TMP421AIDCNRG4 [BB]
【1∑C Remote and Local TEMPERATURE SENSOR in SOT23-8; 【 1ΣC在SOT23-8远程和本地温度传感器
| 型号： | TMP421AIDCNRG4 |
| 厂家： | 
BURR-BROWN CORPORATION |
| 描述： | 【1∑C Remote and Local TEMPERATURE SENSOR in SOT23-8 |
| 文件： | 总26页 (文件大小：576K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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TMP422
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
±1°C Remote and Local TEMPERATURE SENSOR
in SOT23-8
1
FEATURES
DESCRIPTION
2345
•
SOT23-8 PACKAGE
The TMP421 and TMP422 are remote temperature
sensor monitors with a built-in local temperature
•
•
•
•
•
•
•
•
±1°C REMOTE DIODE SENSOR (MAX)
±1.5°C LOCAL TEMPERATURE SENSOR (MAX)
SERIES RESISTANCE CANCELLATION
n-FACTOR CORRECTION
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.
TWO-WIRE/SMBus™ SERIAL INTERFACE
MULTIPLE INTERFACE ADDRESSES
DIODE FAULT DETECTION
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
configure the device.
RoHS COMPLIANT AND NO Sb/Br
APPLICATIONS
•
the TMP421 and TMP422 include series resistance
cancellation, programmable non-ideality factor, wide
remote temperature measurement range (up to
+150°C), and diode fault detection.
PROCESSOR/FPGA TEMPERATURE
MONITORING
•
•
•
•
LCD/DLP®/LCOS PROJECTORS
SERVERS
The TMP421 and TMP422 are both available in an
8-lead, SOT23 package.
CENTRAL OFFICE TELECOM EQUIPMENT
STORAGE AREA NETWORKS (SAN)
V+
V+
TMP421
TMP422
8
5
8
V+
V+
Configuration
Register
Configuration
Register
5
Status
Register
Status
Register
GND
GND
N-Factor
Correction
N-Factor
Correction
Manufacturer
ID Register
Manufacturer
ID Register
Local
Temperature
Register
Local
Temperature
Register
Device
ID Register
Device
ID Register
Conversion
Rate
Register
Conversion
Rate
Register
Configuration
Register
Configuration
Register
1
2
DX1
DX2
1
2
DXP
DXN
Remote
Temperature
Register
Resolution
Register
Resolution
Register
Remote
Temperature
Register
3
4
A1
A0
3
4
DX3
DX4
Pointer
Register
Pointer
Register
Bus
Interface
Bus
Interface
SDA
SDA
SCL
7
SCL
7
6
6
1
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.
2
3
4
5
DLP is a registered trademark of Texas Instruments.
SMBus is a trademark of Intel Corporation.
I2C is a trademark of NXP Semiconductors.
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
TMP421
TMP422
www.ti.com
SBOS398A–JULY 2007–REVISED SEPTEMBER 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.
PACKAGE INFORMATION(1)
I2C™
ADDRESS
PACKAGE
DESIGNATOR
PACKAGE
MARKING
PRODUCT
DESCRIPTION
PACKAGE-LEAD
Single-Channel
Remote Junction
Temperature Sensor
TMP421
100 11xx
100 11xx
SOT23-8
DCN
DCN
DACI
DADI
Dual Channel
Remote Junction
Temperature Sensor
TMP422
SOT23-8
(1) 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)
Over operating free-air temperature range, unless otherwise noted.
TMP420, TMP421
+7
UNIT
V
Power Supply, VS
Input Voltage
Pins 1, 2, 3, and 4 only
Pins 6 and 7 only
–0.5 to VS + 0.5
–0.5 to 7
10
V
V
Input Current
mA
°C
°C
°C
V
Operating Temperature Range
Storage Temperature Range
Junction Temperature (TJ max)
–55 to +127
–60 to +130
+150
Human Body Model (HBM)
3000
ESD Rating
Charged Device Model (CDM)
Machine Model (MM)
1000
V
200
V
(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 implied.
2
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TMP421
TMP422
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
ELECTRICAL CHARACTERISTICS
At TA = –40°C to +125°C and VS = 2.7V to 5.5V, unless otherwise noted.
TMP421, TMP422
PARAMETER
TEMPERATURE ERROR
CONDITIONS
MIN
TYP
MAX
UNIT
Local Temperature Sensor
TELOCAL
TA = –40°C to +125°C
TA = +15°C to +85°C, VS = 3.3V
±1.25
±0.25
±0.25
±1
±2.5
±1.5
±1
°C
°C
Remote Temperature Sensor(1)
TEREMOTE
TA = +15°C to +85°C, TD = –40°C to +150°C, VS = 3.3V
TA = –40°C to +100°C, TD = –40°C to +150°C, VS = 3.3V
TA = –40°C to +125°C, TD = –40°C to +150°C
VS = 2.7V to 5.5V
°C
±3
°C
±3
±5
°C
vs Supply (Local/Remote)
TEMPERATURE MEASUREMENT
Conversion Time (per channel)
Resolution
±0.2
±0.5
°C/V
100
115
130
ms
Local Temperature Sensor (programmable)
Remote Temperature Sensor
Remote Sensor Source Currents
High
12
12
Bits
Bits
Series Resistance 3kΩ Max
120
60
μA
μA
μA
μA
Medium High
Medium Low
12
Low
6
Remote Transistor Ideality Factor
SMBus INTERFACE
η
TMP421/TMP422 Optimized Ideality Factor
1.008
Logic Input High Voltage (SCL, SDA)
Logic Input Low Voltage (SCL, SDA)
Hysteresis
VIH
VIL
2.1
V
V
0.8
500
0.15
3
mV
mA
V
SMBus Output Low Sink Current
SDA Output Low Voltage
Logic Input Current
6
VOL
IOUT = 6mA
0.4
+1
0 ≤ VIN ≤ 6V
–1
μA
pF
MHz
ms
μs
SMBus Input Capacitance (SCL, SDA)
SMBus Clock Frequency
SMBus Timeout
3.4
35
1
25
30
SCL Falling Edge to SDA Valid Time
DIGITAL INPUTS
Input Capacitance
3
pF
Input Logic Levels
Input High Voltage
VIH
VIL
IIN
0.7(V+)
–0.5
(V+)+0.5
0.3(V+)
1
V
V
Input Low Voltage
Leakage Input Current
POWER SUPPLY
0V ≤ VIN ≤ VS
μA
Specified Voltage Range
Quiescent Current
VS
IQ
2.7
5.5
38
V
0.0625 Conversions per Second
8 Conversions per Second
32
400
3
μA
μA
μA
μA
μA
V
525
10
Serial Bus Inactive, Shutdown Mode
Serial Bus Active, fS = 400kHz, Shutdown Mode
Serial Bus Active, fS = 3.4MHz, Shutdown Mode
90
350
2.4
1.6
Undervoltage Lockout
Power-On Reset Threshold
TEMPERATURE RANGE
Specified Range
UVLO
POR
2.3
2.6
2.3
V
–40
–60
+125
+130
°C
°C
Storage Range
Thermal Resistance, SOT23
θJA
100
°C/W
(1) Tested with less than 5Ω effective series resistance and 100pF differential input capacitance.
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
TMP421 PIN CONFIGURATION
DCN PACKAGE
SOT23-8
(TOP VIEW)
V+
DXP
DXN
A1
1
2
3
4
8
7
6
5
SCL
TMP421
SDA
GND
A0
TMP421 PIN ASSIGNMENTS
TMP421
NO.
1
NAME
DXP
DXN
A1
DESCRIPTION
Positive connection to remote temperature sensor.
Negative connection to remote temperature sensor.
Address pin
2
3
4
A0
Address pin
5
GND
SDA
SCL
V+
Ground
6
Serial data line for SMBus, open-drain; requires pull-up resistor to V+.
Serial clock line for SMBus, open-drain; requires pull-up resistor to V+.
Positive supply voltage (2.7V to 5.5V)
7
8
TMP422 PIN CONFIGURATION
DCN PACKAGE
SOT23-8
(TOP VIEW)
V+
DX1
DX2
DX3
DX4
1
2
3
4
8
7
6
5
SCL
TMP422
SDA
GND
TMP422 PIN ASSIGNMENTS
TMP422
NO.
1
NAME
DX1
DX2
DX3
DX4
GND
SDA
SCL
V+
DESCRIPTION
Channel 1 remote temperature sensor connection pin. Also sets the TMP422 address; see Table 10.
Channel 1 remote temperature sensor connection pin. Also sets the TMP422 address; see Table 10.
Channel 2 remote temperature sensor connection pin. Also sets the TMP422 address; see Table 10.
Channel 2 remote temperature sensor connection pin. Also sets the TMP422 address; see Table 10.
Ground
2
3
4
5
6
Serial data line for SMBus, open-drain; requires pull-up resistor to V+.
Serial clock line for SMBus, open-drain; requires pull-up resistor to V+.
Positive supply voltage (2.7V to 5.5V)
7
8
4
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TMP421
TMP422
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
TYPICAL CHARACTERISTICS
At TA = +25°C and VS = +5.0V, unless otherwise noted.
REMOTE TEMPERATURE ERROR
vs TEMPERATURE
LOCAL TEMPERATURE ERROR
vs TEMPERATURE
3
3.0
2.0
VS = 3.3V
TREMOTE = +25°C
50 Units Shown
VS = 3.3V
2
1
30 Typical Units Shown
h = 1.008
1.0
0
0
-1
-2
-3
-1.0
-2.0
-3.0
-50
-25
0
25
50
75
100
125
-50
-25
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)
2.0
60
1.5
40
20
VS = 2.7V
1.0
0.5
R -GND
R -VS
0
0
VS = 5.5V
-0.5
-1.0
-1.5
-2.0
-20
-40
-60
0
5
10
15
20
25
30
0
500
1000
1500
2000
2500
3000
3500
Leakage Resistance (MW)
RS (W)
Figure 3.
Figure 4.
REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE
REMOTE TEMPERATURE ERROR
vs DIFFERENTIAL CAPACITANCE
(GND Collector-Connected Transistor, 2N3906 PNP)
2.0
3
2
1.5
VS = 2.7V
1.0
1
0.5
VS = 5.5V
0
0
-0.5
-1.0
-1.5
-2.0
-1
-2
-3
0
0.5
1.0
1.5
2.0
2.5
3.0
0
500
1000
1500
2000
2500
3000
3500
Capacitance (nF)
RS (W)
Figure 5.
Figure 6.
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C and VS = +5.0V, unless otherwise noted.
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
20
15
Remote 100mVPP Noise
Local 250mVPP Noise
Remote 250mVPP Noise
10
5
VS = 5.5V
0
-5
-10
-15
-20
-25
VS = 2.7V
0
0.0625 0.125 0.25
0
5
10
15
0.5
1
2
4
8
Frequency (MHz)
Conversion Rate (conversions/sec)
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
1M 10M
0
1k
10k
100k
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SCL CLock Frequency (Hz)
VS (V)
Figure 9.
Figure 10.
6
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
APPLICATION INFORMATION
For proper remote temperature sensing operation, the
TMP421 requires only transistor connected
The
(three-channel) are digital temperature sensors that
combine local die temperature measurement
channel and one or two remote junction temperature
measurement channels in a single SOT23-8 package.
The TMP421/22 are Two-Wire- and SMBus
TMP421
(two-channel)
and
TMP422
a
between DXP and DXN; the TMP422 requires
transistors connected between DX1 and DX2 and
between DX3 and DX4. . The SCL and SDA interface
pins require pull-up resistors as part of the
communication bus. A 0.1μF power-supply bypass
capacitor is recommended for good local bypassing.
Figure 11 shows a typical configuration for the
TMP421, and Figure 12 for the TMP422.
a
interface-compatible and are specified over
a
temperature range of –40°C to +125°C. The
TMP421/22 contain multiple registers for holding
configuration
information
and
temperature
measurement results.
+5V
Transistor-connected configuration:(1)
0.1mF
10kW
(typ)
10kW
(typ)
Series Resistance
(2)
RS
8
V+
7
6
1
2
SCL
SDA
DXP
(3)
SMBus
Controller
(2)
CDIFF
RS
DXN
A1
TMP421
3
4
A0
GND
5
Diode-connected configuration(1)
(2)
RS
:
(3)
(2)
CDIFF
RS
(1) Diode-connected configuration provides better settling time.
Transistor-connected configuration provides better series resistance cancellation.
(2) RS should be < 1.5kW in most applications.
NOTES:
(3) CDIFF should be < 1000pF in most applications.
Figure 11. TMP421 Basic Connections
+5V
Transistor-connected configuration:(1)
Series Resistance
(2)
0.1mF
10kW
(typ)
10kW
(typ)
8
RS
V+
7
6
1
2
DX1(4)
DX2(4)
SCL
SDA
DXP1
(3)
(2)
SMBus
Controller
CDIFF
RS
DXN1
DXN2
(2)
(2)
TMP422
RS
RS
3
4
DX3(4)
DX4(4)
DXP2
(3)
CDIFF
GND
5
Diode-connected configuration(1)
:
(2)
RS
(1) Diode-connected configuration provides better settling time.
Transistor-connected configuration provides better series resistance cancellation.
(2) RS should be < 1.5kW in most applications.
NOTES:
(3)
(2)
CDIFF
RS
(3) CDIFF should be < 1000pF in most applications.
(4) TMP422 SMBus slave address is 1001 100 when connected as shown.
Figure 12. TMP422 Basic Connections
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
Table 1. Temperature Data Format (Local and
Remote Temperature High Bytes)
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
LOCAL/REMOTE TEMPERATURE REGISTER
HIGH BYTE VALUE (1°C RESOLUTION)
STANDARD BINARY
EXTENDED BINARY
TEMP
automatically
cancelled
by
the
TMP421/22,
(°C)
BINARY
HEX
C0
CE
E7
00
BINARY
HEX
00
preventing what would otherwise result in
a
–64
–50
–25
0
1100 0000
1100 1110
1110 0111
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
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
temperature offset. A total of up to 3kΩ of series line
resistance is cancelled by the TMP421/22, eliminating
the need for additional characterization and
temperature offset correction. See the two Remote
Temperature Error vs Series Resistance typical
characteristic curves (Figure 4 and Figure 5) for
details on the effect of series resistance and
power-supply voltage on sensed remote temperature
error.
0E
27
40
1
01
41
5
05
45
10
0A
19
4A
59
25
50
32
72
75
4B
64
8B
A4
BD
BF
D6
EF
FF
DIFFERENTIAL INPUT CAPACITANCE
100
125
127
150
175
191
The TMP421/22 tolerate differential input capacitance
of up to 1000pF with minimal change in temperature
error. The effect of capacitance on sensed remote
temperature error is illustrated in Figure 6, Remote
Temperature Error vs Differential Capacitance.
7D
7F
7F
7F
7F
(1) Resolution is 1°C/count. Negative numbers are represented in
TEMPERATURE MEASUREMENT DATA
Two's Complement format.
Temperature measurement data are taken over a
default range of –55°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 TMP421/22 for the extended
temperature range. To change the TMP421 and
TMP422 configuration from the standard to the
extended temperature range, switch bit 2 (RANGE) of
the Configuration Register from low to high.
(2) Resolution is 1°C/count. All values are unsigned with a –64°C
offset.
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 both the local and remote channels is
0.0625°C, and is not adjustable.
Temperature data resulting from conversions within
the default measurement range are represented in
binary form, as shown in Table 1, Standard Binary
column. Note that any temperature below –64°C
results in a data value of –64 (C0h). 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
Configuration Register 1 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 the Extended Binary column of Table 1.
Standard Binary Temperature Data Calculation
Example
For positive temperatures (for example, 20°C):
(20°C)/(1°C/count) = 20 → 14h → 0001 0100
Two's Complement is not performed on positive
numbers. Simply convert the number to binary
code with 8-bit, right-justified format, and
MSB = '0' to denote a positive sign.
20°C is stored as 0001 0100 → 14h.
For negative temperatures (for example, –20C):
(|–20|)/(1°C/count) = 20 → 14h → 0001 0100
This
configuration
allows
measurement
of
Generate the Two's Complement of a negative
number by complementing the absolute value
binary number and adding 1.
temperatures as low as –64°C, and as high as
+191°C; however, most temperature-sensing diodes
only measure with the range of –55°C to +150°C.
Additionally, the TMP421/22 are rated only for
ambient temperatures ranging from –40°C to +125°C.
Parameters in the Absolute Maximum Ratings table
must be observed.
–20°C is stored as 1110 1100 → ECh.
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
Table 2. Decimal Fraction Temperature Data
Format (Local and Remote Temperature Low
Bytes)
POINTER REGISTER
Figure 13 shows the internal register structure of the
TMP421/22. 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
TEMPERATURE REGISTER LOW BYTE VALUE
(0.0625°C RESOLUTION)(1)
TEMP
(°C)
STANDARD AND EXTENDED BINARY
0000 0000
HEX
00
10
20
30
40
50
60
70
80
90
A0
B0
C0
D0
E0
F0
0
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
0.9385
0001 0000
0010 0000
the Pointer Register before executing
a
read
0011 0000
command. Table 3 describes the pointer address of
the TMP421/22 registers. The power-on reset (POR)
value of the Pointer Register is 00h (0000 0000b).
0100 0000
0101 0000
0110 0000
0111 0000
Pointer Register
1000 0000
Local and Remote Temperature Registers
1001 0000
Status Register
SDA
1010 0000
1011 0000
Configuration Registers
1100 0000
One-Shot Start Register
Conversion Rate Register
N-Factor Correction Registers
Identification Registers
Software Reset
I/O
Control
Interface
1101 0000
1110 0000
SCL
1111 0000
(1) Resolution is 0.0625°C/count. All possible values are shown.
REGISTER INFORMATION
The TMP421/22 contain multiple registers for holding
configuration information, temperature measurement
results, and status information. These registers are
described in Figure 13 and Table 3.
Figure 13. Internal Register Structure
Table 3. Register Map
BIT DESCRIPTION
POINTER
(HEX)
POR
(HEX)
7
LT11
RT11
RT11
BUSY
0
6
LT10
RT10
RT10
0
5
LT9
RT9
RT9
0
4
LT8
RT8
RT8
0
3
LT7
RT7
RT7
0
2
LT6
RT6
RT6
0
1
LT5
RT5
RT5
0
0
LT4
RT4
RT4
0
REGISTER DESCRIPTION
Local Temperature (High Byte)(1)
Remote Temperature 1 (High Byte)(1)
Remote Temperature 2 (High Byte)(1)(2)
Status Register
00
01
02
08
09
0A
0B
0F
10
11
12
21
22
FC
FE
00
00
00
00
1C/3C(2)
07
SD
0
0
0
0
RANGE
RC
R2
X
0
0
Configuration Register 1
Configuration Register 2
Conversion Rate Register
One-Shot Start(3)
0
REN2(2)
REN
0
LEN
0
0
0
0
0
0
R1
R0
X
X
X
X
X
X
X
00
00
00
00
00
LT3
RT3
RT3
NC7
NC7
X
LT2
RT2
RT2
NC6
NC6
X
LT1
RT1
RT1
NC5
NC5
X
LT0
RT0
RT0
NC4
NC4
X
0
0
nPVLD
nPVLD
nPVLD
NC1
NC1
X
0
Local Temperature (Low Byte)
Remote Temperature 1 (Low Byte)
Remote Temperature 2 (Low Byte)(2)
N Correction 1
N Correction 2(2)
Software Reset(4)
0
0
OPEN
OPEN
NC0
NC0
X
0
0
NC3
NC3
X
NC2
NC2
X
55
21
0
1
0
1
0
1
0
1
Manufacturer ID
0
0
1
0
0
0
0
1
TMP421 Device ID
FF
0
0
1
0
0
0
1
0
TMP422 Device ID
(1) Compatible with Two-Byte Read; see Figure 18.
(2) TMP422 only.
(3) X = undefined. Writing any value to this register initiates a one-shot start; see the One-Shot Conversion section.
(4) X = undefined. Writing any value to this register initiates a software reset; see the Software Reset section.
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TEMPERATURE REGISTERS
STATUS REGISTER
The TMP421/22 have 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 10h. The remote channel
high byte is at address 01h; the remote channel low
byte address is 11h. For the TMP422, the second
remote channel high byte address is 02h; the second
remote channel low byte is 12h. These registers are
read-only and are updated by the ADC each time a
temperature measurement is completed.
The Status Register reports the state of the
temperature ADCs. Table shows the Status
Register bits. The Status Register is read-only, and is
read accessing pointer address 08h.
4
The BUSY bit = '1' if the ADC is making a conversion;
it is set to '0' if the ADC is not converting.
CONFIGURATION REGISTER 1
Configuration Register 1 (pointer address 09h) sets
the temperature range and controls shutdown mode.
The Configuration Register is set by writing to pointer
address 09h and read by reading from pointer
address 09h.
The shutdown (SD) bit (bit 6) enables or disables the
temperature measurement circuitry. If SD = '0', the
TMP421/22 converts continuously at the rate set in
the conversion rate register. When SD is set to '1',
the TMP421/22 stops converting when the current
conversion sequence is complete and enters a
shutdown mode. When SD is set to '0' again, the
TMP421/22 resumes continuous conversions. When
SD = '1', a single conversion can be started by writing
to the One-Shot Register.
The TMP421/22 contain 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 (02h for the second 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 all
temperature registers is 00h.
The temperature range is set by configuring bit 2 of
the Configuration Register. Setting this bit low
configures the TMP421/22 for the standard
measurement range (–55°C to +127°C); temperature
conversions will be stored in the standard binary
format. Setting bit 2 high configures the TMP421/22
for the extended measurement range (–55°C to
+150°C); temperature conversions will be stored in
the extended binary format (see Table 1).
Table 4. Status Register Format
STATUS REGISTER (Read = 08h, Write = NA)
BIT #
BIT NAME
D7
BUSY
0(1)
D6
0
D5
0
D4
0
D3
0
D2
0
D1
0
D0
0
POR VALUE
0
0
0
0
0
0
0
(1) FOR TMP421: The BUSY changes to '1' almost immediately (< 100μs) following power-up, as the TMP421 begins the first temperature
conversion. It is high whenever the TMP421 converts a temperature reading.
FOR TMP422: The BUSY bit changes to '1' approximately 1ms following power-up. It is high whenever the TMP422 converts a
temperature reading.
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The remaining bits of the Configuration Register are
reserved and must always be set to '0'. The power-on
The LEN bit enables the local temperature
measurement channel. If LEN = '1', the local channel
is enabled; if LEN = '0', the local channel is disabled.
reset value for this register is 00h. Table
summarizes the bits of the Configuration Register.
5
The REN bit enables external temperature
measurement channel 1 (connected to pins 1 and 2.)
If REN = '1', the external channel is enabled; if REN =
'0', the external channel is disabled.
CONFIGURATION REGISTER 2
Configuration Register
2 (pointer address 0Ah)
controls which temperature measurement channels
are enabled and whether the external channels have
the resistance correction feature enabled or not.
For the TMP422 only, the REN2 bit enables the
second external measurement channel (connected to
pins 3 and 4.) If REN2 = '1', the second external
channel is enabled; if REN = '0', the second external
channel is disabled.
The RC bit enables the resistance correction feature
for the external temperature channels. If RC = '1',
series resistance correction is enabled; if RC = '0',
resistance correction is disabled. Resistance
correction should be enabled for most applications.
However, disabling the resistance correction may
yield slightly improved temperature measurement
noise performance, and reduce conversion time by
about 50%, which could lower power consumption
when conversion rates of two per second or less are
selected.
The temperature measurement sequence is local
channel, external channel 1, external channel 2,
shutdown, and delay (to set conversion rate, if
necessary). The sequence starts over with local
channel. If any of the channels are disabled, they are
skipped in the sequence.
Table 5. Configuration Register 1 Bit Descriptions
CONFIGURATION REGISTER 1 (Read/Write = 09h, POR = 00h)
BIT
NAME
FUNCTION
POWER-ON RESET VALUE
7
Reserved
—
0
0 = Run
1 = Shut Down
6
5, 4, 3
2
SD
Reserved
0
0
0
0
—
0 = –55°C to +127°C
1 = –55°C to +150°C
Temperature Range
Reserved
1, 0
—
Table 6. Configuration Register 2 Bit Descriptions
CONFIGURATION REGISTER 2 (Read/Write = 0Ah, POR = 1Ch for TMP421; 3Ch for TMP422)
BIT
NAME
FUNCTION
POWER-ON RESET VALUE
7, 6
Reserved
—
0
0 = External Channel 2 Disabled
1 = External Channel 2 Enabled
1 (TMP422)
0 (TMP421)
5
4
3
REN2
REN
LEN
0 = External Channel 1 Disabled
1 = External Channel 1 Enabled
1
1
0 = Local Channel Disabled
1 = Local Channel Enabled
0 = Resistance Correction Disabled
1 = Resistance Correction Enabled
2
RC
1
0
1, 0
Reserved
—
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CONVERSION RATE REGISTER
ONE-SHOT CONVERSION
The Conversion Rate Register (pointer address 0Bh)
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 TMP421/22 power
dissipation to be balanced with the temperature
register update rate. Table 7 shows the conversion
rate options and corresponding current consumption.
A one-shot command can be used during the idle
time between conversions to immediately start
temperature conversions on all enabled channels.
When the TMP421/22 are in shutdown mode (SD = 1
in the Configuration Register 1), a single conversion
is started on all enabled channels by writing any
value to the One-Shot Start Register, pointer address
0Fh. This write operation starts one conversion; the
TMP421/22 return 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 TMP421/22. When the TMP421/22 are in
shutdown mode, the conversion sequence currently
in process must be completed before a one-shot
command can be issued. One-shot commands issued
during a conversion are ignored.
Table 7. Conversion Rate Register
CONVERSION RATE REGISTER (Read/Write = 0Bh, POR = 07h)
AVERAGE IQ (TYP) (μA)
R7
0
R6
0
R5
0
R4
0
R3
0
R2
0
R1
0
R0
0
CONVERSIONS/SEC
VS = 2.7V
11
VS = 5.5V
32
0.0625
0.125
0.25
0.5
0
0
0
0
0
0
0
1
17
38
0
0
0
0
0
0
1
0
28
49
0
0
0
0
0
0
1
1
47
69
0
0
0
0
0
1
0
0
1
80
103
155
220
413
0
0
0
0
0
1
0
1
2
128
190
373
0
0
0
0
0
1
1
0
4(1)
8(2)
0
0
0
0
0
1
1
1
(1) Conversion rate shown is for only one or two enabled measurement channels. When three channels are enabled, the conversion rate is
2 and 2/3 conversions-per-second.
(2) Conversion rate shown is for only one enabled measurement channel. When two channels are enabled, the conversion rate is 4
conversions-per-second. When three channels are enabled, the conversion rate is 2 and 2/3 conversions-per-second.
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n-FACTOR CORRECTION REGISTER
SOFTWARE RESET
The TMP421/22 allow for a different n-factor value to
The TMP421/22 may be reset by writing any value to
the Software Reset Register (pointer address FCh).
This action restores the power-on reset state to all of
the TMP421/22 registers as well as abort any
conversion in process. The TMP421/22 also supports
reset via the two-wire general call address (0000
0000). The TMP421/22 acknowledges the general
call address and responds to the second byte. If the
second byte is 0000 0110, the TMP421/22 executes
a software reset. The TMP421/22 takes no action in
response to other values in the second byte.
be
measurements to temperature. The remote channel
uses sequential current excitation to extract
used
for
converting
remote
channel
a
differential VBE voltage measurement to determine
the temperature of the remote transistor. Equation 1
relates this voltage and temperature.
I2
lnǒ Ǔ
I1
nkT
q
VBE2*VBE1
+
(1)
The value n in Equation 1 is a characteristic of the
particular transistor used for the remote channel. The
default value for the TMP421/22 is n = 1.008. The
value in the n-Factor Correction Register may be
used to adjust the effective n-factor according to
Equation 2 and Equation 3.
IDENTIFICATION REGISTERS
The TMP421/22 allow for the Two-Wire bus controller
to query the device for manufacturer and device IDs
to enable 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 TMP421/22 both return 55h for the
manufacturer code. The TMP421 returns 21h for the
device ID and the TMP422 returns 22h for the device
ID. These registers are read-only.
1.008 300
300 * NADJUST
neff
+
ǒ
Ǔ
(2)
300 1.008
+ 300 * ǒ
Ǔ
NADJUST
neff
(3)
The n-correction value must be stored in
two's-complement format, yielding an effective data
range from –128 to +127. The n-correction value may
be written to and read from pointer address 21h. (The
n-correction value for the second remote channel is
read to/written from pointer address 22h.) The
register power-on reset value is 00h, thus having no
effect unless the register is written to.
BUS OVERVIEW
The TMP421/22 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.
Table 8. n-Factor Range
NADJUST
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.
BINARY
HEX
7F
0A
08
DECIMAL
n
0111 1111
0000 1010
0000 1000
0000 0110
0000 0100
0000 0010
0000 0001
0000 0000
1111 1111
1111 1110
1111 1100
1111 1010
1111 1000
1111 0110
1000 0000
127
10
8
1.747977
1.042759
1.035616
1.028571
1.021622
1.014765
1.011371
1.008
06
6
04
4
02
2
01
1
00
0
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.
FF
FE
FC
FA
F8
F6
80
–1
–2
–4
–6
–8
–10
–128
1.004651
1.001325
0.994737
0.988235
0.981818
0.975484
0.706542
Once all data have been transferred, the master
generates a STOP condition. STOP is indicated by
pulling SDA from low to high, while SCL is high.
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Table 9. TMP421 Slave Address Options
SERIAL INTERFACE
TWO-WIRE SLAVE
ADDRESS
The TMP421/22 operate 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 TMP421/22 support the transmission
protocol for fast (1kHz to 400kHz) and high-speed
(1kHz to 3.4MHz) modes. All data bytes are
transmitted MSB first.
A1
A0
0011 100
0011 101
0011 110
0011 111
0101 010
1001 100
1001 101
1001 110
1001 111
Float
0
1
Float
0
Float
Float
Float
0
1
Float
0
0
1
1
1
0
SERIAL BUS ADDRESS
1
To communicate with the TMP421/22, 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 slave device address for the TMP422 is set by
the connections between the external transistors and
the TMP422 according to Figure 14 and Table 10. If
one of the channels is unused, the respective DXP
connection should be connected to GND, and the
DXN connection should be left unconnected. The
polarity of the transistor for external channel 2 (pins 3
and 4) sets the least significant bit of the slave
address. The polarity of the transistor for external
channel 1 (pins 1 and 2) sets the next least
significant bit of the slave address.
Two-Wire Interface Slave Device Addresses
The TMP421 supports nine slave device addresses
and the TMP422 supports four slave device
addresses.
The slave device address for the TMP421 is set by
the A1 and A0 pins according to Table 9.
Table 10. TMP422 Slave Address Options
TWO-WIRE SLAVE
ADDRESS
DX1
DX2
DX3
DX4
1001 100
1001 101
1001 110
1001 111
DXP1
DXP1
DXN1
DXN1
DXN1
DXN1
DXP1
DXP1
DXP2
DXN2
DXP2
DXN2
DXN2
DXP2
DXN2
DXP2
SCL
SDA
V+
DX1
DX2
DX3
DX4
V+
SCL
SDA
GND
DX1
DX2
DX3
DX4
V+
SCL
SDA
GND
DX1
DX2
DX3
DX4
V+
SCL
SDA
GND
DX1
DX2
DX3
DX4
V+
Q0
Q2
Q4
Q6
SCL
SDA
GND
Q3
Q5
Q7
Q1
Address = 1001100
Address = 1001101
Address = 1001110
Address = 1001111
Figure 14. TMP422 Connections for Setup of Device Address
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The TMP422 checks the polarity of the external
transistor at power-on, or after software reset, by
forcing current to pin 1 while connecting pin 2 to
approximately 0.6V. If the voltage on pin 1 does not
pull up to near the VDD of the TMP422, pin 1
functions as DXP for this channel, and the second
LSB of the slave address is '0'. If the voltage on pin 1
does pull up to near V+, the TMP422 forces current
to pin 2 while connecting pin 1 to 0.6V. If the voltage
on pin 2 does not pull up to near V+, the TMP422
uses pin 2 for DXP of channel 1, and sets the second
LSB of the slave address to '1'. If both pins are
shorted to GND or if both pins are open, the TMP422
uses pin 1 as DXP and sets the address bit to '0'.
This process is then repeated for channel 2 (pins 3
and 4).
When reading from the TMP421/22, 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 are
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 18 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 TMP421/22 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.
If the TMP422 is to be used with transistors that are
located on another IC (such as a CPU, DSP, or
graphics processor), it is recommended to use pin 1
or pin 3 as DXP to assure correct address detection.
If the other IC has a lower supply voltage or is not
powered when the TMP422 tries to detect the slave
address, a protection diode may turn on during the
detection process and the TMP422 may incorrectly
choose the DXP pin and slave address. Using pin 1
and/or pin 3 for transistors that are on other ICs will
ensure correction operation independent of supply
sequencing or levels.
Read operations should be terminated by issuing a
Not-Acknowledge command at the end of the last
byte to be read. For a single-byte operation, the
master should leave the SDA line high during the
Acknowledge time of the first byte that is read from
the slave. For a two-byte read operation, the master
must pull SDA low during the Acknowledge time of
the first byte read, and should leave SDA high during
the Acknowledge time of the second byte read from
the slave.
READ/WRITE OPERATIONS
Accessing a particular register on the TMP421/22 is
accomplished by writing the appropriate value to the
Pointer Register. The value for the Pointer Register is
the first byte transferred after the slave address byte
with the R/W bit low. Every write operation to the
TMP421/22 requires a value for the Pointer Register
(see Figure 16).
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TIMING DIAGRAMS
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 data transfer.
The
TMP421/22
are
Two-Wire
and
SMBus-compatible. Figure 15 to Figure 18 describe
the various operations on the TMP421/22.
Parameters for Figure 15 are defined in Table 11.
Bus definitions are:
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 can be signaled by
the master generating a Not-Acknowledge on the last
byte that has been transmitted by the slave.
Bus Idle: Both SDA and SCL lines remain high.
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
terminates with
condition.
a STOP condition. Each data transfer
a
repeated START or STOP
t(LOW)
tR
tF
t(HDSTA)
SCL
SDA
t(SUSTO)
t(HDSTA)
t(HIGH)
t(SUSTA)
t(SUDAT)
t(HDDAT)
t(BUF)
P
S
S
P
Figure 15. Two-Wire Timing Diagram
Table 11. Timing Characteristics for Figure 15
FAST MODE
HIGH-SPEED MODE
PARAMETER
MIN
0.001
600
MAX
MIN
0.001
160
MAX
UNIT
SCL Operating Frequency
f(SCL)
t(BUF)
0.4
3.4
MHz
ns
Bus Free Time Between STOP and START Condition
Hold time after repeated START condition. After this period, the first clock
is generated.
t(HDSTA)
100
100
ns
Repeated START Condition Setup Time
STOP Condition Setup Time
Data Hold Time
t(SUSTA)
t(SUSTO)
t(HDDAT)
t(SUDAT)
t(LOW)
t(HIGH)
tF
100
100
0(1)
100
100
0(2)
10
ns
ns
ns
ns
ns
ns
ns
Data Setup Time
100
1300
600
SCL Clock LOW Period
SCL Clock HIGH Period
Clock/Data Fall Time
160
60
300
300
160
160
Clock/Data Rise Time
for SCL ≤ 100kHz
tR
ns
tR
1000
(1) For cases with fall time of SCL less than 20ns and/or the rise or fall time of SDA less than 20ns, the hold time should be greater than
20ns.
(2) For cases with a fall time of SCL less than 10ns and/or the rise or fall time of SDA less than 10ns, the hold time should be greater than
10ns.
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1
1
9
1
9
SCL
SDA
¼
0
0
1
1
0
0(1) R/W
P7 P6 P5 P4 P3
P2 P1
P0
¼
Start By
Master
ACK By
ACK By
TMP421/22
TMP421/22
Frame 2 Pointer Register Byte
Frame 1 Two- Wire Slave Address Byte
1
9
1
9
SCL
(Continued)
SDA
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
ACK By
(Continued)
ACK By
Stop By
TMP421/22
TMP421/22 Master
Frame 3 Data Byte 1
Frame 4 Data Byte 2
NOTE: (1) Slave address 1001100 shown.
Figure 16. Two-Wire Timing Diagram for Write Word Format
1
9
1
9
¼
SCL
SDA
1
0
0
1
1
0
0(1)
R/W
P7
P6
P5
P4
P3
P2
P1
P0
¼
Start By
Master
ACK By
ACK By
TMP421/22
TMP421/22
Frame 1 Two-Wire Slave Address Byte
Frame 2 Pointer Register Byte
1
9
1
9
SCL
¼
¼
(Continued)
SDA
1
0
0(1)
1
0
0
1
R/W
D7
D6
D5
D4 D3
D2
D1
D0
(Continued)
Start By
Master
ACK By
From
TMP421/22
NACK By
Master(2)
TMP421/22
Frame 3 Two-Wire Slave Address Byte
Frame 4 Data Byte 1 Read Register
NOTES: (1) Slave address 1001100 shown.
(2) Master should leave SDA high to terminate a single-byte read operation.
Figure 17. Two-Wire Timing Diagram for Single-Byte Read Format
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¼
SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
1
9
1
9
SCL
0(1)
R/W
P7
P6
P5
P4
P3
P2
P1
P0
¼
SDA
1
0
0
1
1
0
Start By
Master
ACK By
ACK By
TMP421/22
TMP421/22
Frame 1 Two-Wire Slave Address Byte
Frame 2 Pointer Register Byte
1
9
1
9
SCL
¼
(Continued)
SDA
0(1)
¼
ACK By
Master
1
0
1
0
0
1
R/W
D7
D6
D5
D4 D3
D2
D1
D0
(Continued)
Start By
Master
ACK By
From
TMP421/22
TMP421/22
Frame 3 Two-Wire Slave Address Byte
Frame 4 Data Byte 1 Read Register
1
9
SCL
(Continued)
SDA
D7 D6
D5
D4
D3
D2
D1
D0
(Continued)
From
NACK By Stop By
Master(2)
Master
TMP421/22
Frame 5 Data Byte 2 Read Register
NOTES: (1) Slave address 1001100 shown.
(2) Master should leave SDA high to terminate a two-byte read operation.
Figure 18. Two-Wire Timing Diagram for Two-Byte Read Format
18
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TMP422
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
HIGH-SPEED MODE
When not using the remote sensor with the TMP421,
the DXP and DXN inputs must be connected together
to prevent meaningless fault warnings. When not
using a remote sensor with the TMP422, the DX pins
should be connected using Table 10 such that DXP
connections are grounded and DXN connections are
left open (unconnected).
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
(0000 1xxx) as the first byte after a START condition
to switch the bus to high-speed operation. The
TMP421/22 does acknowledge this byte, but switches
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 transmits a Two-Wire slave
address to initiate a data transfer operation. The bus
continues to operate in Hs-mode until a STOP
condition occurs on the bus. Upon receiving the
STOP condition, the TMP421/22 switches the input
and output filters back to fast mode operation.
UNDERVOLTAGE LOCKOUT
The TMP421/22 sense when the power-supply
voltage has reached a minimum voltage level for the
ADC to function. The detection circuitry consists of a
voltage comparator that enables the ADC after the
power supply (V+) exceeds 2.45V (typical). The
comparator output is continuously checked during a
conversion. The TMP421/22 does not perform a
temperature conversion if the power supply is not
valid. The PVLD bit (bit 1, see Table 3) of the
Local/Remote Temperature Register is set to '1' and
the temperature result may be incorrect.
TIMEOUT FUNCTION
The TMP421/22 reset the serial interface if either
SCL or SDA are held low for 30ms (typical) between
a START and STOP condition. If the TMP421/22 are
holding the bus low, it releases the bus and waits for
a START condition. To avoid activating the timeout
function, it is necessary to maintain a communication
speed of at least 1kHz for the SCL operating
frequency.
GENERAL CALL RESET
The TMP421/22 support reset via the Two-Wire
General Call address 00h (0000 0000b). The
TMP421/22 acknowledge the General Call address
and respond to the second byte. If the second byte is
06h (0000 0110b), the TMP421/22 execute
a
SHUTDOWN MODE (SD)
software reset. This software reset restores the
power-on reset state to all TMP421/22 registers, and
aborts any conversion in progress. The TMP421/22
take no action in response to other values in the
second byte.
The TMP421/22 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 TMP421/22 have
a built-in
65kHz filter on the inputs of DXP and DXN (TMP421),
or on the inputs of DX1 through DX4 (TMP422), 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 this capacitor should be
between 100pF and 1nF. Some applications attain
better overall accuracy with additional series
resistance; however, this increased accuracy is
application-specific. When series resistance is added,
the total value should not be greater than 3kΩ. If
filtering is needed, suggested component values are
100pF and 50Ω on each input; exact values are
application-specific.
SENSOR FAULT
The TMP421 can sense a fault at the DXP input
resulting from incorrect diode connection. Both the
TMP421 and the TMP422 can sense an open circuit.
Short-circuit conditions return a value of –64h. The
detection circuitry consists of a voltage comparator
that trips when the voltage at DXP exceeds
(V+) – 0.6V (typical). The comparator output is
continuously checked during a conversion. If a fault is
detected, the OPEN bit (bit 0) in the temperature
result register is set to '1' and the rest of the register
bits should be ignored.
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
REMOTE SENSING
lowest sensed temperature.
3. Base resistance < 100Ω.
The TMP421/22 are 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.
NPN transistors must be diode-connected. PNP
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).
transistors
can
either
be
transistor-
or
diode-connected (see Figure 11).
MEASUREMENT ACCURACY AND THERMAL
CONSIDERATIONS
Errors in remote temperature sensor readings are
typically the consequence of the ideality factor and
current excitation used by the TMP421/22 versus the
manufacturer-specified operating current for a given
transistor. Some manufacturers specify a high-level
and low-level current for the temperature-sensing
substrate transistors. The TMP421/22 use 6μA for
ILOW and 120μA for IHIGH. The TMP421/22 allow for
different n-factor values; see the N-Factor Correction
Register section. The ideality factor (n) is a measured
characteristic of a remote temperature sensor diode
as compared to an ideal diode.
The temperature measurement accuracy of the
TMP421/22 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 ideality factor for the TMP421/22 is trimmed to
be 1.008. For transistors that have an ideality factor
that does not match the TMP421/22, Equation 4 can
be used to calculate the temperature error. Note that
for the equation to be used correctly, actual
temperature (°C) must be converted to kelvins (K).
The local temperature sensor inside the TMP421/22
monitors the ambient air around the device. The
thermal time constant for the TMP421/22 is
approximately two seconds. This constant implies
that if the ambient air changes quickly by 100°C, it
would take the TMP421/22 about 10 seconds (that is,
five thermal time constants) to settle to within 1°C of
the final value. In most applications, the TMP421/22
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 TMP421/22 is
measuring. Additionally, the internal power dissipation
of the TMP421/22 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
n * 1.008
1.008
ǒ
ǒ
273.15 ) T °C
Ǔ
Ǔ
+ ǒ
Ǔ
TERR
(4)
Where:
n = ideality factor of remote temperature sensor
T(°C) = actual temperature
TERR = error in TMP421/22 due to n ≠ 1.008
Degree delta is the same for °C and K
For n = 1.004 and T(°C) = 100°C:
1.004 * 1.008
ǒ Ǔ
273.15 ) 100°C
+ ǒ
Ǔ
TERR
1.008
TERR + 1.48°C
(5)
If a discrete transistor is used as the remote
temperature sensor with the TMP421/22, the best
accuracy can be achieved by selecting the transistor
according to the following criteria:
TMP421/22 dissipates 2.3mW (PDIQ
= 5.5V ×
415μA). A θJA of 100°C/W causes the junction
temperature to rise approximately +0.23°C above the
ambient.
1. Base-emitter voltage > 0.25V at 6μA, at the
highest sensed temperature.
2. Base-emitter voltage < 0.95V at 120μA, at the
20
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SBOS398A–JULY 2007–REVISED SEPTEMBER 2007
LAYOUT CONSIDERATIONS
Remote temperature sensing on the TMP421/22
measures very small voltages using very low
currents; therefore, noise at the IC inputs must be
minimized. Most applications using the TMP421/22
will have high digital content, with several clocks and
logic level transitions creating a noisy environment.
Layout should adhere to the following guidelines:
V+
DXP
Ground or V+ layer
on bottom and/or
top, if possible.
DXN
1. Place the TMP421/22 as close to the remote
junction sensor as possible.
2. Route the DXP and DXN 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
PCB traces are recommended.
GND
NOTE: Use minimum 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
Figure 19. Suggested PCB Layer Cross-Section
approximate
locations
of
copper-to-solder
connections in both the DXP and DXN
connections to cancel any thermocouple effects.
0.1mF Capacitor
4. Use a 0.1μF local bypass capacitor directly
between the V+ and GND of the TMP421/22, as
shown in Figure 20. Minimize filter capacitance
between DXP and DXN to 1000pF or less for
optimum measurement performance. This
capacitance includes any cable capacitance
between the remote temperature sensor and
TMP421/22.
GND
PCB Via
V+
DXP
DXN
A1
1
2
3
4
8
7
6
5
5. If the connection between the remote
temperature sensor and the TMP421/22 is less
than 8 in long, use a twisted-wire pair connection.
Beyond 8 in, use a twisted, shielded pair with the
shield grounded as close to the TMP421/22 as
possible. Leave the remote sensor connection
end of the shield wire open to avoid ground loops
and 60Hz pickup.
A0
TMP421
0.1mF Capacitor
6. Thoroughly clean and remove all flux residue in
and around the pins of the TMP421/22 to avoid
temperature offset readings due to leakage paths
between DXP or DXN and GND, or between DXP
or DXN and V+.
GND
PCB Via
V+
DX1
DX2
DX3
DX4
1
2
3
4
8
7
6
5
TMP422
Figure 20. Suggested Bypass Capacitor
Placement and Trace Shielding
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PACKAGE OPTION ADDENDUM
www.ti.com
5-Oct-2007
PACKAGING INFORMATION
Orderable Device
TMP421AIDCNR
TMP421AIDCNRG4
TMP421AIDCNT
Status (1)
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
Package Package
Pins Package Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
Qty
Type
Drawing
SOT-23
DCN
8
8
8
8
8
8
8
8
3000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
SOT-23
SOT-23
SOT-23
SOT-23
SOT-23
SOT-23
SOT-23
DCN
DCN
DCN
DCN
DCN
DCN
DCN
3000 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)
TMP421AIDCNTG4
TMP422AIDCNR
TMP422AIDCNRG4
TMP422AIDCNT
250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
3000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
3000 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)
TMP422AIDCNTG4
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
PACKAGE MATERIALS INFORMATION
www.ti.com
4-Oct-2007
TAPE AND REEL BOX INFORMATION
Device
Package Pins
Site
Reel
Reel
A0 (mm)
B0 (mm)
K0 (mm)
P1
W
Pin1
Diameter Width
(mm) (mm) Quadrant
(mm)
179
179
179
179
(mm)
TMP421AIDCNR
TMP421AIDCNT
TMP422AIDCNR
TMP422AIDCNT
DCN
DCN
DCN
DCN
8
8
8
8
SITE 48
SITE 48
SITE 48
SITE 48
8
8
8
8
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
1.4
1.4
1.4
1.4
4
4
4
4
8
8
8
8
Q1
Q1
Q1
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
4-Oct-2007
Device
Package
Pins
Site
Length (mm) Width (mm) Height (mm)
TMP421AIDCNR
TMP421AIDCNT
TMP422AIDCNR
TMP422AIDCNT
DCN
DCN
DCN
DCN
8
8
8
8
SITE 48
SITE 48
SITE 48
SITE 48
195.0
195.0
195.0
195.0
200.0
200.0
200.0
200.0
45.0
45.0
45.0
45.0
Pack Materials-Page 2
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