TMP401AIDGKTG4 [BB]
1C Programmable, Remote/Local, Digital Out TEMPERATURE SENSOR; 1C可编程，远程/本地，数字输出温度传感器
| 型号： | TMP401AIDGKTG4 |
| 厂家： | 
BURR-BROWN CORPORATION |
| 描述： | 1C Programmable, Remote/Local, Digital Out TEMPERATURE SENSOR |
| 文件： | 总24页 (文件大小：297K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
TMP401
SBOS371 − AUGUST 2006
+15C Programmable, Remote/Local, Digital Out
TEMPERATURE SENSOR
FD EATURES
DESCRIPTION
1°C REMOTE DIODE SENSOR
3°C LOCAL TEMPERATURE SENSOR
The TMP401 is a remote temperature sensor monitor with
built-in local temperature sensor. The remote
a
D
D
D
D
D
temperature sensor diode-connected transistors are
typically low-cost, NPN- or PNP-type transistors or diodes
that are an integral part of microcontrollers,
microprocessors, or FPGAs.
SERIES RESISTANCE CANCELLATION
THERM FLAG OUTPUT
ALERT/THERM2 FLAG OUTPUT
PROGRAMMABLE OVER/UNDER
TEMPERATURE LIMITS
Remote accuracy is 1°C for multiple IC manufacturers,
with no calibration needed. The Two-Wire serial interface
accepts SMBus write byte, read byte, send byte, and
receive byte commands to program alarm thresholds and
to read temperature data.
D
D
D
PROGRAMMABLE RESOLUTION: 9- to 12-Bit
DIODE FAULT DETECTION
SMBus SERIAL INTERFACE
Features included in the TMP401 are series resistance
cancellation, wide remote temperature measurement
range (up to +150°C), diode fault detection, and
temperature alert functions.
AD PPLICATIONS
LCD/DLPE/LCOS PROJECTORS
D
D
D
D
D
SERVERS
INDUSTRIAL CONTROLLERS
CENTRAL OFFICE TELECOM EQUIPMENT
DESKTOP AND NOTEBOOK COMPUTERS
STORAGE AREA NETWORKS
4
THERM
V+
6
ALERT/THERM2
1
TMP401
V+
5
Interrupt
Consecutive Alert
GND
Configuration
Configuration Register
Remote Temp High Limit
Remote THERM Limit
Remote Temp Low Limit
THERM Hysteresis Register
Local Temp High Limit
Local THERM Limit
One− Shot
Start Register
Status Register
Local
Temperature
Register
TL
Temperature
Comparators
Conversion Rate
Register
Local Temp Low Limit
Manufacturer ID Register
Device ID Register
D+
2
3
TR
Remote
Te m pe ra t ur e
Register
Configuration Register
Resolution Register
−
D
8
7
SCL
SDA
Pointer Register
Bus Interface
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
semiconductor products and disclaimers thereto appears at the end of this data sheet.
DLP is a trademark of Texas Instruments. All other trademarks are the property of their respective owners.
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Copyright 2006, Texas Instruments Incorporated
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SBOS371 − AUGUST 2006
This integrated circuit can be damaged by ESD. Texas
Instruments recommends that all integrated circuits be
(1)
ABSOLUTE MAXIMUM RATINGS
Power Supply, V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0V
handledwith appropriate precautions. Failure to observe
S
(2)
proper handling and installation procedures can cause damage.
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . −0.5V to V + 0.5V
S
Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10mA
Operating Temperature Range . . . . . . . . . . . . . . . −55°C to +127°C
Storage Temperature Range . . . . . . . . . . . . . . . . . −60°C to +130°C
ESD damage can range from subtle performance degradation to
complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could
cause the device not to meet its published specifications.
Junction Temperature (T max) . . . . . . . . . . . . . . . . . . . . . . +150°C
J
ESD Rating:
Human Body Model (HBM) . . . . . . . . . . . . . . . . . . . . . . . 4000V
Charged Device Model (CDM) . . . . . . . . . . . . . . . . . . . . 1000V
(1)
Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods
may degrade device reliability. These are stress ratings only, and
functional operation of the device at these or any other conditions
beyond those specified is not supported.
(2)
Input voltage rating applies to all TMP401 input voltages.
(1)
PACKAGE/ORDERING INFORMATION
PACKAGE
DESIGNATOR
PACKAGE
MARKING
PRODUCT
DESCRIPTION
ADDRESS
PACKAGE-LEAD
TMP401
Remote Junction Temperature Sensor
1001100
MSOP-8
DGK
BRB
(1)
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI website
at www.ti.com.
PIN CONFIGURATION
PIN ASSIGNMENTS
PIN
NAME
DESCRIPTION
TOP VIEW
MSOP-8
1
V+
Positive supply (3V to 5.5V)
Positive connection to remote
temperature sensor
2
3
D+
D−
TMP401
Negative connection to remote
temperature sensor
SCL
SDA
V+
D+
1
2
3
4
8
7
6
5
Thermal flag, active low, open-drain;
requires pull-up resistor to V+
4
5
THERM
GND
ALERT/THERM2
GND
−
D
Ground
Alert (reconfigurable as second
THERM
6
7
8
ALERT/THERM2 thermal flag), active low, open-drain;
requires pull-up resistor to V+
Serial data line for SMBus, open-drain;
requires pull-up resistor to V+
SDA
Serial clock line for SMBus,
SCL
open-drain; requires pull-up resistor to
V+
2
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SBOS371 − AUGUST 2006
ELECTRICAL CHARACTERISTICS: VS = 3V to 5.5V
At T = −40°C to +125°C, and V = 3V to 5.5V, unless otherwise noted.
A
S
TMP401
MIN
TYP
MAX
PARAMETER
CONDITION
UNITS
TEMPERATURE ERROR
Local Temperature Sensor
Remote Temperature Sensor
TE
T
= −40°C to +125°C
1
3
1
3
5
°C
°C
°C
°C
LOCAL
A
(1)
TE
REMOTE
T = +15°C to +75°C, T = −40°C to +150°C, V = 3.3V
A D S
T
= −40°C to +100°C, T = −40°C to +150°C, V = 3.3V
D S
A
T
A
= −40°C to +125°C, T = −40°C to +150°C, V = 3.3V
D
S
vs Supply
Local/Remote
V
S
= 3V to 5.5V
0.2
0.5
°C/V
TEMPERATURE MEASUREMENT
Conversion Time (per channel)
Resolution
One Shot Mode
115
ms
Local Temperature Sensor (programmable)
Remote Temperature Sensor
Remote Sensor Source Currents
High
9
12
Bits
Bits
12
Series Resistance 3kΩ Max
120
60
µA
µA
µA
µA
Medium High
Medium Low
12
Low
6
Remote Transistor Ideality Factor
SMBus INTERFACE
η
TMP401 Optimized Ideality Factor
1.008
Logic Input High Voltage (SCL, SDA)
Logic Input Low Voltage (SCL, SDA)
Hysteresis
V
2.1
V
V
IH
V
0.8
+1
IL
500
mV
mA
µA
pF
SMBus Output Low Sink Current
Logic Input Current
6
−1
SMBus Input Capacitance (SCL, SDA)
SMBus Clock Frequency
SMBus Timeout
3
3.4
35
1
MHz
ms
µs
30
SCL Falling Edge to SDA Valid Time
DIGITAL OUTPUTS
Output Low Voltage
V
I
I
= 6mA
= V
0.15
0.1
0.4
1
V
OL
OUT
High-Level Output Leakage Current
ALERT/THERM2 Output Low Sink Current
THERM Output Low Sink Current
POWER SUPPLY
V
µA
mA
mA
OH
OUT
S
ALERT/THERM2 Forced to 0.4V
THERM Forced to 0.4V
6
6
Specified Voltage Range
V
I
3
5.5
30
V
S
Quiescent Current
0.0625 Conversions per Second
8 Conversions per Second
25
350
3
µA
µA
µA
µA
µA
V
Q
425
10
Serial Bus Inactive, Shutdown Mode
Serial Bus Active, f = 400kHz, Shutdown Mode
S
90
Serial Bus Active, f = 3.4MHz, Shutdown Mode
S
350
1.6
Power-On Reset Threshold
TEMPERATURE RANGE
Specified Range
POR
2.5
−40
−60
+125
+130
°C
°C
Storage Range
Thermal Resistance
MSOP-8
q
JA
150
°C/W
(1)
Tested with less than 5Ω effective series resistance and 100pF differential input capacitance.
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SBOS371 − AUGUST 2006
TYPICAL CHARACTERISTICS
At T = +25°C and V = 5.0V, unless otherwise noted.
A
S
REMOTE TEMPERATURE ERROR
vs TEMPERATURE
LOCAL TEMPERATURE ERROR
vs TEMPERATURE
3
2
1
0
1
2
3
3
2
1
0
1
2
3
VS = 3.3V
TREMOTE = +25 C
28 Typical Units Shown
_
30 Typical Units Shown
η
= 1.008
−
−
−
−
−
−
−
−
25
50
0
25
50
75
100
125
−
−
25
50
0
25
50
75
100
125
_
Ambient Temperature, TA ( C)
_
Ambient Temperature, TA ( C)
Figure 1
Figure 2
REMOTE TEMPERATURE ERROR
vs LEAKAGE RESISTANCE
REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE
(Diode Connected Transistor, 2N3906 PNP)
60
40
20
0
16
14
12
10
8
VS = 3.3V
R −GND
R −VS
6
−
−
−
20
40
60
4
VS = 5.5V
2
0
−
2
0
5
10
15
20
25
30
0
500
1000
1500
2000
2500
3000
Ω
Ω
RS ( )
Leakage Resistance (M )
Figure 3
Figure 4
REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE
(GND Collector Connected Transistor, 2N3906 PNP)
REMOTE TEMPERATURE ERROR
vs DIFFERENTIAL CAPACITANCE
5
4
3
2
1
0
3
2
1
0
1
2
3
VS = 3.3V
−
−
−
VS = 5.5V
2000 2500
−
1
0
500
1000
1500
3000
0
0.5
1.0
1.5
2.0
2.5
3.0
Ω
RS ( )
Capacitance (nF)
Figure 5
Figure 6
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TYPICAL CHARACTERISTICS (continued)
At T = +25°C and V = 5.0V, unless otherwise noted.
A
S
TEMPERATURE ERROR
vs POWER−SUPPLY NOISE FREQUENCY
QUIESCENT CURRENT
vs CONVERSION RATE
25
500
450
400
350
300
250
200
150
100
50
Local 100mVPP Noise
Remote 100mVPP Noise
Local 250mVPP Noise
Remote 250mVPP Noise
20
15
10
5
0
−
5
−
10
15
20
25
−
−
−
0
0
5
10
15
0.0625 0.125 0.25
0.5
1
2
4
8
Frequency (MHz)
Conversion Rate (samples/s)
Figure 7
Figure 8
SHUTDOWN QUIESCENT CURRENT
vs SCL CLOCK FREQUENCY
SHUTDOWN QUIESCENT CURRENT
vs SUPPLY VOLTAGE
500
450
400
350
300
250
200
150
100
50
8
7
6
5
4
3
2
1
0
VS = 5.5V
VS = 3.3V
10M
0
1k
10k
100k
1M
3.0
3.5
4.0
4.5
5.0
5.5
6.0
SCL CLock Frequency (Hz)
VS (V)
Figure 9
Figure 10
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SBOS371 − AUGUST 2006
(ALERT). Additional thermal limits can be programmed
into the TMP401 and used to trigger another flag (THERM)
that can be used to initiate a system response to rising
temperatures.
APPLICATIONS INFORMATION
The TMP401 is a dual-channel digital temperature sensor
that combines a local die temperature measurement
channel and a remote junction temperature measurement
channel in a single MSOP-8 package. The TMP401 is
Two-Wire- and SMBus interface-compatible and is
specified over a temperature range of −40°C to +125°C.
The TMP401 contains multiple registers for holding
configuration information, temperature measurement
results, temperature comparator limits, and status
information.
The TMP401 requires only a transistor connected
between D+ and D− for proper remote temperature
sensing operation. The SCL and SDA interface pins
require pull-up resistors as part of the communication bus,
while ALERT and THERM are open-drain outputs that also
need pull-up resistors. ALERT and THERM may be shared
with other devices if desired for
a
wired-OR
implementation. A 0.1µF power-supply bypass capacitor
is recommended for good local bypassing. Figure 11
shows a typical configuration for the TMP401.
User-programmed high and low temperature limits stored
in the TMP401 can be used to monitor local and remote
temperatures to trigger an over/under temperature alarm
+5V
µ
0.1 F
Ω
10k
Ω
Ω
10k
Ω
10k
10k
(typ)
(typ)
(typ)
(typ)
Transistor−connected configuration(1)
:
1
Series Resistance
V+
8
(2)
SCL
SDA
RS
2
3
TMP401
D+
(3)
7
(2)
CDIFF
SMBus
Controller
RS
−
D
6
4
ALERT/THERM2
THERM
Fan Controller
GND
5
Diode−connected configuration(1)
:
(2)
RS
(3)
(1) Transistor−connected configuration provides better settling time.
NOTES:
(2)
CDIFF
RS
Diode−connected configuration provides better series resistance cancellation.
Ω
(2) RS should be < 1.5k in most applications.
(3) CDIFF should be < 1000pF in most applications.
Figure 11. Basic Connections
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SBOS371 − AUGUST 2006
temperature sensing diodes only measure with the range
of −55°C to +150°C. Additionally, the TMP401 is rated only
for ambient temperatures ranging from −40°C to +125°C.
Parameters in the Absolute Maximum Ratings table must
be observed.
SERIES RESISTANCE CANCELLATION
Series resistance in an application circuit that typically
results from printed circuit board (PCB) trace resistance
and remote line length (see Figure 11) is automatically
cancelled by the TMP401, preventing what would
otherwise result in a temperature offset. When using a 5V
supply voltage, a total of up to 3kΩ of series line resistance
is cancelled by the TMP401, eliminating the need for
additional characterization and temperature offset
correction. Series line resistance should be limited to
500Ω total when using a 3.3V supply voltage. See typical
characteristics curves (Figure 4 and Figure 5) for details
on the effect of series resistance and power-supply
voltage on sensed remote temperature error.
Table 1. Temperature Data Format
(Local and Remote Temperature High Bytes)
LOCAL/REMOTE TEMPERATURE REGISTER
HIGH BYTE VALUE (+15C RESOLUTION)
STANDARD BINARY
EXTENDED BINARY
TEMP
BINARY
0000 0000
0000 0000
0000 0000
0000 0000
0000 0001
0000 0101
0000 1010
0001 1001
0011 0010
0100 1011
0110 0100
0111 1101
0111 1111
0111 1111
0111 1111
0111 1111
HEX
BINARY
HEX
(5C)
−64
−50
−25
0
00
00
00
00
01
05
0A
19
32
4B
64
7D
7F
7F
7F
7F
0000 0000
0000 1110
0010 0111
0100 0000
0100 0001
0100 0101
0100 1010
0101 1001
0111 0010
1000 1011
1010 0100
1011 1101
1011 1111
1101 0110
1110 1111
1111 1111
00
0E
27
40
41
45
4A
59
72
8B
A4
BD
BF
D6
EF
FF
DIFFERENTIAL INPUT CAPACITANCE
1
The TMP401 tolerates differential input capacitance of up
to 1000pF with minimal change in temperature error. The
effect of capacitance on sensed remote temperature error
is shown in Figure 6, Remote Temperature Error vs
Differential Capacitance.
5
10
25
50
75
100
125
127
150
175
191
TEMPERATURE MEASUREMENT DATA
Temperature measurement data is taken over a default
range of 0°C to +127°C for both local and remote locations.
Measurements from −55°C to +150°C can be made both
locally and remotely by reconfiguring the TMP401 for the
extended temperature range. To change the TMP401
configuration from the standard to the extended
temperature range, switch bit 2 (RANGE) of the
Configuration Register from low to high.
NOTE: Whenever changing between standard and
extended temperature ranges, be aware that the
temperatures stored in the temperature limit registers are
NOT automatically reformatted to correspond to the new
temperature range format. These temperature limit values
must be reprogrammed in the appropriate binary or
extended binary format.
Temperature data resulting from conversions within the
default measurement range is represented in binary form,
as shown in Table 1, Standard Binary column. Note that
any temperature below 0°C results in a data value of zero
(00h). Likewise, temperatures above +127°C result in a
value of 127 (7Fh). The device can be set to measure over
an extended temperature range by changing bit 2 of the
Configuration Register from low to high. The change in
measurement range and data format from standard binary
to extended binary occurs at the next temperature
conversion. For data captured in the extended
temperature range configuration, an offset of 64 (40h) is
added to the standard binary value, as shown in Table 1,
Extended Binary column. This configuration allows
measurement of temperatures below 0°C. Note that binary
values corresponding to temperatures as low as −64°C,
and as high as +191°C are possible; however, most
Both local and remote temperature data use two bytes for
data storage. The high byte stores the temperature with
1°C resolution. The second or low byte stores the decimal
fraction value of the temperature and allows a higher
measurement resolution; see Table 2. The measurement
resolution for the remote channel is 0.0625°C, and is not
adjustable. The measurement resolution for the local
channel is adjustable; it can be set for 0.5°C, 0.25°C,
0.125°C, or 0.0625°C by setting the RES1 and RES0 bits
of the Resolution Register; see the Resolution Register
section.
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Table 2. Decimal Fraction Temperature Data Format (Local and Remote Temperature Low Bytes)
REMOTE
TEMPERATURE
REGISTER
LOCAL
TEMPERATURE
REGISTER
LOW BYTE VALUE
LOW BYTE VALUE
0.06255C RESOLUTION
STANDARD
AND
0.55C RESOLUTION
STANDARD
AND
0.255C RESOLUTION
STANDARD
AND
0.1255C RESOLUTION
STANDARD
AND
0.06255C RESOLUTION
STANDARD
AND
EXTENDED
BINARY
EXTENDED
BINARY
EXTENDED
BINARY
EXTENDED
BINARY
EXTENDED
BINARY
TEMP
(5C)
HEX
00
10
20
30
40
50
60
70
80
90
A0
B0
C0
D0
E0
F0
HEX
HEX
00
00
00
00
40
40
40
40
80
80
80
80
C0
C0
C0
C0
HEX
00
00
20
20
40
40
60
60
80
80
A0
A0
C0
C0
E0
E0
HEX
00
10
20
30
40
50
60
70
80
90
A0
B0
C0
D0
E0
F0
0.0000
0.0625
0.1250
0.1875
0.2500
0.3125
0.3750
0.4375
0.5000
0.5625
0.6250
0.6875
0.7500
0.8125
0.8750
0.9375
0000 0000
0001 0000
0010 0000
0011 0000
0100 0000
0101 0000
0110 0000
0111 0000
1000 0000
1001 0000
1010 0000
1011 0000
1100 0000
1101 0000
1110 0000
1111 0000
0000 0000
0000 0000
0000 0000
0000 0000
0000 0000
0000 0000
0000 0000
0000 0000
1000 0000
1000 0000
1000 0000
1000 0000
1000 0000
1000 0000
1000 0000
1000 0000
00
00
00
00
00
00
00
00
80
80
80
80
80
80
80
80
0000 0000
0000 0000
0000 0000
0000 0000
0100 0000
0100 0000
0100 0000
0100 0000
1000 0000
1000 0000
1000 0000
1000 0000
1100 0000
1100 0000
1100 0000
1100 0000
0000 0000
0000 0000
0010 0000
0010 0000
0100 0000
0100 0000
0110 0000
0110 0000
1000 0000
1000 0000
1010 0000
1010 0000
1100 0000
1100 0000
1110 0000
1110 0000
0000 0000
0001 0000
0010 0000
0011 0000
0100 0000
0101 0000
0110 0000
0111 0000
1000 0000
1001 0000
1010 0000
1011 0000
1100 0000
1101 0000
1110 0000
1111 0000
REGISTER INFORMATION
The TMP401 contains multiple registers for holding
configuration information, temperature measurement
results, temperature comparator limits, and status
information. These registers are described in Figure 12
and Table 3.
Pointer Register
Local and Remote Temperature Registers
Local and Remote Limit Registers
Hysteresis Register
SDA
SCL
Status Register
POINTER REGISTER
I/O
Control
Interface
Configuration Register
Resolution Register
Figure 12 shows the internal register structure of the
TMP401. The 8-bit Pointer Register is used to address a
given data register. The Pointer Register identifies which
of the data registers should respond to a read or write
command on the Two-Wire bus. This register is set with
every write command. A write command must be issued
to set the proper value in the Pointer Register before
executing a read command. Table 3 describes the pointer
address of the registers available in the TMP401. The
power-on reset (POR) value of the Pointer Register is 00h
(0000 0000b).
Conversion Rate Register
One−Shot Register
Consecutive Alert Register
Identification Registers
Figure 12. Internal Register Structure
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Table 3. Register Map
POINTER
ADDRESS
(HEX)
POWER-
ON
RESET
(HEX)
BIT DESCRIPTION
READ WRITE
D7
D6
D5
D4
D3
D2
D1
D0
REGISTER DESCRIPTION
Local Temperature
(High Byte)
00
01
NA
NA
00
00
LT11
LT10
LT9
LT8
LT7
LT6
LT5
LT4
Remote Temperature
(High Byte)
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
02
03
04
NA
09
XX
00
08
BUSY
MASK1
0
LHIGH
SD
LLOW
AL/TH
0
RHIGH
RLOW
0
OPEN
RANGE
R2
RTHRM
LTHRM
Status Register
0
0
0
0
Configuration Register
Conversion Rate Register
0A
0
R3
R1
R0
Local Temperature High Limit
(High Byte)
05
06
07
0B
0C
0D
55
00
55
LTH11
LTL11
RTH11
LTH10
LTL10
RTH10
LTH9
LTL9
RTH9
LTH8
LTL8
RTH8
LTH7
LTL7
RTH7
LTH6
LTL6
RTH6
LTH5
LTL5
RTH5
LTH4
LTL4
RTH4
Local Temperature Low Limit
(High Byte)
Remote Temperature High Limit
(High Byte)
Remote Temperature Low Limit
(High Byte)
08
NA
10
0E
0F
00
XX
00
RTL11
X
RTL10
X
RTL9
X
RTL8
X
RTL7
RTL6
RTL5
RTL4
X
0
X
0
X
0
X
0
One−Shot Start
Remote Temperature
(Low Byte)
NA
RT3
RT2
RT1
RT0
Remote Temperature High Limit
(Low Byte)
13
14
15
16
17
13
14
NA
16
17
00
00
00
00
00
RTH3
RTL3
LT3
RTH2
RTL2
LT2
RTH1
RTL1
LT1
RTH0
RTL0
LT0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Remote Temperature Low Limit
(Low Byte)
Local Temperature
(Low Byte)
Local Temperature High Limit
(Low Byte)
LTH3
LTL3
LTH2
LTL2
LTH1
LTL1
LTH0
LTL0
Local Temperature Low Limit
(Low Byte)
19
1A
20
21
22
FE
FF
19
1A
20
55
1C
55
0A
80
55
11
RTHL11
RTHL10
RTHL9
RTHL8
RTHL7
RTHL6
RTHL5
RES1
LTHL5
TH5
C0
RTHL4
RES0
LTHL4
TH4
0
Remote THERM Limit
Resolution Register
Local THERM Limit
THERM Hysteresis
Consecutive Alert Register
Manufacturer ID
0
LTHL11
TH11
TO_EN
0
0
0
1
1
LTHL7
TH7
C2
1
LTHL6
TH6
C1
LTHL10
LTHL9
LTHL8
21
TH10
TH9
0
TH8
0
22
0
1
0
NA
NA
0
1
0
1
0
1
0
0
1
0
0
0
1
Device ID
:
NOTE NA = Not applicable; register is write-only or read-only.
X = Indeterminate state.
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temperature low limit is read by reading the high byte from
pointer address 06h and the low byte from pointer address
17h, or by using a two-byte read from pointer address 06h.
The power-on reset value of the local temperature low limit
register is 00h/00h (0°C in standard temperature mode;
−64°C in extended mode).
TEMPERATURE REGISTERS
The TMP401 has four 8-bit registers that hold temperature
measurement results. Both the local channel and the
remote channel have a high byte register that contains the
most significant bits (MSBs) of the temperature ADC result
and a low byte register that contains the least significant
bits (LSBs) of the temperature ADC result. The local
channel high byte address is 00h; the local channel low
byte address is 15h. The remote channel high byte is at
address 01h; the remote channel low byte address is 10h.
These registers are read-only and are updated by the ADC
each time a temperature measurement is completed.
The remote temperature high limit is set by writing the high
byte to pointer address 0Dh and writing the low byte to
pointer address 13h, or by using a two-byte write
command to pointer address 0Dh. The remote
temperature high limit is obtained by reading the high byte
from pointer address 07h and the low byte from pointer
address 13h, or by using a two-byte read command from
pointer address 07h. The power-on reset value of the
remote temperature high limit register is 55h/00h (+85°C
in standard temperature mode; +21°C in extended
temperature mode).
The TMP401 contains circuitry to assure that a low byte
register read command returns data from the same ADC
conversion as the immediately preceding high byte read
command. This assurance remains valid only until another
register is read. For proper operation, the high byte of a
temperature register should be read first. The low byte
register should be read in the next read command. The low
byte register may be left unread if the LSBs are not
needed. Alternatively, the temperature registers may be
read as a 16-bit register by using a single two-byte read
command from address 00h for the local channel result or
from address 01h for the remote channel result. The high
byte will be output first, followed by the low byte. Both bytes
of this read operation will be from the same ADC
conversion. The power-on reset value of both temperature
registers is 00h.
The remote temperature low limit is set by writing the high
byte to pointer address 0Eh and writing the low byte to
pointer address 14h, or by using a two-byte write to pointer
address 0Eh. The remote temperature low limit is read by
reading the high byte from pointer address 08h and the low
byte from pointer address 14h, or by using a two-byte read
from pointer address 08h. The power-on reset value of the
remote temperature low limit register is 00h/00h (0°C in
standard temperature mode; −64°C in extended mode).
The TMP401 also has a THERM limit register for both the
local and the remote channels. These registers are eight
bits and allow for THERM limits set to 1°C resolution. The
local channel THERM limit is set by writing to pointer
address 20h. The remote channel THERM limit is set by
writing to pointer address 19h. The local channel THERM
limit is obtained by reading from pointer address 20h; the
remote channel THERM limit is read by reading from
pointer address 19h. The power-on reset value of the
THERM limit registers is 55h (+85°C in standard
temperature mode; +21°C in extended temperature
mode). The THERM limit comparators also have
hysteresis. The hysteresis of both comparators is set by
writing to pointer address 21h. The hysteresis value is
obtained by reading from pointer address 21h. The value
in the hysteresis register is an unsigned number (always
positive). The power-on reset value of this register is 0Ah
(+10°C).
LIMIT REGISTERS
The TMP401 has 11 registers for setting comparator limits
for both the local and remote measurement channels.
These registers have read and write capability. The high
and low limit registers for both channels span two
registers, as do the temperature registers. The local
temperature high limit is set by writing the high byte to
pointer address 0Bh and writing the low byte to pointer
address 16h, or by using a single two-byte write command
(high byte first) to pointer address 0Bh. The local
temperature high limit is obtained by reading the high byte
from pointer address 05h and the low byte from pointer
address 16h, or by using a two-byte read command from
pointer address 05h. The power-on reset value of the local
temperature high limit is 55h/00h (+85°C in standard
temperature mode; +21°C in extended temperature
mode).
Whenever changing between standard and extended
temperature ranges, be aware that the temperatures
stored in the temperature limit registers are NOT
automatically reformatted to correspond to the new
temperature range format. These values must be
reprogrammed in the appropriate binary or extended
binary format.
Similarly, the local temperature low limit is set by writing
the high byte to pointer address 0Ch and writing the low
byte to pointer address 17h, or by using a single two-byte
write command to pointer address 0Ch. The local
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The RHIGH bit reads as ‘1’ if the remote temperature has
exceeded the remote high limit and remains greater than
the remote high limit less the value in the Hysteresis
Register.
STATUS REGISTER
The TMP401 has a status register to report the state of the
temperature comparators. Table 4 shows the Status
Register bits. The Status Register is read-only and is read
by reading from pointer address 02h.
The LLOW and RLOW bits are not affected by the AL/TH
bit. The LLOW bit reads as ‘1’ if the local low limit was
exceeded since the last clearing of the Status Register.
The RLOW bit reads as ‘1’ if the remote low limit was
exceeded since the last clearing of the Status Register.
The BUSY bit reads as ‘1’ if the ADC is making a
conversion. It reads as ‘0’ if the ADC is not converting.
The OPEN bit reads as ‘1’ if the remote transistor was
detected as open since the last read of the Status Register.
The OPEN status is only detected when the ADC is
attempting to convert a remote temperature.
The values of the LLOW, RLOW, and OPEN (as well as
LHIGH and RHIGH when AL/TH is ‘0’) are latched and will
read as ‘1’ until the Status Register is read or a device reset
occurs. These bits are cleared by reading the Status
Register, provided that the condition causing the flag to be
set no longer exists. The values of BUSY, LTHRM, and
RTHRM (as well as LHIGH and RHIGH when AL/TH is ‘1’)
are not latched and are not cleared by reading the Status
Register. They always indicate the current state, and are
updated appropriately at the end of the corresponding
ADC conversion. Clearing the Status Register bits does
not clear the state of the ALERT pin; an SMBus alert
response address command must be used to clear the
ALERT pin.
The RTHRM bit reads as ‘1’ if the remote temperature has
exceeded the remote THERM limit and remains greater
than the remote THERM limit less the value in the shared
hysteresis register; see Figure 17.
The LTHRM bit reads as ‘1’ if the local temperature has
exceeded the local THERM limit and remains greater than
the local THERM limit less the value in the shared
hysteresis register; see Figure 17.
The LHIGH and RHIGH bit values depend on the state of
the AL/TH bit in the Configuration Register. If the AL/TH bit
is ‘0’, the LHIGH bit reads as ‘1’ if the local high limit was
exceeded since the last clearing of the Status Register.
The RHIGH bit reads as ‘1’ if the remote high limit was
exceeded since the last clearing of the Status Register. If
the AL/TH bit is ‘1’, the remote high limit and the local high
limit are used to implement a THERM2 function. LHIGH
reads as ‘1’ if the local temperature has exceeded the local
high limit and remains greater than the local high limit less
the value in the Hysteresis Register.
The TMP401 NORs LHIGH, LLOW, RHIGH, RLOW, and
OPEN, so a status change for any of these flags from ‘0’
to ‘1’ automatically causes the ALERT pin to go low (only
applies when the ALERT/THERM2 pin is configured for
ALERT mode).
Table 4. Status Register Format
STATUS REGISTER (Read = 02h, Write = NA)
BIT #
BIT NAME
D7
D6
LHIGH
0
D5
LLOW
0
D4
RHIGH
0
D3
RLOW
0
D2
OPEN
0
D1
RTHRM
0
D0
LTHRM
0
BUSY
(1)
0
POR VALUE
(1)
The BUSY bit will change to ‘1’ almost immediately (<< 100µs) following power-up, as the TMP401 begins the first temperature conversion.
It will be high whenever the TMP401 is converting a temperature reading.
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The AL/TH bit (bit 5) controls whether the ALERT pin
functions in ALERT mode or THERM2 mode. If AL/TH = 0,
the ALERT pin operates as an interrupt pin. In this mode, the
ALERT pin goes low after the set number of consecutive
out-of-limit temperature measurements occur.
CONFIGURATION REGISTER
The Configuration Register sets the temperature range,
controls Shutdown mode, and determines how the
ALERT/THERM2 pin functions. The Configuration
Register is set by writing to pointer address 09h and read
by reading from pointer address 03h.
If AL/TH = 1, the ALERT/THERM2 pin implements a
THERM function (THERM2). In this mode, THERM2
functions similar to the THERM pin except that the local
high limit and remote high limit registers are used for the
thresholds. THERM2 goes low when either RHIGH or
LHIGH is set.
The MASK bit (bit 7) enables or disables the ALERT pin
output if AL/TH = 0. If AL/TH = 1 then the MASK bit has no
effect. If MASK is set to ‘0’, the ALERT pin goes low when
one of the temperature measurement channels exceeds
its high or low limits for the chosen number of consecutive
conversions. If the MASK bit is set to ‘1’, the TMP401
retains the ALERT pin status, but the ALERT pin will not
go low.
The temperature range is set by configuring bit 2 of the
Configuration Register. Setting this bit low configures the
TMP401 for the standard measurement range (0°C to
+127°C); temperature conversions will be stored in the
standard binary format. Setting bit 2 high configures the
TMP401 for the extended measurement range (−55°C to
+150°C); temperature conversions will be stored in the
extended binary format (see Table 1).
The shutdown (SD) bit (bit 6) enables or disables the
temperature measurement circuitry. If SD = 0, the TMP401
converts continuously at the rate set in the Conversion
Rate Register. When SD is set to ‘1’, the TMP401
immediately stops converting and enters a shutdown
mode. When SD is set to ‘0’ again, the TMP401 resumes
continuous conversions. A single conversion can be
started when SD = 1 by writing to the One-Shot Register.
The remaining bits of the Configuration Register are
reserved and must always be set to ‘0’. The power-on reset
value for this register is 00h. Table 5 summarizes the bits
of the Configuration Register.
Table 5. Configuration Register Bit Descriptions
CONFIGURATION REGISTER (Read = 02h, Write = NA)
BIT
NAME
FUNCTION
POWER-ON RESET VALUE
0 = ALERT Enabled
1 = ALERT Masked
7
MASK
SD
0
0 = Run
1 = Shut Down
6
0
0 = ALERT Mode
1 = THERM Mode
5
AL/TH
Reserved
0
0
0
0
4, 3
2
—
0 = 0°C to +127°C
1 = −55°C to +150°C
Temperature Range
Reserved
1, 0
—
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RESOLUTION REGISTER
CONVERSION RATE REGISTER
The RES1 and RES0 bits (resolution bits 1 and 0) of the
Resolution Register set the resolution of the local
temperature measurement channel. Remote temperature
measurement channel resolution is not affected.
Changing the local channel resolution also affects the
conversion time and rate of the TMP401. The resolution
register is set by writing to pointer address 1Ah and is read
by reading from pointer address 1Ah. Table 6 shows the
resolution bits for the Resolution Register.
The Conversion Rate Register controls the rate at which
temperature conversions are performed. This register
adjusts the idle time between conversions but not the
conversion timing itself, thereby allowing the TMP401
power dissipation to be balanced with the temperature
register update rate. Table 7 shows the conversion rate
options and corresponding current consumption.
ONE-SHOT CONVERSION
Table 6. Resolution Register:
When the TMP401 is in shutdown mode (SD = 1 in the
Configuration Register), a single conversion on both
channels is started by writing any value to the One-Shot
Start Register, pointer address 0Fh. This write operation
starts one conversion; the TMP401 returns to shutdown
mode when that conversion completes. The value of the
data sent in the write command is irrelevant and is not
stored by the TMP401. When the TMP401 has been set to
shutdown mode, an initial 200µs is required before a
one-shot command can be given. This wait time only
applies to the 200µs immediately following shutdown.
One-shot commands can be issued without delay
thereafter.
Local Channel Programmable Resolution
RESOLUTION REGISTER (Read = 1Ah, Write = 1Ah, POR = 1Ch)
CONVERSION TIME
(Typical)
12.5ms
25ms
RES1
RES0
RESOLUTION
9 Bits (0.5°C)
0
0
1
1
0
1
0
1
10 Bits (0.25°C)
11 Bits (0.125°C)
12 Bits (0.0625°C)
50ms
100ms
Bits 2 through 4 of the Resolution Register must always be
set to ‘1’. Bits 5 through 7 of the Resolution Register must
always be set to ‘0’. The power-on reset value of this
register is 1Ch.
Table 7. Conversion Rate Register
CONVERSION RATE REGISTER
AVERAGE I (typ)
Q
(µA)
V
S
= 3V
V
S
= 5V
29
R7
R6
R5
R4
R3
R2
R1
R0
CONVERSION/SEC
0
0
0
0
0
0
0
0
0.0625
8
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
0
1
1
0
0
1
1
0
1
0
1
0
0.125
11
15
24
41
69
31
0.25
0.5
1
36
45
63
2
92
4
111
136
355
07h to 0Fh
8
320
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Local Temperature High Limit Register value, Remote
Temperature High Limit Register value, Local THERM
Limit Register value, or Remote THERM Limit Register
value; otherwise, the respective temperature comparator
will not trip on the measured temperature falling edges.
Allowable hysteresis values are shown in Table 9. The
default hysteresis value is 10°C, whether the device is
operating in the standard or extended mode setting.
CONSECUTIVE ALERT REGISTER
The value in the Consecutive Alert Register (address 22h)
determines how many consecutive out-of-limit
measurements must occur on a measurement channel
before the ALERT signal is activated. The value in this
register does not affect bits in the Status Register. Values
of one, two, three, or four consecutive conversions can be
selected; one conversion is the default. This function
allows additional filtering for the ALERT pin. The
consecutive alert bits are shown in Table 8.
Table 9. Allowable THERM Hysteresis Values
THERM HYSTERESIS VALUE
TH[11:4]
(STANDARD BINARY)
TEMPERATURE
Table 8. Consecutive Alert Register
(HEX)
00
(5C)
0
CONSECUTIVE ALERT REGISTER
0000 0000
0000 0001
0000 0101
0000 1010
0001 1001
0011 0010
0100 1011
0110 0100
0111 1101
0111 1111
1001 0110
1010 1111
1100 1000
1110 0001
1111 1111
NUMBER OF CONSECUTIVE
OUT-OF-LIMIT MEASUREMENTS
1
01
C2
0
C1
0
C0
0
5
05
1
2
3
4
10
0A
19
0
0
1
25
0
1
1
50
32
1
1
1
75
4B
64
100
125
127
150
175
200
225
255
7D
7F
96
NOTE: Bit 7 of the Consecutive Alert Register controls the
enable/disable of the timeout function. See the Timeout
Function section for a description of this feature.
AF
C8
E1
FF
THERM HYSTERESIS REGISTER
The THERM Hysteresis Register stores the hysteresis
value used for the THERM pin alarm function. This register
must be programmed with a value that is less than the
Table 10. THERM Hysteresis Register Format
THERM HYSTERESIS REGISTER (Read = 21h, Write = 21h)
BIT #
BIT NAME
D7
TH11
0
D6
TH10
0
D5
TH9
0
D4
TH8
0
D3
TH7
1
D2
TH6
0
D1
TH5
1
D0
TH4
0
POR VALUE
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first byte transferred after the slave address byte with the
R/W bit low. Every write operation to the TMP401 requires
a value for the Pointer Register (see Figure 14).
BUS OVERVIEW
The TMP401 is SMBus interface-compatible. In SMBus
protocol, the device that initiates the transfer is called a
master, and the devices controlled by the master are
slaves. The bus must be controlled by a master device that
generates the serial clock (SCL), controls the bus access,
and generates the START and STOP conditions.
When reading from the TMP401, the last value stored in
the Pointer Register by a write operation is used to
determine which register is read by a read operation. To
change the register pointer for a read operation, a new
value must be written to the pointer register. This
transaction is accomplished by issuing a slave address
byte with the R/W bit low, followed by the pointer register
byte. No additional data is required. The master can then
generate a START condition and send the slave address
byte with the R/W bit high to initiate the read command.
See Figure 15 for details of this sequence. If repeated
reads from the same register are desired, it is not
necessary to continually send the pointer register bytes,
because the TMP401 retains the Pointer Register value
until it is changed by the next write operation. Note that
register bytes are sent MSB first, followed by the LSB.
To address a specific device, a START condition is
initiated. START is indicated by pulling the data line (SDA)
from a high to low logic level while SCL is high. All slaves
on the bus shift in the slave address byte, with the last bit
indicating whether a read or write operation is intended.
During the ninth clock pulse, the slave being addressed
responds to the master by generating an Acknowledge
and pulling SDA low.
Data transfer is then initiated and sent over eight clock
pulses followed by an Acknowledge bit. During data
transfer SDA must remain stable while SCL is high,
because any change in SDA while SCL is high is
interpreted as a control signal.
TIMING DIAGRAMS
Once all data has been transferred, the master generates
a STOP condition. STOP is indicated by pulling SDA from
low to high, while SCL is high.
The TMP401 is Two-Wire and SMBus compatible.
Figure 13 to Figure 16 describe the various operations on
the TMP401. Bus definitions are given below. Parameters
for Figure 13 are defined in Table 11.
SERIAL INTERFACE
Bus Idle: Both SDA and SCL lines remain high.
The TMP401 operates only as a slave device on either the
Two-Wire bus or the SMBus. Connections to either bus are
made via the open-drain I/O lines, SDA and SCL. The SDA
and SCL pins feature integrated spike suppression filters
and Schmitt triggers to minimize the effects of input spikes
and bus noise. The TMP401 supports the transmission
protocol for fast (1kHz to 400kHz) and high-speed (1kHz
to 3.4MHz) modes. All data bytes are transmitted MSB
first.
Start Data Transfer: A change in the state of the SDA line,
from high to low, while the SCL line is high, defines a
START condition. Each data transfer is initiated with a
START condition.
Stop Data Transfer: A change in the state of the SDA line
from low to high while the SCL line is high defines a STOP
condition. Each data transfer terminates with a repeated
START or STOP condition.
Data Transfer: The number of data bytes transferred
between a START and a STOP condition is not limited and
is determined by the master device. The receiver
acknowledges the transfer of data.
SERIAL BUS ADDRESS
To communicate with the TMP401, the master must first
address slave devices via a slave address byte. The slave
address byte consists of seven address bits, and a
direction bit indicating the intent of executing a read or
write operation. The address of the TMP401 is 4Ch
(1001100b).
Acknowledge: Each receiving device, when addressed,
is obliged to generate an Acknowledge bit. A device that
acknowledges must pull down the SDA line during the
Acknowledge clock pulse in such a way that the SDA line
is stable low during the high period of the Acknowledge
clock pulse. Setup and hold times must be taken into
account. On a master receive, data transfer termination
READ/WRITE OPERATIONS
can be signaled by the master generating
a
Not-Acknowledge on the last byte that has been
transmitted by the slave.
Accessing a particular register on the TMP401 is
accomplished by writing the appropriate value to the
Pointer Register. The value for the Pointer Register is the
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t(LOW)
tF
tR
t(HDSTA)
SCL
t(SUSTO)
t(HDSTA)
t(HIGH) t(SUSTA)
t(HDDAT)
t(SUDAT)
SDA
t(BUF)
P
S
S
P
Figure 13. Two-Wire Timing Diagram
Table 11. Timing Diagram Definitions for Figure 13
PARAMETER
MIN
0.001
600
MAX
MIN
0.001
160
MAX
UNITS
MHz
ns
SCL Operating Frequency
f
t
0.4
3.4
(SCL)
Bus Free Time Between STOP and START Condition
(BUF)
Hold time after repeated START condition.
After this period, the first clock is generated.
t
100
100
ns
(HDSTA)
Repeated START Condition Setup Time
STOP Condition Setup Time
Data Hold Time
t
100
100
0
100
100
0
ns
ns
ns
ns
ns
ns
ns
(SUSTA)
t
(SUSTO)
t
(HDDAT)
Data Setup Time
t
100
1300
600
10
(SUDAT)
SCL Clock LOW Period
SCL Clock HIGH Period
Clock/Data Fall Time
t
160
60
(LOW)
t
(HIGH)
t
F
300
160
160
Clock/Data Rise Time
t
R
t
R
300
1000
ns
for SCL ≤ 100kHz
1
9
1
9
…
…
SCL
SDA
1
1
0
0
1
1
0
0
R/W
P7 P6 P5 P4 P3
P2 P1
P0
Start By
Master
ACK By
TMP401
ACK By
TMP401
Frame 2 Pointer Register Byte
Frame 1 Two−Wire Slave Address Byte
9
1
9
SCL
(Continued)
SDA
(Continued)
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
ACK By
TMP401
ACK By
TMP401
Stop By
Master
Frame 3 Data Byte 1
Frame 4 Data Byte 2
Figure 14. Two-Wire Timing Diagram for Write Word Format
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1
9
1
9
…
SCL
SDA
…
1
0
0
1
R/W
P7
P6
P5
P4
P3
P2
P1
P0
1
0
0
Start By
Master
ACK By
TMP401
ACK By
TMP401
Frame 1 Two−Wire Slave Address Byte
Frame 2 Pointer Register Byte
1
9
1
9
SCL
(Continued)
…
SDA
(Continued)
…
0
0
0
1
0
0
1
R/W
D7
D6
D5
D4 D3
D2
D1
D0
Start By
Master
ACK By
TMP401
From
TMP401
ACK By
Master
Frame 3 Two−Wire Slave Address Byte
9
Frame 4 Data Byte 1 Read Register
1
SCL
(Continued)
SDA
(Continued)
D7 D6
D5
D4
D3
D2
D1
D0
From
TMP401
ACK By
Master
Stop By
Master
Frame 5 Data Byte 2 Read Register
Figure 15. Two-Wire Timing Diagram for Read Word Format
ALERT
SCL
1
0
9
1
9
Status
SDA
0
0
1
1
0
0
R/W
1
0
0
1
1
0
0
Start By
Master
ACK By
TMP401
From
TMP401
NACK By Stop By
Master Master
Frame 1 SMBus ALERT Response Address Byte
Frame 2 Slave Address Byte
Figure 16. Timing Diagram for SMBus ALERT
17
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or masked. The ALERT/THERM2 pin can also be
configured for use as THERM2, a second THERM pin
(Configuration Register: AL/TH bit = 1). The default setting
configures pin 6 to function as ALERT (AL/TH = 0).
HIGH-SPEED MODE
In order for the Two-Wire bus to operate at frequencies
above 400kHz, the master device must issue a
High-speed mode (Hs-mode) master code (00001XXX) as
the first byte after a START condition to switch the bus to
high-speed operation. The TMP401 will not acknowledge
this byte, but will switch the input filters on SDA and SCL
and the output filter on SDA to operate in Hs-mode,
allowing transfers at up to 3.4MHz. After the Hs-mode
master code has been issued, the master will transmit a
Two-Wire slave address to initiate a data transfer
operation. The bus will continue to operate in Hs-mode
until a STOP condition occurs on the bus. Upon receiving
the STOP condition, the TMP401 switches the input and
output filter back to fast-mode operation.
The THERM pin asserts low when either the measured
local or remote temperature is outside of the temperature
range programmed in the corresponding Local/Remote
THERM Limit Register. The THERM temperature limit
range can be programmed with a wider range than that of
the limit registers, which allows ALERT to provide an
earlier warning than THERM. The THERM alarm resets
automatically when the measured temperature returns to
within the THERM temperature limit range minus the
hysteresis value stored in the THERM Hysteresis
Register. The allowable values of hysteresis are shown in
Table 9. The default hysteresis is 10°C. When the
ALERT/THERM2 pin is configured as a second thermal
alarm (Configuration Register: bit 7 = 0, bit 5 = 1), it
functions the same as THERM, but uses the temperatures
stored in the Local/Remote Temperature High/Low Limit
Registers to set its comparison range.
TIMEOUT FUNCTION
When bit 7 of the Consecutive Alert Register is set high,
the TMP401 timeout function is enabled. The TMP401
resets the serial interface if either SCL or SDA are held low
for 30ms (typ) between a START and STOP condition. If
the TMP401 is holding the bus low, it releases the bus and
waits for a START condition. To avoid activating the
When ALERT/THERM2 (pin 6) is configured as ALERT
(Configuration Register: bit 7 = 0, bit 5 = 0), the pin asserts
low when either the measured local or remote temperature
violates the range limit set by the corresponding
Local/Remote Temperature High/Low Limit Registers.
This alert function can be configured to assert only if the
range is violated a specified number of consecutive times
(1, 2, 3, or 4). The consecutive violation limit is set in the
Consecutive Alert Register. False alerts that occur as a
result of environmental noise can be prevented by
requiring consecutive faults. ALERT also asserts low if the
remote temperature sensor is open-circuit. When the
MASK function is enabled (Configuration Register: bit 7 = 1),
ALERT is disabled (that is, masked). ALERT resets when
the master reads the device address, as long as the
condition that caused the alert no longer persists, and the
Status Register has been reset.
timeout function, it is necessary to maintain
a
communication speed of at least 1kHz for the SCL
operating frequency. The default state of the timeout
function is enabled (bit 7 = high).
THERM (PIN 4) AND ALERT/THERM2 (PIN 6)
The TMP401 has two pins dedicated to alarm functions,
the THERM and ALERT/THERM2 pins. Both pins are
open-drain outputs that each require a pull-up resistor to
V+. These pins can be wire-ORed together with other
alarm pins for system monitoring of multiple sensors. The
THERM pin provides a thermal interrupt that cannot be
software disabled. The ALERT pin is intended for use as
an earlier warning interrupt, and can be software disabled,
THERM Limit and ALERT High Limit
Measured
Temperature
ALERT Low Limit and THERM Limit Hysteresis
THERM
ALERT
SMBus ALERT
Read
Read
Time
Read
Figure 17. SMBus Alert Timing Diagram
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SBOS371 − AUGUST 2006
temperature is used for the temperature measurement
result, the OPEN bit (Status Register, bit 2) is set high, and,
if the alert function is enabled, ALERT asserts low.
SMBus ALERT FUNCTION
The TMP401 supports the SMBus Alert function. When pin
6 is configured as an alert output, the ALERT pin of the
TMP401 may be connected as an SMBus Alert signal.
When a master detects an alert condition on the ALERT
line, the master sends an SMBus Alert command
(00011001) on the bus. If the ALERT pin of the TMP401 is
active, the devices will acknowledge the SMBus Alert
command and respond by returning its slave address on
the SDA line. The eighth bit (LSB) of the slave address
byte indicates whether the temperature exceeding one of
the temperature high limit settings or falling below one of
the temperature low limit settings caused the alert
condition. This bit will be high if the temperature is greater
than or equal to one of the temperature high limit settings;
this bit will be low if the temperature is less than one of the
temperature low limit settings. See Figure 16 for details of
this sequence.
When not using the remote sensor with the TMP401, the
D+ and D− inputs must be connected together to prevent
meaningless fault warnings.
GENERAL CALL RESET
The TMP401 supports reset via the Two-Wire General Call
address 00h (0000 0000b). The TMP401 acknowledges
the General Call address and responds to the second byte.
If the second byte is 06h (0000 0110b), the TMP401
executes a software reset. This software reset restores the
power-on reset state to all TMP401 registers, aborts any
conversion in progress, and clears the ALERT and
THERM pins. The TMP401 takes no action in response to
other values in the second byte.
If multiple devices on the bus respond to the SMBus Alert
command, arbitration during the slave address portion of
the SMBus Alert command determines which device will
clear its alert status. If the TMP401 wins the arbitration, its
ALERT pin becomes inactive at the completion of the
SMBus Alert command. If the TMP401 loses the
arbitration, the ALERT pin remains active.
IDENTIFICATION REGISTERS
The TMP401 allows for the Two-Wire bus controller to
query the device for manufacturer and device IDs to allow
for software identification of the device at the particular
Two-Wire bus address. The manufacturer ID is obtained
by reading from pointer address FEh. The device ID is
obtained by reading from pointer address FFh. The
TMP401 returns 55h for the manufacturer code and 11h for
the device ID. These registers are read-only.
SHUTDOWN MODE (SD)
The TMP401 Shutdown Mode allows the user to save
maximum power by shutting down all device circuitry other
than the serial interface, reducing current consumption to
typically less than 3µA; see Figure 10, Shutdown
Quiescent Current vs Supply Voltage. Shutdown Mode is
enabled when the SD bit of the Configuration Register is
high; the device shuts down once the current conversion
is completed. When SD is low, the device maintains a
continuous conversion state.
FILTERING
Remote junction temperature sensors are usually
implemented in a noisy environment. Noise is most often
created by fast digital signals, and it can corrupt
measurements. The TMP401 has a built-in 65kHz filter on
the inputs of D+ and D− to minimize the effects of noise.
However, a bypass capacitor placed differentially across
the inputs of the remote temperature sensor is
recommended to make the application more robust
against unwanted coupled signals. The value of the
capacitor should be between 100pF and 1nF. Some
applications attain better overall accuracy with additional
series resistance; however, this is setup-specific. When
series resistance is added, the value should not be greater
than 100Ω.
SENSOR FAULT
The TMP401 will sense a fault at the D+ input resulting
from incorrect diode connection or an open circuit. The
detection circuitry consists of a voltage comparator that
trips when the voltage at D+ exceeds (V+) − 0.6V (typical).
The comparator output is continuously checked during a
conversion. If a fault is detected, the last valid measured
19
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2. Base-emitter voltage < 0.95V at 120µA, at the
REMOTE SENSING
lowest sensed temperature.
The TMP401 is designed to be used with either discrete
transistors or substrate transistors built into processor
chips and ASICs. Either NPN or PNP transistors can be
used, as long as the base-emitter junction is used as the
remote temperature sense. Either a transistor or diode
connection can also be used (see Figure 11, Basic
Connections).
3. Base resistance < 100Ω.
4. Tight control of V
characteristics indicated by
BE
small variations in h (that is, 50 to 150).
FE
Based on these criteria, two recommended small-signal
transistors are the 2N3904 (NPN) or 2N3906 (PNP).
Errors in remote temperature sensor readings will be the
consequence of the ideality factor and current excitation
used by the TMP401 versus the manufacturer’s specified
MEASUREMENT ACCURACY AND THERMAL
CONSIDERATIONS
operating current for
a
given transistor. Some
manufacturers specify a high-level and low-level current
for the temperature-sensing substrate transistors. The
The temperature measurement accuracy of the TMP401
depends on the remote and/or local temperature sensor
being at the same temperature as the system point being
monitored. Clearly, if the temperature sensor is not in good
thermal contact with the part of the system being
monitored, then there will be a delay in the response of the
sensor to a temperature change in the system. For remote
temperature sensing applications using a substrate
transistor (or a small, SOT23 transistor) placed close to the
device being monitored, this delay is usually not a concern.
TMP401 uses 6µA for I
and 120µA for I
.
LOW
HIGH
The ideality factor (η) is a measured characteristic of a
remote temperature sensor diode as compared to an ideal
diode. The ideality factor for the TMP401 is trimmed to be
1.008. For transistors whose ideality factor does not match
the TMP401, Equation (1) can be used to calculate the
temperature error. Note that for the equation to be used
correctly, actual temperature (°C) must be converted to
Kelvin (°K).
The local temperature sensor inside the TMP401 monitors
the ambient air around the device. The thermal time
constant for the TMP401 is approximately two seconds.
This constant implies that if the ambient air changes
quickly by 100°C, it would take the TMP401 about 10
seconds (that is, five thermal time constants) to settle to
within 1°C of the final value. In most applications, the
TMP401 package is in electrical and therefore thermal
contact with the PCB, as well as subjected to forced
airflow. The accuracy of the measured temperature
directly depends on how accurately the PCB and forced
airflow temperatures represent the temperature that the
TMP401 is measuring. Additionally, the internal power
dissipation of the TMP401 can cause the temperature to
rise above the ambient or PCB temperature. The internal
power dissipated as a result of exciting the remote
temperature sensor is negligible because of the small
currents used. For a 5.5V supply and maximum
conversion rate of eight conversions per second, the
ǒ
Ǔ
h * 1.008
1.008
ƪ
ƫ
+ ƪ ƫ
TERR
273.15 ) T(°C)
(1)
Where:
η = Ideality factor of remote temperature sensor.
T(°C) = actual temperature.
T
= Error in TMP401 reading due to η ≠ 1.008.
Degree delta is the same for °C and °K.
ERR
For η = 1.004 and T(°C) = 100°C:
(
)
1.004*1.008
ƪ
ƫ
+ ƪ
ƫ
TERR
273.15)100°C
1.008
TERR + * 1.48°C
(2)
TMP401 dissipates 1.82mW (PD = 5.5V x 330µA). If both
IQ
If a discrete transistor is used as the remote temperature
sensor with the TMP401, the best accuracy can be
achieved by selecting the transistor according to the
following criteria:
the ALERT/THERM2 and THERM pins are each sinking
1mA, an additional power of 0.8mW is dissipated
(PD
= 1mA × 0.4V + 1mA × 0.4V = 0.8mW). Total power
OUT
dissipation is then 2.62mW (PD + PD
) and, with an
IQ
OUT
q
of 150°C/W, causes the junction temperature to rise
JA
1. Base-emitter voltage > 0.25V at 6µA, at the highest
approximately 0.393°C above the ambient.
sensed temperature.
20
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LAYOUT CONSIDERATIONS
Remote temperature sensing on the TMP401 measures
very small voltages using very small currents; therefore,
noise at the IC inputs must be minimized. Most
applications using the TMP401 will have high digital
content, with several clocks and logic level transitions
creating a noisy environment. Layout should adhere to the
following guidelines:
GND(1)
D+(1)
Ground or V+ layer
on bottom and/or
top, if possible.
1. Place the TMP401 as close to the remote junction
sensor as possible.
(1)
−
D
2. Route the D+ and D− traces next to each other and
shield them from adjacent signals through the use
of ground guard traces, as shown in Figure 18. If a
multilayer PCB is used, bury these traces between
GND(1)
ground or V planes to shield them from extrinsic
DD
noise sources. 5 mil PCB traces are recommended.
NOTE: (1) 5 mil traces with 5 mil spacing.
3. Minimize additional thermocouple junctions caused
by copper-to-solder connections. If these junctions
are used, make the same number and approximate
locations of copper-to-solder connections in both
the D+ and D− connections to cancel any
thermocouple effects.
Figure 18. Example Signal Traces
4. Use a 0.1µF local bypass capacitor directly
between the V+ and GND of the TMP401, as shown
in Figure 19. Minimize filter capacitance between
D+ and D− to 1000pF or less for optimum
measurement performance. This capacitance
includes any cable capacitance between the
remote temperature sensor and TMP401.
µ
0.1 F Capacitor
V+
GND
PCB Via
PCB Via
1
8
7
6
5
2
3
4
5. If the connection between the remote temperature
sensor and the TMP401 is between 8 inches and 12
feet, use a twisted-wire pair connection. Beyond
this distance (up to 100ft), use a twisted, shielded
pair with the shield grounded as close to the
TMP401 as possible. Leave the remote sensor
connection end of the shield wire open to avoid
ground loops and 60Hz pickup.
TMP401
Figure 19. Suggested Bypass Capacitor
Placement
21
PACKAGE OPTION ADDENDUM
www.ti.com
12-Sep-2006
PACKAGING INFORMATION
Orderable Device
TMP401AIDGKR
TMP401AIDGKRG4
TMP401AIDGKT
Status (1)
ACTIVE
ACTIVE
ACTIVE
ACTIVE
Package Package
Pins Package Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
Qty
Type
Drawing
MSOP
DGK
8
8
8
8
2500 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
MSOP
MSOP
MSOP
DGK
DGK
DGK
2500 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
TMP401AIDGKTG4
250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to discontinue
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TI warrants performance of its hardware products to the specifications applicable at the time of sale in
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TI assumes no liability for applications assistance or customer product design. Customers are responsible for
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