TMP400
TM
P4
00
SBOS404 – DECEMBER 2007
±1°C Remote and Local TEMPERATURE SENSOR
with N-Factor and Series Resistance Correction
FEATURES
1
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234
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±1°C REMOTE DIODE SENSOR
±1°C LOCAL TEMPERATURE SENSOR
PROGRAMMABLE NON-IDEALITY FACTOR
PROGRAMMABLE SERIES RESISTANCE
CANCELLATION
ALERT FUNCTION
PROGRAMMABLE RESOLUTION: 9 to 12 Bits
PROGRAMMABLE THRESHOLD LIMITS
TWO-WIRE/SMBus™ SERIAL INTERFACE
MINIMUM AND MAXIMUM TEMPERATURE
MONITORS
MULTIPLE INTERFACE ADDRESSES
ALERT PIN CONFIGURATION
DIODE FAULT DETECTION
APPLICATIONS
•
•
•
•
•
•
•
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LCD/DLP®/LCOS PROJECTORS
SERVERS
INDUSTRIAL CONTROLLERS
CENTRAL OFFICE TELECOM EQUIPMENT
DESKTOP AND NOTEBOOK COMPUTERS
STORAGE AREA NETWORKS (SAN)
INDUSTRIAL AND MEDICAL EQUIPMENT
PROCESSOR/FPGA TEMPERATURE
MONITORING
DESCRIPTION
The TMP400 is a remote temperature sensor monitor
with a built-in local temperature sensor. The remote
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.
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 the alarm thresholds and to read
temperature data.
The TMP400 is customizable with programmable:
series resistance cancellation, non-ideality factor,
resolution, and threshold limits. Other features are:
minimum and maximum temperature monitors, wide
remote temperature measurement range (up to
+127.9375°C), diode fault detection, and temperature
alert function.
The TMP400 is available in a QSSOP-16 package.
STBY
15
V+
11
2
V+
GND
7, 8
TMP400
Interrupt
Configuration
ALERT
Consecutive Alert
Configuration Register
Status Register
N-Factor
Correction
Local
Temperature
Register
TL
Remote Temp High Limit
Remote Temp Low Limit
Temperature
Comparators
Conversion Rate
Register
Local Temp Low Limit
Local Temperature Min/Max Register
D+ 3
4
Local Temp High Limit
TR
Remote
Temperature
Register
Remote Temperature Min/Max Register
Manufacturer ID Register
D-
Device ID Register
Configuration Register
Resolution Register
SCL
SDA
14
Bus Interface
12
6
Pointer Register
10
A1
A0
1
2
3
4
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 registered trademark of Texas Instruments.
SMBus is a trademark of Intel Corp.
All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2007, Texas Instruments Incorporated
TMP400
www.ti.com
SBOS404 – DECEMBER 2007
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
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.
ORDERING INFORMATION (1)
(1)
PRODUCT
PACKAGE-LEAD
PACKAGE DESIGNATOR
PACKAGE MARKING
TMP400
QSSOP-16
DBQ
TMP400
For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
ABSOLUTE MAXIMUM RATINGS (1)
Power Supply, VS
Input Voltage, pins 3, 4, 6, 10, and 15 only
Input Voltage, pins 11, 12, and 14 only
TMP400
UNIT
7
V
–0.5 to VS + 0.5
V
–0.5 to +7
V
10
mA
Operating Temperature Range
–55 to +127
°C
Storage Temperature Range
–60 to +130
°C
+150
°C
Human Body Model (HBM)
3000
V
Charged Device Model (CDM)
1000
V
Machine Model (MM)
200
V
Input Current
Junction Temperature (TJ max)
ESD Rating
(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.
TERMINAL FUNCTIONS
PIN CONFIGURATION
PIN
QSSOP-16
Top View
NC
No internal connection
NC
1
16 NC
2
V+
Positive supply (2.7V to 5.5V)
V+
2
15 STBY
3
D+
Positive connection to remote temperature
sensor
D+
3
14 SCL
4
D–
D-
4
Negative connection to remote temperature
sensor
6
A1
Address pin
13 NC
TMP400
2
NAME DESCRIPTION
1, 5, 9,
13, 16
NC
5
12 SDA
7, 8
GND
A1
6
11 ALERT
10
A0
GND
7
10 A0
11
ALERT
GND
8
9
12
SDA
Serial data line for SMBus, open-drain;
requires pull-up resistor to V+
14
SCL
Serial clock line for SMBus, open-drain;
requires pull-up resistor to V+
15
STBY
NC
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Ground
Address pin
Alert, active low, open-drain; requires pull-up
resistor to V+
Standby pin
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SBOS404 – DECEMBER 2007
ELECTRICAL CHARACTERISTICS
At TA = –40°C to +125°C and VS = 2.7V to 5.5V, unless otherwise noted.
TMP400
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
TEMPERATURE ERROR
Local Temperature Sensor
Remote Temperature Sensor (1) (2)
TELOCAL
TEREMOTE
TA = –40°C to +125°C
±1.25
±2.5
°C
VS = 3.3V, TA = +15°C to +85°C
±0.0625
±1
°C
VS = 3.3V, TA = +15°C to +75°C, TD = –40°C to +125°C (3)
±0.0625
±1
°C
VS = 3.3V, TA = –40°C to +100°C, TD = –40°C to +125°C (3)
±1
±3
°C
TA = –40°C to +125°C, TD = –40°C to +125°C (3)
±3
±10
°C
VS = 2.7V to 5.5V
±0.2
±0.5
°C/V
115
125
ms
12
Bits
vs Supply
Local/Remote
TEMPERATURE MEASUREMENT
Conversion Time (per channel) (4)
105
Resolution
Local Temperature Sensor (programmable)
9
Remote Temperature Sensor
12
Bits
Remote Sensor Source Currents
120
µA
Medium High
60
µA
Medium Low
12
µA
6
µA
High
Series Resistance 3kΩ Maximum
Low
Remote Transistor Ideality Factor
η
TMP400 Optimized Ideality Factor
1.008
SMBus INTERFACE
Logic Input High Voltage (SCL, SDA)
VIH
Logic Input Low Voltage (SCL, SDA)
VIL
2.1
V
0.8
Hysteresis
500
SMBus Output Low Sink Current
6
Logic Input Current
–1
SMBus Input Capacitance (SCL, SDA)
mA
+1
µA
3.4
MHz
35
ms
1
µs
3
SMBus Clock Frequency
SMBus Timeout
25
V
mV
30
SCL Falling Edge to SDA Valid Time
pF
DIGITAL OUTPUTS
Output Low Voltage
VOL
IOUT = 6mA
0.15
0.4
V
High-Level Output Leakage Current
IOH
VOUT = VS
0.1
1
µA
ALERT Output Low Sink Current
ALERT Forced to 0.4V
6
mA
POWER SUPPLY
Specified Voltage Range
VS
Quiescent Current
IQ
5.5
V
0.0625 Conversions per Second
2.7
30
38
µA
Eight Conversions per Second
420
525
µA
10
µA
Serial Bus Inactive, Shutdown Mode
3
Serial Bus Active, fS = 400kHz, Shutdown Mode
90
Serial Bus Active, fS = 3.4MHz, Shutdown Mode
350
Undervoltage Lock Out
Power-On Reset Threshold
2.3
POR
µA
µA
2.4
2.6
V
1.6
2.3
V
°C
TEMPERATURE RANGE
Specified Range
–40
+125
Storage Range
–60
+130
Thermal Resistance, QSSOP
(1)
(2)
(3)
(4)
70
°C
°C/W
Tested with less than 5Ω effective series resistance and 100pF differential input capacitance.
RC = '1'.
TD is the remote temperature measured at the diode.
RES1 = '1' and RES0 = '1' for 12-bit resolution.
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SBOS404 – DECEMBER 2007
TYPICAL CHARACTERISTICS
At TA = +25°C and VS = 5.0V, unless otherwise noted.
REMOTE TEMPERATURE ERROR
vs TEMPERATURE
3.0
VS = 3.3V
TREMOTE = +25°C
2
30 Typical Units Shown
h = 1.008
RC = 1
1
0
-1
-2
2.0
1.0
0
-1.0
-2.0
-3
-3.0
-50
0
-25
25
50
75
100
125
-50
25
50
75
100
125
Figure 1.
Figure 2.
REMOTE TEMPERATURE ERROR
vs LEAKAGE RESISTANCE
REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE
(Diode-Connected Transistor, 2N3906 PNP)
2.0
RC = 1
Remote Temperature Error (°C)
Remote Temperature Error (°C)
0
Ambient Temperature, TA (°C)
40
20
R - GND
0
R - VS
-20
-40
1.5
VS = 2.7V
1.0
0.5
0
VS = 5.5V
-0.5
-1.0
-1.5
-2.0
-60
0
5
10
15
20
25
0
500
1000
1500
2000
2500
Leakage Resistance (MW )
RS ( W )
Figure 3.
Figure 4.
REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE
(GND Collector-Connected Transistor, 2N3906 PNP)
REMOTE TEMPERATURE ERROR
vs DIFFERENTIAL CAPACITANCE
2.0
3000
3
1.5
VS = 2.7V
1.0
0.5
VS = 5.5V
0
-0.5
-1.0
-1.5
-2.0
Remote Temperature Error (°C)
RC = 1
Remote Temperature Error (°C)
-25
Ambient Temperature, TA (°C)
60
2
1
0
-1
-2
-3
0
4
50 Units Shown
VS = 3.3V
Local Temperature Error (°C)
Remote Temperature Error (°C)
3
LOCAL TEMPERATURE ERROR
vs TEMPERATURE
500
1000
1500
2000
2500
3000
0
0.5
1.0
1.5
2.0
RS (W)
Capacitance (nF)
Figure 5.
Figure 6.
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2.5
3.0
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SBOS404 – DECEMBER 2007
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C and VS = 5.0V, unless otherwise noted.
TEMPERATURE ERROR
vs POWER-SUPPLY NOISE FREQUENCY
25
500
Local 100mVPP Noise
Remote 100mVPP Noise
Local 250mVPP Noise
Remote 250mVPP Noise
20
15
10
450
400
350
5
IQ (mA)
Temperature Error (°C)
QUIESCENT CURRENT
vs CONVERSION RATE
0
300
-5
200
-10
150
-15
100
-20
50
0
0.0625
-25
0
5
10
15
VS = 2.7V
0.125
0.25
0.5
1
2
4
Frequency (MHz)
Conversion Rate (conversions/sec)
Figure 7.
Figure 8.
SHUTDOWN QUIESCENT CURRENT
vs SCL CLOCK FREQUENCY
SHUTDOWN QUIESCENT CURRENT
vs SUPPLY VOLTAGE
500
8
450
7
400
8
6
350
5
300
250
IQ (mA)
IQ (mA)
VS = 5.5V
250
VS = 5.5V
200
4
3
150
2
100
1
50
VS = 3.3V
0
1k
10k
100k
1M
10M
0
2.5
SCL Clock Frequency (Hz)
3.0
3.5
4.0
4.5
5.0
5.5
VS (V)
Figure 9.
Figure 10.
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SBOS404 – DECEMBER 2007
APPLICATION INFORMATION
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
TMP400.
The TMP400 is a dual-channel digital temperature
sensor that combines a local die temperature
measurement channel and a remote junction
temperature measurement channel in a QSSOP-16
package. The TMP400 is Two-Wire and SMBus
interface-compatible, and is specified over a
temperature range of –40°C to +125°C. The TMP400
contains multiple registers for holding configuration
information, temperature measurement results,
temperature comparator maximum/minimum limits,
and status information.
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) can
be automatically programmed to be cancelled by the
TMP400 by setting the RC bit to '1' in the Resolution
Register, preventing what would otherwise result in a
temperature offset.
User-programmed high and low temperature limits
stored in the TMP400 can be used to monitor local
and remote temperatures to trigger an over/under
temperature alarm (ALERT).
A total of up to 3kΩ of series line resistance is
cancelled by the TMP400 if the RC bit is enabled,
eliminating the need for additional characterization
and temperature offset correction. Upon power-up,
the RC bit is disabled (RC = 0).
The TMP400 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 is an open-drain output that also
needs a pull−up resistor. ALERT may be shared with
See the two Remote Temperature Error vs Series
Resistance 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.
+5V
0.1mF
(1)
Transistor-connected configuration :
Series Resistance
RS
RS
(2)
3
15
2
STBY
V+
10kW
(typ)
SCL
D+
10kW
(typ)
10kW
(typ)
14
(3)
(2)
CDIFF
4
DTMP400
10
6
SDA
12
Two-Wire Bus/
SMBus Controller
A0
A1
ALERT
11
GND
(1)
7, 8
Diode-connected configuration :
RS
RS
(2)
(2)
(3)
CDIFF
(1) Diode-connected configuration provides better settling time. Transistor-connected configuration provides better series resistance
cancellation.
(2) RS should be less than 1.5kΩ in most applications.
(3) CDIFF should be less than 1000pF in most applications.
Figure 11. Basic Connections
6
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SBOS404 – DECEMBER 2007
DIFFERENTIAL INPUT CAPACITANCE
The TMP400 tolerates differential input capacitance
of up to 1000pF if RC = 1 (if RC = 0, input
capacitance can be as high as 2200pF) with minimal
change in temperature error. The effect of
capacitance on sensed remote temperature error is
illustrated in the typical characteristic curve, Remote
Temperature Error vs Differential Capacitance
(Figure 6).
byte stores the decimal fraction value of the
temperature and allows a higher measurement
resolution. 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 (Table 5).
REGISTER INFORMATION
TEMPERATURE MEASUREMENT DATA
Temperature measurement data are taken over a
default range of –55°C to +127.9375°C for both local
and remote locations.
Temperature data resulting from conversions within
the default measurement range are represented in
binary form, as shown in Table 1, Binary column.
Note that any temperature above +127.9375°C
results in a value of 127.9375 (7Fh/F0h).
Temperatures below –65°C results in a value of –65
(BF/00h). The TMP400 is specified only for ambient
temperatures ranging from –40°C to +125°C.
Parameters in the Absolute Maximum Ratings table
must be observed.
Table 1. Temperature Data Format
REMOTE TEMPERATURE REGISTER
DIGITAL OUTPUT
(BINARY)
The TMP400 contains multiple registers for holding
configuration information, temperature measurement
results, temperature comparator maximum/minimum,
limits, and status information. These registers are
described in Figure 12 and Table 2.
POINTER REGISTER
Figure 12 shows the internal register structure of the
TMP400. 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 2 describes the pointer address of
the registers available in the TMP400. The power-on
reset (POR) value of the Pointer Register is 00h
(0000 0000b).
TEMPERATURE
(°C)
HIGH BYTE
LOW BYTE
HEX
128
0111 1111
1111 0000
7F/F0
Pointer Register
127.9375
0111 1111
1111 0000
7F/F0
Local and Remote Temperature Registers
100
0110 0100
0000 0000
64/00
80
0101 0000
0000 0000
50/00
75
0100 1011
0000 0000
4B/00
Status Register
50
0011 0010
0000 0000
32/00
Configuration Register
Resolution Register
Local and Remote Limit Registers
SDA
25
0001 1001
0000 0000
19/00
0.25
0000 0000
0100 0000
00/40
0
0000 0000
0000 0000
00/00
–0.25
1111 1111
1100 0000
FF/C0
–25
1110 0111
0000 0000
E7/00
Identification Registers
–55
1100 1001
0000 0000
C9/00
Local Temperature Min/Max
–65
1011 1111
0000 0000
BF/00
Remote Temperature Min/Max
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)
Conversion Rate Register
I/O
Control
Interface
SCL
Consecutive Alert Register
Figure 12. Internal Register Structure
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Table 2. Register Map
POINTER
ADDRESS (HEX)
READ
00
(1)
(2)
8
WRITE
NA
(1)
BIT DESCRIPTIONS
POWER-ON
RESET (HEX)
D7
D6
D5
D4
D3
D2
D1
D0
REGISTER DESCRIPTIONS
00
LT11
LT10
LT9
LT8
LT7
LT6
LT5
LT4
Local Temperature
(High Byte)
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
Remote Temperature
(High Byte)
01
NA
00
02
NA
00
BUSY
LHIGH
LLOW
RHIGH
RLOW
OPEN
0
0
Status Register
03
09
00
MASK1
SD
0
0
0
0
0
0
Configuration Register
04
0A
02
0
0
0
0
R3
R2
R1
R0
Conversion Rate Register
05
0B
7F
LTH11
LTH10
LTH9
LTH8
LTH7
LTH6
LTH5
LTH4
Local Temperature High
Limit (High Byte)
06
0C
C9
LTL11
LTL10
LTL9
LTL8
LTL7
LTL6
LTL5
LTL4
Local Temperature Low Limit
(High Byte)
07
0D
7F
RTH11
RTH10
RTH9
RTH8
RTH7
RTH6
RTH5
RTH4
Remote Temperature High
Limit (High Byte)
08
0E
C9
RTL11
RTL10
RTL9
RTL8
RTL7
RTL6
RTL5
RTL4
Remote Temperature Low
Limit (High Byte)
NA
0F
XX
X (2)
X
X
X
X
X
X
X
One-Shot Start
10
NA
00
RT3
RT2
RT1
RT0
0
0
0
0
Remote Temperature
(Low Byte)
13
13
00
RTH3
RTH2
RTH1
RTH0
0
0
0
0
Remote Temperature High
Limit (Low Byte)
14
14
00
RTL3
RTL2
RTL1
RTL0
0
0
0
0
Remote Temperature Low
Limit (Low Byte)
15
NA
00
LT3
LT2
LT1
LT0
0
0
0
0
Local Temperature
(Low Byte)
16
16
00
LTH3
LTH2
LTH1
LTH0
0
0
0
0
Local Temperature High
Limit (Low Byte)
17
17
00
LTL3
LTL2
LTL1
LTL0
0
0
0
0
Local Temperature Low Limit
(Low Byte)
18
18
00
NC7
NC6
NC5
NC4
NC3
NC2
NC1
NC0
N-factor Correction
1A
1A
18
0
0
0
1
1
RC
RES1
RES0
Resolution Register
22
22
01
TO_EN
0
0
0
C2
C1
C0
0
Consecutive Alert Register
30
30
7F
LMT11
LMT10
LMT9
LMT8
LMT7
LMT6
LMT5
LMT4
Local Temperature Minimum
(High Byte)
31
31
F0
LMT3
LMT2
LMT1
LMT0
0
0
0
0
Local Temperature Minimum
(Low Byte)
32
32
80
LXT11
LXT10
LXT9
LXT8
LXT7
LXT6
LXT5
LXT4
Local Temperature Maximum
(High Byte)
33
33
00
LXT3
LXT2
LXT1
LXT0
0
0
0
0
Local Temperature Maximum
(Low Byte)
34
34
7F
RMT11
RMT10
RMT9
RMT8
RMT7
RMT6
RMT5
RMT4
Remote Temperature
Minimum (High Byte)
35
35
F0
RMT3
RMT2
RMT1
RMT0
0
0
0
0
Remote Temperature
Minimum (Low Byte)
36
36
80
RXT11
RXT10
RXT9
RXT8
RXT7
RXT6
RXT5
RXT4
Remote Temperature
Maximum (High Byte)
37
37
00
RXT3
RXT2
RXT1
RXT0
0
0
0
0
Remote Temperature
Maximum (Low Byte)
NA
FC
FF
X (2)
X
X
X
X
X
X
X
Software Reset
FE
NA
55
0
1
0
1
0
1
0
1
Manufacturer ID
FF
NA
01
0
0
0
0
0
0
0
1
Device ID
NA = not applicable; register is write- or read-only.
X = indeterminate state. Writing any value to this register indicates a software reset; see the Software Reset section.
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TEMPERATURE REGISTERS
The TMP400 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 analog-to-digital converter (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 read-only registers are
updated by the ADC each time a temperature
measurement is completed.
The TMP400 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 is output first, followed by the
low byte. Both bytes of this read operation are from
the same ADC conversion. The power-on reset value
of both temperature registers is 00h.
LIMIT REGISTERS
The TMP400 has eight 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. The power-on reset value of the
local temperature high limit is 7Fh/00h (+127°C).
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 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 C9h/00h (–55°C).
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 7Fh/00h (+127°C).
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 C9h/00h (–55°C).
STATUS REGISTER
The TMP400 has a Status Register to report the state
of the temperature comparators. Table 3 shows the
Status Register bits. The Status Register is read-only
and is read by reading from pointer address 02h.
Table 3. Status Register Format
STATUS REGISTER (Read = 02h, Write = NA)
BIT #
BIT NAME
POR VALUE
(1)
D7
D6
D5
D4
D3
D2
D1
D0
BUSY
LHIGH
LLOW
RHIGH
RLOW
OPEN
—
—
0 (1)
0
0
0
0
0
0
0
The BUSY bit will change to ‘1’ almost immediately ( 0.25V at 6µA, at the
highest sensed temperature.
2. Base-emitter voltage < 0.95V at 120µA, at the
lowest sensed temperature.
3. Base resistance < 100Ω.
4. Tight control of VBE characteristics indicated by
small variations in hFE (that is, 50 to 150).
Based on these criteria, two recommended
small-signal transistors are the 2N3904 (NPN) or
2N3906 (PNP).
MEASUREMENT ACCURACY AND THERMAL
CONSIDERATIONS
The temperature measurement accuracy of the
TMP400 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.
The local temperature sensor inside the TMP400
monitors the ambient air around the device. The
thermal time constant for the TMP400 is
approximately two seconds. This constant implies
that if the ambient air changes quickly by 100°C, it
would take the TMP400 about 10 seconds (that is,
five thermal time constants) to settle to within 1°C of
the final value. In most applications, the TMP400
package is in electrical (and therefore, thermal)
contact with the printed circuit board (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 TMP400 is
measuring. Additionally, the internal power dissipation
of the TMP400 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
TMP400 dissipates 1.82mW (PDIQ = 5.5V × 420µA).
If the ALERT pin is sinking 1mA, an additional power
of 0.4mW is dissipated (PDOUT = 1mA × 0.4V =
0.4mW). Total power dissipation is then 2.22mW
(PDIQ + PDOUT) and, with an θJA of 150°C/W, causes
the junction temperature to rise approximately
0.333°C above the ambient.
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Copyright © 2007, Texas Instruments Incorporated
Product Folder Link(s): TMP400
19
TMP400
www.ti.com
SBOS404 – DECEMBER 2007
LAYOUT CONSIDERATIONS
Remote temperature sensing on the TMP400
measures very small voltages using very low
currents; therefore, noise at the IC inputs must be
minimized. Most applications using the TMP400 will
have high digital content, with several clocks and
logic level transitions creating a noisy environment.
Layout should adhere to the following guidelines:
1. Place the TMP400 as close to the remote
junction sensor as possible.
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 19. If a multilayer PCB is used, bury these
traces between ground or VDD planes to shield
them from extrinsic noise sources. 5 mil
(0.127mm) PCB traces are recommended.
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.
4. Use a 0.1µF local bypass capacitor directly
between the V+ and GND of the TMP400, as
shown in Figure 20. 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
TMP400.
5. If the connection between the remote
temperature sensor and the TMP400 is less than
8 inches (203.2mm), use a twisted-wire pair
connection. Beyond 8 inches, use a twisted,
shielded pair with the shield grounded as close to
the TMP400 as possible. Leave the remote
sensor connection end of the shield wire open to
avoid ground loops and 60Hz pickup.
20
GND(1)
D+
(1)
Ground or V+ layer
on bottom and/or
top, if possible.
D-(1)
GND
(1)
(1) 5mil traces with 5mil spacing.
Figure 19. Example Signal Traces
0.1mF Capacitor
V+
PCB Via
GND
1
16
2
15
3
14
4
PCB Via
13
TMP400
5
12
6
11
7
10
8
9
Figure 20. Suggested Bypass Capacitor
Placement
Submit Documentation Feedback
Copyright © 2007, Texas Instruments Incorporated
Product Folder Link(s): TMP400
PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
TMP400AIDBQR
ACTIVE
SSOP
DBQ
16
2500
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
TMP400
TMP400AIDBQT
ACTIVE
SSOP
DBQ
16
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
TMP400
(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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