
2.8  
Local Temperature Error  
(MAX6695Y/MAX6696Y)  
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  
2
_______________________________________________________________________________________  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
5/MAX96  
ELECTRICAL CHARACTERISTICS (continued)  
(V  
CC  
= +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  
A
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
ALERT, OT1, OT2  
Output Low Sink Current  
Output High Leakage Current  
V
V
= 0.4V  
= 3.6V  
6
1
mA  
μA  
OL  
OH  
INPUT PIN, ADD0, ADD1 (MAX6696)  
Logic Input Low Voltage  
V
0.3  
V
V
IL  
Logic Input High Voltage  
V
2.9  
IH  
INPUT PIN, RESET, STBY (MAX6696)  
Logic Input Low Voltage  
Logic Input High Voltage  
Input Leakage Current  
V
0.8  
+1  
0.8  
V
V
IL  
V
2.1  
-1  
IH  
I
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
V
V
IL  
V
2.1  
IH  
I
V
V
= GND or V  
= 0.6V  
1
6
μA  
mA  
pF  
LEAK  
IN  
CC  
I
OL  
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  
ns  
ns  
μs  
ns  
ms  
HD:STA  
SU:STO  
t
4
LOW  
t
90% to 90%  
4.7  
250  
300  
HIGH  
t
t
SU:DAT  
HD:DAT  
Data Hold Time  
SMB Rise Time  
t
1
R
SMB Fall Time  
t
F
300  
40  
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
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
Typical Operating Characteristics  
(V  
CC  
= 3.3V, T = +25°C, unless otherwise noted.)  
A
AVERAGE OPERATING SUPPLY CURRENT  
vs. CONVERSION RATE CONTROL REGISTER VALUE  
STANDBY SUPPLY CURRENT  
TEMPERATURE ERROR  
vs. REMOTE-DIODE TEMPERATURE  
vs. SUPPLY VOLTAGE  
600  
6
5
4
3
2
1
0
5
4
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
3.0  
3.1  
3.2  
3.3  
3.4  
3.5  
3.6  
-50 -25  
0
25  
50  
75 100 125  
CONVERSION RATE CONTROL REGISTER VALUE (hex)  
SUPPLY VOLTAGE (V)  
REMOTE TEMPERATURE (°C)  
5/MAX96  
TEMPERATURE ERROR  
vs. DIFFERENTIAL NOISE FREQUENCY  
TEMPERATURE ERROR  
vs. DXP-DXN CAPACITANCE  
LOCAL TEMPERATURE ERROR  
vs. DIE TEMPERATURE  
3
5
4
3
2
V
IN  
= 10mV  
P-P  
REMOTE CHANNEL2  
REMOTE CHANNEL1  
2
1
REMOTE CHANNEL2  
REMOTE CHANNEL1  
3
2
1
1
0
0
0
-1  
-2  
-3  
-4  
-5  
-1  
-1  
-2  
-3  
-2  
-3  
0.001 0.01  
0.1  
1
10  
100  
-50 -25  
0
25  
50  
75 100 125  
1
10  
100  
FREQUENCY (MHz)  
DIE TEMPERATURE (°C)  
DXP-DXN CAPACITANCE (nF)  
REMOTE TEMPERATURE ERROR  
vs. POWER-SUPPLY NOISE FREQUENCY  
LOCAL TEMPERATURE ERROR  
vs. POWER-SUPPLY NOISE FREQUENCY  
TEMPERATURE ERROR  
vs. COMMON-MODE NOISE FREQUENCY  
3
3
3
2
1
100mV  
P-P  
10mV  
P-P  
100mV  
P-P  
2
2
1
0
REMOTE CHANNEL2  
REMOTE CHANNEL1  
REMOTE CHANNEL2  
REMOTE CHANNEL1  
1
0
0
-1  
-2  
-1  
-2  
-3  
-1  
-2  
-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
_______________________________________________________________________________________  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
5/MAX96  
Pin Description  
PIN  
NAME  
FUNCTION  
MAX6695  
MAX6696  
Supply Voltage Input, +3V to +3.6V. Bypass to GND with a 0.1μF capacitor. A 47  
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 UNCONNECTED; 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  
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 UNCONNECTED; connect DXP2 to DXN if no  
remote diode is used. Place a 2200pF capacitor between DXP2 and DXN for noise  
filtering.  
5
DXP2  
Overtemperature Active-Low Output, Open Drain. OT1 is asserted low only when  
the temperature is above the programmed OT1 threshold.  
10  
OT1  
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 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  
OT2  
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
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
double that of the conversion rate for either of the other  
Detailed Description  
two channels.  
The MAX6695/MAX6696 are temperature sensors  
A BUSY status bit in status register 1 (see Table 7 and  
the Status Byte Functions section) shows that the  
device is actually performing a new conversion. The  
results of the previous conversion sequence are always  
available when the ADC is busy.  
designed to work in conjunction with a microprocessor  
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.  
Remote-Diode Selection  
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  
slower conversion rates, 3 additional bits are available  
at addresses 11h and 10h, providing +0.125°C resolu-  
tion. 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 (not the  
MAX6695Y/MAX6696Y) are optimized 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.  
5/MAX96  
ADC and Multiplexer  
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  
data obtained with the optimum ideality factor.  
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  
×
ACTUAL  
M
n
NOMINAL  
not. The DXN input is biased at one V above ground  
BE  
where temperature is measured in Kelvin and  
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 Conversion Sequence  
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,  
Remote 2. Therefore, the Remote 1 conversion rate is  
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
_______________________________________________________________________________________  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
5/MAX96  
V
(RESET)  
CC  
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
R
WRITE  
7
Q
REGISTER BANK  
COMMAND BYTE  
REMOTE TEMPERATURES  
LOCAL TEMPERATURES  
ALERT THRESHOLD  
(ADD0)  
(ADD1)  
ADDRESS  
DECODER  
OT1  
OT2  
S
R
Q
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:  
ΔV = (100μA 10μA) × R = 90μA × R  
S
M
S
°C  
Ω
3Ω × 0.453  
= +1.36°C  
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
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
In this example, the effect of the series resistance and  
Table 1. Remote-Sensor Transistor  
the ideality factor partially cancel each other.  
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  
example) indicate that the manufacturer has good  
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,  
5/MAX96  
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  
several discrete transistors from any manufacturer  
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  
ΔT = 2.2mW ×120°C / W = + 0.264°C  
Thermal Mass and Self-Heating  
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  
board is far greater than that 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 Noise Filtering  
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.  
When measuring temperature with discrete remote  
transistors, the best thermal response times are  
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  
Low-Power Standby Mode  
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
_______________________________________________________________________________________  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
5/MAX96  
Write Byte Format  
S
ADDRESS  
WR  
ACK  
COMMAND  
ACK  
DATA  
ACK  
P
7 bits  
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  
set by the command byte (to set  
thresholds, configuration masks, and  
sampling rate)  
Read Byte Format  
ADDRESS  
WR  
ACK  
COMMAND  
ACK  
S
ADDRESS  
RD  
ACK  
DATA  
///  
P
7 bits  
8 bits  
7 bits  
8 bits  
Slave Address: equiva-  
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  
Send Byte Format  
ADDRESS WR ACK COMMAND ACK  
Receive Byte Format  
P
S
ADDRESS  
RD  
ACK DATA  
8 bits  
///  
P
7 bits  
8 bits  
7 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  
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  
protocols: Write Byte, Read Byte, Send Byte, and  
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.  
SMBus Digital Interface  
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  
and alarm threshold data. The same SMBus slave  
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
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
extended temperature register (11h) (Table 3), which  
Table 2. Data Format (Two’s Complement)  
extends the temperature data to 10 bits + sign and the  
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-  
ously. 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 resolu-  
tion temperature data using 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  
5/MAX96  
FRACTIONAL  
CONTENTS OF  
TEMPERATURE (°C)  
EXTENDED REGISTER  
0
000X XXXX  
001X XXXX  
010X XXXX  
011X XXXX  
100X XXXX  
101X XXXX  
110X XXXX  
111X XXXX  
Diode Fault Alarm  
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  
Alarm Threshold Registers  
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  
and low-temperature limits, respectively. Likewise,  
WRHA and WRLN are for external channel 1 and chan-  
nel 2 high-temperature and low-temperature 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 ______________________________________________________________________________________  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
5/MAX96  
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  
Write conversion rate byte  
WCRW  
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  
11 h  
12 h  
0000 0000  
0000 0000  
Read internal extended temperature  
Read status register 2  
RSL2  
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  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
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 and OT2 Overtemperature Alarms  
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-  
tures equals or exceeds the corresponding alarm  
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 Interrupt Mode  
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.  
5/MAX96  
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.  
Alert Response Address  
The SMBus Alert Response interrupt pointer provides  
quick fault identification for simple slave devices. Upon  
receiving an interrupt signal, the host master can  
broadcast a Receive Byte transmission to the Alert  
Response slave address (see Slave Addresses sec-  
tion). Then, any slave device that generated an inter-  
rupt attempts to identify itself by putting its own  
address on the bus.  
OT1 responds immediately to temperature faults. OT2  
activates either immediately or after four consecu-  
tive remote channel temperature faults, depending on  
the state of the fault queue bit (bit 5 of the configura-  
tion register).  
Command Byte Functions  
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  
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  
One-Shot  
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 ______________________________________________________________________________________  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
5/MAX96  
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-  
shot command is received in autoconvert mode  
(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.  
Status Byte Functions  
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.  
Fault Queue Function  
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.  
Configuration Byte Functions  
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  
LOW  
HIGH  
close together, it is possible for both high-temp and  
low-temp 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.  
______________________________________________________________________________________ 13  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
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.  
5/MAX96  
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  
R2HIGH  
R2LOW  
2OPEN  
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.  
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.  
Reset (MAX6696 Only)  
Conversion Rate Byte  
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 ______________________________________________________________________________________  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
5/MAX96  
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 25ꢀ at any rate setting.  
ADD0  
ADD1  
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-  
sion, whether conversion is initiated through the  
RUN/STOP bit, hardware STBY pin, one-shot com-  
mand, or initial power-up.  
GND  
GND  
GND  
High-Z  
GND  
V
CC  
High-Z  
High-Z  
High-Z  
GND  
High-Z  
Slave Addresses  
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
V
V
GND  
CC  
CC  
CC  
High-Z  
V
CC  
Power-Up Defaults  
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  
high-impedance state detection. 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 begins autoconverting at a 4Hz rate for  
channel 2/local and 8Hz for channel 1.  
• Command register is set to 00h to facilitate quick  
internal Receive Byte queries.  
POR and UVLO  
To prevent unreliable power-supply conditions from  
corrupting the data in memory and causing erratic  
• T  
and T  
registers are set to default max  
LOW  
HIGH  
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  
below 3.0V are not recommended.  
levels  
CC  
______________________________________________________________________________________ 15  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
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  
5/MAX96  
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.  
PC Board Layout  
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 ______________________________________________________________________________________  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
5/MAX96  
Twisted-Pair and Shielded Cables  
Use a twisted-pair cable to connect the remote sensor  
GND  
for remote-sensor distances longer than 8in or in very  
10 mils  
noisy environments. Twisted-pair cable lengths can be  
between 6ft and 12ft before noise introduces excessive  
10 mils  
DXP  
errors. For longer distances, the best solution is a  
shielded twisted pair like that used for audio micro-  
phones. For example, Belden #8451 works well for dis-  
tances up to 100ft in a noisy environment. At the  
device, connect the twisted pair to DXP and DXN and  
the shield to GND. Leave the shield unconnected at the  
remote sensor.  
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.  
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 5).  
Chip Information  
PROCESS: BiCMOS  
4) Route through as few vias and crossunders as pos-  
sible to minimize copper/solder thermocouple  
effects.  
5) Use wide traces when practical.  
6) When the power supply is noisy, add a resistor (up  
to 47Ω) in series with V  
Circuit).  
(see Typical Operating  
CC  
Typical Operating Circuits (continued)  
+3.3V  
0.1μF  
47Ω  
10kΩ  
EACH  
V
CC  
CPU  
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  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
Pin Configurations  
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  
9
SMBCLK  
μMAX  
QSOP  
5/MAX96  
Package Information  
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a “+”, “#”, or  
“-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains  
to the package regardless of RoHS status.  
PACKAGE TYPE  
10 μMAX  
PACKAGE CODE  
U10CN+1  
OUTLINE NO.  
21-0061  
LAND PATTERN NO.  
90-0330  
16 QSOP  
E16+1  
21-0055  
90-0167  
18 ______________________________________________________________________________________  
Dual Remote/Local Temperature Sensors with  
SMBus Serial Interface  
5/MAX96  
Revision History  
REVISION REVISION  
PAGES  
CHANGED  
DESCRIPTION  
NUMBER  
DATE  
0
2/04  
Initial release  
Removed future status from MAX6696 in the Ordering Information table; updated the  
OT1 and OT2 Overtemperature Alarms section  
1
2
5/04  
1, 12  
Updated the Features section, Ordering Information table, Electrical Characteristics  
table, and Effect of Ideality Factor section  
11/05  
1, 2, 6  
Added lead(Pb)-free and tape-and-reel options to the Ordering Information table;  
added soldering information to the Absolute Maximum Ratings section; corrected the  
units for data setup time and data hold time from μs to ns in the Electrical  
Characteristics table; added the Package Information table  
3
4/11  
1, 2, 3, 18  
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.  
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19  
© 2011 Maxim Integrated Products  
Maxim is a registered trademark of Maxim Integrated Products, Inc.  

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