TM
P435
TMP435
www.ti.com
SBOS495A – MARCH 2010 – REVISED APRIL 2010
±1°C TEMPERATURE SENSOR with Series-R,
n-Factor, Automatic Beta Compensation and Programmable Addressing
Check for Samples: TMP435
FEATURES
DESCRIPTION
•
•
•
•
•
•
•
The TMP435 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.
1
234
•
•
•
•
±1°C REMOTE DIODE SENSOR
±1°C LOCAL TEMPERATURE SENSOR
AUTOMATIC BETA COMPENSATION
n-FACTOR CORRECTION
PROGRAMMABLE THRESHOLD LIMITS
TWO-WIRE/ SMBus™ SERIAL INTERFACE
MINIMUM AND MAXIMUM TEMPERATURE
MONITORS
MULTIPLE INTERFACE ADDRESSES
ALERT/THERM2 PIN CONFIGURATION
DIODE FAULT DETECTION
PIN-PROGRAMMABLE TWO-WIRE
ADDRESSING
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
TMP435
includes
beta
compensation
(correction),
series
resistance
cancellation,
programmable non-ideality factor, programmable
resolution, programmable threshold limits, minimum
and maximum temperature monitors, wide remote
temperature measurement range (up to +150°C),
diode fault detection, a temperature alert function,
and pin-programmable two-wire addressing using
3-state logic.
APPLICATIONS
•
•
•
•
•
•
•
•
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
The TMP435 is available in an MSOP-10 package.
+5V
TMP435
1
V+
SCL
2
3
SDA
9
DXN
SMBus
Controller
7
6
10
DXP
THERM
A0
GND
A1
4
5
ALERT/THERM2
8
One Channel Local
One Channel Remote
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 Corporation.
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 © 2010, Texas Instruments Incorporated
TMP435
SBOS495A – MARCH 2010 – REVISED APRIL 2010
www.ti.com
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)
(1)
PRODUCT
DESCRIPTION
TMP435
Remote Junction
Temperature Sensor
TWO-WIRE
ADDRESS
PACKAGE-LEAD
PACKAGE DESIGNATOR
PACKAGE
MARKING
Pin-programmable
MSOP-10
DGS
DTPI
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.
Power Supply, VS
Input Voltage
Pins 2, 3, 4, 5 and 8 only
Pins 7, 9, and 10 only
TMP435
UNIT
+7.0
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)
4000
V
Charged Device Model (CDM)
1000
V
Machine Model (MM)
200
V
Input Current
Junction Temperature (TJ max)
ESD Rating
(1)
2
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.
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ELECTRICAL CHARACTERISTICS
At TA = –40°C to +125°C and VS = 2.7V to 5.5V, unless otherwise noted.
TMP435
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
TEMPERATURE ERROR
Local Temperature Sensor
Remote Temperature Sensor
TELOCAL
(1)
TEREMOTE
vs Supply (Local/Remote)
TA = –40°C to +125°C
±1.25
±2.5
°C
TA = +0°C to +100°C, VS = 3.3V
±0.25
±1
°C
TA = 0°C to +100°C, TDIODE = –40°C to +150°C, VS = 3.3V
±0.25
±1
°C
TA = –40°C to +100°C, TDIODE = –40°C to +150°C, VS = 3.3V
±0.5
±1.5
°C
TA = –40°C to +125°C, TDIODE = –40°C to +150°C
±3
±5
°C
VS = 2.7V to 5.5V
±0.2
±0.5
°C/V
12
15
17
ms
RC = 1
97
126
137
ms
RC = 0
36
47
52
ms
RC = 1
72
93
100
ms
RC = 0
33
44
47
ms
TEMPERATURE MEASUREMENT
Conversion Time (per channel)
Local Channel
Remote Channel
MBeta Correction Enabled (2)
MBeta Correction Disabled
(3)
Resolution
Local Channel
12
Bits
Remote Channel
12
Bits
Remote Sensor Source Currents
High
120
mA
Medium High
60
mA
Medium Low
12
mA
Low
6
mA
Series Resistance (beta correction) (4)
1.000 (2)
Remote Transistor Ideality Factor
n
TMP435 optimized ideality factor
Beta Correction Range
b
0.1
Logic Input High Voltage (SCL, SDA)
VIH
2.1
Logic Input Low Voltage (SCL, SDA)
VIL
1.008 (3)
27
SMBus INTERFACE
0.8
Hysteresis
500
SMBus Output Low Sink Current
SDA Output Low Voltage
V
6
VOL
IOUT = 6mA
0 ≤ VIN ≤ 6V
Logic Input Current
mA
0.15
–1
SMBus Input Capacitance (SCL, SDA)
0.4
V
+1
mA
3.4
MHz
35
ms
1
ms
3
SMBus Clock Frequency
SMBus Timeout
25
V
mV
32
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
mA
ALERT/THERM2 Output Low Sink Current
THERM Output Low Sink Current
(1)
(2)
(3)
(4)
ALERT/THERM2 Forced to 0.4V
6
mA
THERM2 Forced to 0.4V
6
mA
Tested with less than 5Ω effective series resistance and 100pF differential input capacitance. TA is the ambient temperature of the
TMP435. TDIODE is the temperature at the remote diode sensor.
Beta correction configuration set to '1000' and sensor is GND collector-connected (PNP collector to ground).
Beta correction configuration set to '0111' or sensor is diode-connected (base shorted to collector).
If beta correction is disabled ('0111'), then up to 1kΩ of series line resistance is cancelled; if beta correction is enabled ('1xxx'), up to
300Ω is cancelled.
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ELECTRICAL CHARACTERISTICS (continued)
At TA = –40°C to +125°C and VS = 2.7V to 5.5V, unless otherwise noted.
TMP435
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
POWER SUPPLY
Specified Voltage Range
VS
Quiescent Current
IQ
Undervoltage Lockout
Power-On Reset Threshold
2.7
5.5
V
45
mA
0.7
1
mA
3
10
mA
0.0625 Conversions per Second, VS = 3.3V
35
Eight Conversions per Second, VS = 3.3V (5)
Serial Bus Inactive, Shutdown Mode
Serial Bus Active, fS = 400kHz, Shutdown Mode
90
Serial Bus Active, fS = 3.4MHz, Shutdown Mode
350
UVLO
2.3
POR
mA
mA
2.4
2.6
V
1.6
2.3
V
°C
TEMPERATURE RANGE
Specified Range
–40
+125
Storage Range
–60
+130
Thermal Resistance, MSOP-10
(5)
4
165
qJA
°C
°C/W
Beta correction disabled.
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DEVICE INFORMATION
DGS PACKAGE
MSOP-10
(TOP VIEW)
V+
1
10 SCL
DXP
2
9
SDA
RT/THERM2 DXN
3
8
ALERT/THERM2
A0
4
7
THERM
A1
5
6
GND
PIN ASSIGNMENTS
TMP435
NO.
NAME
1
V+
DESCRIPTION
2
DXP
Positive connection to remote temperature sensor
3
DXN
Negative connection to remote temperature sensor
4
A0
Address pin 0
5
A1
Address pin 1
6
GND
7
THERM
8
ALERT/THERM2
9
SDA
Serial data line for SMBus, open-drain; requires pull-up resistor to V+
10
SCL
Serial clock line for SMBus, open-drain; requires pull-up resistor to V+
Positive supply (2.7V to 5.5V)
Ground
Thermal flag, active low, open-drain; requires pull-up resistor to V+
Alert (reconfigurable as second thermal flag), active low, open-drain; requires pull-up resistor to V+
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TYPICAL CHARACTERISTICS
At TA = +25°C and VS = 3.3V, unless otherwise noted.
REMOTE TEMPERATURE ERROR
vs TEMPERATURE
LOCAL TEMPERATURE ERROR
vs TEMPERATURE
3
Local Temperature Error (°C)
Remote Temperature Error (°C)
3
2
1
0
-1
-2
Beta Compensation Disabled.
GND Collector-Connected Transistor with n-factor = 1.008.
-3
2
1
0
-1
-2
-3
-50
75
0
25
50
Ambient Temperature, TA (°C)
-25
100
125
-50
75
0
25
50
Ambient Temperature, TA (°C)
-25
Figure 1.
Figure 2.
REMOTE TEMPERATURE ERROR
vs LEAKAGE RESISTANCE
QUIESCENT CURRENT
vs CONVERSION RATE
150
700
100
600
100
125
4
8
RGND (Low Beta)
50
500
RGND
IQ (mA)
Remote Temperature Error (°C)
VS = 3.3V
0
-50
400
300
200
RVs
-100
100
RVs (Low Beta)
0
0.0625 0.125
-150
0
5
10
15
20
25
30
1
2
Figure 4.
SHUTDOWN QUIESCENT CURRENT
vs SCL CLOCK FREQUENCY
SHUTDOWN QUIESCENT CURRENT
vs SUPPLY VOLTAGE
500
4.0
450
3.5
3.0
350
VS = 5.5V
300
2.5
IQ (mA)
IQ (mA)
0.5
Figure 3.
400
250
200
2.0
1.5
150
1.0
100
50
0.5
VS = 3.3V
0
0
1k
10k
100k
1M
10M
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VS (V)
SCL Clock Frequency (Hz)
Figure 5.
6
0.25
Conversion Rate (conversions/s)
Leakage Resistance (MW)
Figure 6.
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TYPICAL CHARACTERISTICS (continued)
At TA = +25°C and VS = 3.3V, unless otherwise noted.
REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE
REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE
(Low-Beta Transistor)
2.5
GND Collector-Connected Transistor, 2N3906 (PNP)
(1)(2)
2
1
0
Diode-Connected Transistor, 2N3906 (PNP)
(2)
-1
NOTES (1): Temperature offset is the result of
n-factor being automatically set to 1.000.
Approximate n-factor of 2N3906 is 1.008.
(2) See Figure 11 for schematic configuration.
-2
Remote Temperature Error (°C)
Remote Temperature Error (°C)
3
2.0
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
-2.5
-3
0
100 200 300 400 500 600 700 800 900
0
1k
100
200
REMOTE TEMPERATURE ERROR
vs DIFFERENTIAL CAPACITANCE
AT +25°C, VCC = 3.3V, RS = 0Ω
REMOTE TEMPERATURE ERROR
vs DIFFERENTIAL CAPACITANCE with 45nm CPU
AT +25°C, VCC = 3.3V, RS = 0Ω, Beta = 011 (AUTO)
3
2
Low-Beta Transistor (Disabled)
GND CollectorConnected
Transistor (Disabled)
0
-1
Diode-Connected
Transistor (Auto, Disabled)
-2
500
Figure 8.
GND Collector-Connected Transistor (Auto)
1
400
Figure 7.
Remote Temperature Error (°C)
Remote Temperature Error (°C)
3
300
RS (W)
RS (W)
2
1
0
Low-Beta Transistor (Auto)
-1
-2
NOTE: See Figure 12 for schematic configuration.
-3
-3
0
0.2
0.4
0.6
0.8
1.0
1.2 1.4
1.6
1.8
2.0
2.2
0
0.2
Capacitance (nF)
0.4
0.6
0.8
1.0
1.2 1.4
1.6
1.8
2.0
2.2
Capacitance (nF)
Figure 9.
Figure 10.
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PARAMETRIC MEASUREMENT INFORMATION
TEST CIRCUITS
SERIES RESISTANCE CONFIGURATION
(a) GND Collector-Connected Transistor
RS
(1)
DXP
DXN
RS
(1)
(b) Diode-Connected Transistor
(1)
RS
DXP
DXN
RS
(1)
(1)
RS should be less than 1kΩ; see Filtering section.
Figure 11.
DIFFERENTIAL CAPACITANCE CONFIGURATION
(a) GND Collector-Connected Transistor
DXP
CDIFF
(1)
DXN
(b) Diode-Connected Transistor
DXP
CDIFF
(1)
DXN
(1)
CDIFF should be less than 2200pF; see Filtering section.
Figure 12.
8
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APPLICATION INFORMATION
The TMP435 (two-channel) is a digital temperature
sensor that combines a local die temperature
measurement channel and a remote junction
temperature measurement channel in a single
package. This device is two-wire- and SMBus
interface-compatible, and is specified over a
temperature range of –40°C to +125°C. The TMP435
contains multiple registers for holding configuration
information, temperature measurement results,
temperature comparator maximum/minimum limits,
and status information. User-programmed high and
low temperature limits stored in the TMP435 can be
used to trigger an over/under temperature alarm
(ALERT) on local and remote temperatures.
Additional thermal limits can be programmed into the
TMP435 and used to trigger another flag (THERM)
that can be used to initiate a system response to
rising temperatures.
For proper remote temperature sensing operation, the
TMP435 requires only a transistor connected
between DXP and DXN.
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 0.1mF power-supply bypass
capacitor is recommended for good local bypassing.
See Figure 13 for a typical configuration.
Beta Compensation
Previous generations of remote junction temperature
sensors were operated by controlling the emitter
current of the sensing transistor. However,
examination of the physics of a transistor shows that
VBE is actually a function of the collector current. If
beta is independent of the collector current, then VBE
may be calculated from the emitter current. In earlier
generations of processors that contained PNP
transistors connected to these temperature sensors,
controlling the emitter current provided acceptable
temperature measurement results. At 90nm process
geometry and below, the beta factor continues to
decrease and the premise that it is independent of
collector current becomes less certain.
To manage this increasing temperature measurement
error, the TMP435 controls the collector current
instead of the emitter current. The TMP435
automatically detects and chooses the correct range
depending on the beta factor of the external
transistor. This auto-ranging is performed at the
beginning of each temperature conversion in order to
correct for any changes in the beta factor as a result
of temperature variation. The device can operate a
PNP transistor with a beta factor as low as 0.1. See
the Beta Compensation Configuration Register
section for further information.
Series Resistance Cancellation
Series resistance in an application circuit that typically
results from printed circuit board (PCB) trace
resistance and remote line length is automatically
cancelled by the TMP435, preventing what would
otherwise result in a temperature offset. A total of up
to 1kΩ of series line resistance is cancelled by the
TMP435 if beta correction is disabled and up to 300Ω
of series line resistance is canceled if beta correction
is enabled, eliminating the need for additional
characterization and temperature offset correction.
See the two Remote Temperature Error vs Series
Resistance typical characteristic curves (Figure 7 and
Figure 8) for details on the effect of series resistance
on sensed remote temperature error.
Differential Input Capacitance
The TMP435 can tolerate differential input
capacitance of up to 2200pF with minimal change in
temperature error. The effect of capacitance on
sensed remote temperature error is illustrated in
Figure 9 and Figure 10, Remote Temperature Error
vs Differential Capacitance. See the Filtering section
for suggested component values where filtering
unwanted coupled signals is needed.
Temperature Measurement Data
Temperature measurement data are taken over a
default range of 0°C to +127°C for both local and
remote locations. However, measurements from
–55°C to +150°C can be made both locally and
remotely by reconfiguring the TMP435 for the
extended temperature range, as described in this
section. 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 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 (RANGE) 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.
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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 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.
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, as shown in Table 2.
The measurement resolution for both the local and
remote channels is 0.0625°C, and cannot be
adjusted.
Additionally, the TMP435 is rated only for ambient
local temperatures ranging from –40°C to +125°C.
Parameters in the Absolute Maximum Ratings table
must be observed.
+5V
(1)
Transistor-connected configuration :
1
Series Resistance
RS
RS
V+
(2)
SCL
2
(3)
(2)
CDIFF
3
10
DXP
SDA
DXN
9
SMBus
Controller
TMP435
7
6
THERM
A0
GND
A1
4
5
ALERT/THERM2
8
(1)
Diode-connected configuration :
(2)
RS
(2)
RS
CDIFF
(3)
(1)
Diode-connected configuration provides better settling time. Transistor-connected configuration provides better series
resistance cancellation.
(2)
RS (optional) should be < 1kΩ in most applications. Selection of RS depends on specific application; see Filtering
section.
(3)
CDIFF (optional) should be < 2200pF in most applications. Selection of CDIFF depends on specific application; see
Filtering section and Figure 9, Remote Temperature Error vs Differential Capacitance.
Figure 13. TMP435 Basic Connections
10
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Table 1. Temperature Data Format (Local and Remote Temperature High Bytes)
LOCAL/REMOTE TEMPERATURE REGISTER
HIGH BYTE VALUE (+1°C RESOLUTION)
STANDARD BINARY (1)
(1)
(2)
EXTENDED BINARY (2)
TEMP (°C)
BINARY
HEX
BINARY
−64
0000 0000
00
0000 0000
HEX
00
−50
0000 0000
00
0000 1110
0E
−25
0000 0000
00
0010 0111
27
0
0000 0000
00
0100 0000
40
1
0000 0001
01
0100 0001
41
5
0000 0101
05
0100 0101
45
10
0000 1010
0A
0100 1010
4A
25
0001 1001
19
0101 1001
59
50
0011 0010
32
0111 0010
72
75
0100 1011
4B
1000 1011
8B
100
0110 0100
64
1010 0100
A4
125
0111 1101
7D
1011 1101
BD
127
0111 1111
7F
1011 1111
BF
150
0111 1111
7F
1101 0110
D6
175
0111 1111
7F
1110 1111
EF
191
0111 1111
7F
1111 1111
FF
Resolution is 1°C/count. Negative numbers are represented in twos complement format.
Resolution is 1°C/count. All values are unsigned with a –64°C offset.
REGISTER INFORMATION
Table 2. Decimal Fraction Temperature Data
Format (Local and Remote Temperature Low
Bytes)
TEMPERATURE REGISTER LOW BYTE VALUE
(0.0625°C RESOLUTION) (1)
The TMP435 contain multiple registers for holding
configuration information, temperature measurement
results, temperature comparator maximum/minimum,
limits, and status information. These registers are
described in Figure 14 and in Table 3.
TEMP (°C)
STANDARD AND EXTENDED BINARY
HEX
0
0000 0000
00
0.0625
0001 0000
10
0.1250
0010 0000
20
Local and Remote Temperature Registers
0.1875
0011 0000
30
Local and Remote Limit Registers
0.2500
0100 0000
40
0.3125
0101 0000
50
0.3750
0110 0000
60
Status Register
0.4375
0111 0000
70
Configuration Register
0.5000
1000 0000
80
0.5625
1001 0000
90
0.6250
1010 0000
A0
Conversion Rate Register
0.6875
1011 0000
B0
Consecutive Alert Register
0.7500
1100 0000
C0
0.8125
1101 0000
D0
0.8750
1110 0000
E0
0.9375
1111 0000
F0
(1)
Pointer Register
THERM Hysteresis Register
Beta Correction Register
SDA
I/O
Control
Interface
SCL
Identification Registers
Figure 14. Internal Register Structure
Resolution is 0.0625°C/count. All possible values are shown.
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Table 3. TMP435 Register Map
POINTER ADDRESS
(HEX)
(1)
(2)
(3)
12
BIT DESCRIPTIONS
READ
WRITE
POWER-ON
RESET (HEX)
D7
D6
D5
D4
D3
D2
D1
D0
REGISTER
DESCRIPTIONS
00
NA (1)
00
LT11
LT10
LT9
LT8
LT7
LT6
LT5
LT4
Local Temperature
(High Byte)
01
NA
00
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
Remote
Temperature (High
Byte)
02
NA
80
BUSY
LHIGH
LLOW
RHIGH
RLOW
OPEN
RTHRM
LTHRM
Status Register
03
09
00
MASK
SD
AL/TH
0
0
RANGE
0
0
Configuration
Register 1
04
0A
07
0
0
0
0
R3
R2
R1
R0
Conversion Rate
Register
05
0B
55
LTH11
LTH10
LTH9
LTH8
LTH7
LTH6
LTH5
LTH4
Local Temperature
High Limit (High
Byte)
06
0C
00
LTL11
LTL10
LTL9
LTL8
LTL7
LTL6
LTL5
LTL4
Local Temperature
Low Limit (High
Byte)
07
0D
55
RTH11
RTH10
RTH9
RTH8
RTH7
RTH6
RTH5
RTH4
Remote
Temperature High
Limit (High Byte)
08
0E
00
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
19
19
55
RTHL7
RTHL6
RTHL5
RTHL4
RTHL3
RTHL2
RTHL1
RTHL0
Remote THERM
Limit
1A
1A
1C
0
0
0
REN
LEN
RC
0
0
Configuration
Register 2
1F
1F
00
0
0
0
0
0
0
RIMASK
LMASK
Channel Mask
20
20
55
LTHL7
LTHL6
LTHL5
LTHL4
LTHL3
LTHL2
LTHL1
LTHL0
Local THERM Limit
21
21
0A
TH7
TH6
TH5
TH4
TH3
TH2
TH1
TH0
THERM Hysteresis
22
22
70
0
CTH2
CTH1
CTH0
CALT2
CALT1
CALT0
0
Consecutive Alert
Register
25
25
08
0
0
0
0
BC3
BC2
BC1
BC0
Beta Range
Register
NA
FC
00
X (3)
X
X
X
X
X
X
X
Software Reset
FD
NA
31
0
0
1
1
0
0
0
1
TMP435 Device ID
FE
NA
55
0
1
0
1
0
1
0
1
Manufacturer ID
NA = Not applicable; register is write- or read-only.
X = Indeterminate state.
X = Undefined. Writing any value to this register initiates a software reset; see the Software Reset section.
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Pointer Register
Limit Registers
Figure 14 shows the internal register structure of the
TMP435. 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 TMP435. The power-on
reset (POR) value of the Pointer Register is 00h
(0000 0000b).
The TMP435 has 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.
Temperature Registers
The TMP435 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 for the TMP435
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 TMP435 contains circuitry to assure that a low
byte register read command returns data from the
same analog-to-digital (A/D) 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 (23h 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 A/D
conversion. The power-on reset value of both
temperature registers is 00h.
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).
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 00h/00h (0°C in standard temperature
mode; –64°C in extended mode).
The remote temperature high limit for the TMP435 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 remote temperature low limit for the TMP435 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).
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The TMP435 also has a THERM limit register for both
the local and the remote channels. These are 8-bit
registers 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.
Status Register
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).
The BUSY bit reads as ‘1’ if the ADC is making a
conversion. It reads as ‘0’ if the ADC is not
converting.
The TMP435 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 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 attempts to convert a remote
temperature.
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 20.
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.
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 20.
Table 4. TMP435 Status Register Format
TMP435 STATUS REGISTER (Read = 02h, Write = NA)
BIT #
BIT NAME
POR VALUE
(1)
14
D7
D6
D5
D4
D3
D2
D1
D0
BUSY
LHIGH
LLOW
RHIGH
RLOW
OPEN
RTHRM
LTHRM
0 (1)
0
0
0
0
0
0
0
The BUSY bit changes to ‘1’ almost immediately ( 27.0)
1.000
126ms
1111
Automatically detected diode connected sensor
1.008
93ms
0000
Manually selected range 0 (0.10 < beta < 0.5)
1.000
93ms
0001
Manually selected range 1 (0.13 < beta < 1.0)
1.000
93ms
0010
Manually selected range 2 (0.18 < beta < 2.0)
1.000
93ms
0011
Manually selected range 3 (0.3 < beta < 25)
1.000
93ms
0100
Manually selected range 4 (0.5 < beta < 50)
1.000
93ms
0101
Manually selected range 5 (1.1 < beta < 100)
1.000
93ms
0110
Manually selected range 6 (2.4 < beta < 150)
1.000
93ms
0111
Manually disabled beta correction
1.008
93ms
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n-Factor Correction Register
The TMP435 allows for a different n-factor value to
be
used
for
converting
remote
channel
measurements to temperature. The remote channel
uses sequential current excitation to extract a
differential VBE voltage measurement to determine
the temperature of the remote transistor. Equation 1
relates this voltage and temperature.
I2
nkT
VBE2 - VBE1 =
ln
q
I1
(1)
( )
The value n in Equation 1 is a characteristic of the
particular transistor used for the remote channel.
When the beta compensation configuration is set to
'0111' (beta compensation disabled) or the sensor is
diode-connected (base shorted to collector), the
n-factor used by the TMP435 is 1.008. When the beta
compensation configuration is set to '1000' (beta
compensation enabled) and the sensor is GND
collector-connected (PNP collector to ground), the
n-factor used by the TMP435 is 1.000. If the n-factor
used for the temperature conversion does not match
the characteristic of the sensor, then temperature
offset is observed. The value in the n-Factor
Correction Register may be used to adjust the
effective n-factor according to Equation 2 and
Equation 3 for disabled beta compensation or a
diode-connected sensor. Equation 4 and Equation 5
may be used for enabled beta compensation and a
GND collector-connected sensor.
1.008 ´ 300
neff =
300 - NADJUST
(2)
NADJUST = 300 -
300 ´ 1.008
neff
1.000 ´ 300
neff =
300 - NADJUST
NADJUST = 300 -
300 ´ 1.000
neff
(3)
(4)
(5)
The n-correction value must be stored in
twos-complement format, yielding an effective data
18
range from –128 to +127. Table 9 shows the n-factor
range for both 1.008 and 1.000. For the TMP435, the
n-correction value may be written to and read from
pointer address 18h. The register power-on reset
value is 00h, thus having no effect unless written to.
Table 9. n-Factor Range
NADJUST
BINARY
HEX
DECIMAL
n-FACTOR
01111111
7F
127
1.747977
00001010
0A
10
1.042759
00001000
08
8
1.035616
00000110
06
6
1.028571
00000100
04
4
1.021622
00000010
02
2
1.014765
00000001
01
1
1.011371
00000000
00
0
1.008
11111111
FF
–1
1.004651
11111110
FE
–2
1.001325
11111100
FC
–4
0.994737
11111010
FA
–6
0.988235
11111000
F8
–8
0.981818
11110110
F6
–10
0.975484
10000000
80
–128
0.706542
space
Software Reset
The TMP435 may be reset by writing any value to
Pointer Register FCh. This action restores the
power-on reset state to all of the TMP435 registers as
well as abort any conversion in process and clear the
ALERT and THERM pins.
The TMP435 also supports reset via the two-wire
general call address (00000000). The TMP435
acknowledges the general call address and responds
to the second byte. If the second byte is 00000110,
the TMP435 executes a software reset. The TMP435
does not respond to other values in the second byte.
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Consecutive Alert Register
does not trip on the measured temperature falling
edges. Allowable hysteresis values are shown in
Table 11. The default hysteresis value is 10°C,
whether the device is operating in the standard or
extended mode setting.
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/THERM2 or the THERM
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/THERM2 or
the THERM pin. Table 13 shows the consecutive
alert bits. For bit descriptions, refer to Table 10.
Identification Registers
The TMP435 allows for the two-wire bus controller to
query the device for manufacturer and device IDs to
enable the device 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 TMP435 returns 55h for the
manufacturer code. The device ID is obtained by
reading from pointer address FDh. The TMP435
returns 31h for the device ID (see Table 3). These
registers are read-only.
Table 10. Consecutive Alert Register Bit
Descriptions
BIT NAME
NUMBER OF
CONSECUTIVE
OUT-OF-LIMIT
MEASUREMENTS
CALT2/CTH2 CALT1/CTH1 CALT0/CTH0 (ALERT/THERM)
0
0
0
1
0
0
1
2
0
1
1
1
1
1
Table 11. Allowable THERM Hysteresis Values
THERM HYSTERESIS VALUE
3
TEMPERATURE
(°C)
TH[7:0]
(STANDARD
BINARY)
(HEX)
4
0
0000 0000
00
1
0000 0001
01
5
0000 0101
05
10
0000 1010
0A
25
0001 1001
19
50
0011 0010
32
4B
space.
Therm Hysteresis Register
The THERM Hysteresis Register, shown in Table 12,
stores the hysteresis value used for the THERM pin
alarm function and for the ALERT/THERM2 pin when
the AL/TH is 1. This register must be programmed
with a value that is less than the 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
75
0100 1011
100
0110 0100
64
125
0111 1101
7D
127
0111 1111
7F
150
1001 0110
96
175
1010 1111
AF
200
1100 1000
C8
225
1110 0001
E1
255
1111 1111
FF
Table 12. THERM Hysteresis Register Format
THERM HYSTERESIS REGISTER
(Read = 21h, Write = 21h, POR = 0Ah)
BIT #
BIT NAME
POR VALUE
D7
D6
D5
D4
D3
D2
D1
D0
TH7
TH6
TH5
TH4
TH3
TH2
TH1
TH0
0
0
0
0
1
0
1
0
Table 13. Consecutive Alert Register Format
CONSECUTIVE ALERT REGISTER
(READ = 22h, WRITE = 22h, POR = 70h)
BIT #
D7
D6
D5
D4
D3
D2
D1
D0
BIT NAME
0
CTH2
CTH1
CTH0
CALT2
CALT1
CALT0
0
POR VALUE
0
1
1
1
0
0
0
0
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Bus Overview
Two-Wire Interface Slave Device Addresses
The TMP435 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.
The TMP435 supports nine slave device addresses
and is available in two different fixed serial interface
addresses.
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.
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.
Serial Interface
The TMP435 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 TMP435 supports the transmission protocol for
fast (1kHz to 400kHz) and high-speed (1kHz to
3.4MHz) modes. All data bytes are transmitted MSB
first.
Serial Bus Address
To communicate with the TMP435, 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 TMP435 is 4Ch (1001100b).
20
The A1 and A0 pins, as summarized in Table 14), set
the slave device address for the TMP435.
Table 14. Two-Wire Addresses
A0
A1
ADDRESS
0
0
1001 100
0
1
1001 101
1
0
1001 110
1
1
1001 111
0
Z
1001 000
Z
0
1001 001
1
Z
1001 010
Z
1
1001 011
Z
Z
0110 111
Read/Write Operations
Accessing a particular register on the TMP435 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
TMP435 requires a value for the Pointer Register
(see Figure 16).
When reading from the TMP435, 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 17 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 TMP435 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.
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TIMING DIAGRAMS
The TMP435 is two-wire and SMBus-compatible.
Figure 15 to Figure 19 describe the various
operations on the TMP435. Bus definitions are given
below. Parameters for Figure 15 are defined in
Table 15.
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 a STOP condition. Each data transfer
terminates with a STOP or a repeated START
condition.
t(LOW)
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.
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.
tF
tR
t(HDSTA)
SCL
t(HDSTA)
t(HIGH)
t(HDDAT)
t(SUSTO)
t(SUSTA)
t(SUDAT)
SDA
t(BUF)
P
S
S
P
Figure 15. Two-Wire Timing Diagram
Table 15. Timing Diagram Definitions for Figure 15
FAST MODE
PARAMETER
HIGH-SPEED MODE
MIN
MAX
MIN
MAX
UNITS
0.4
0.001
3.4
MHZ
SCL Operating Frequency
f(SCL)
0.001
Bus Free Time Between STOP
and START Condition
t(BUF)
600
160
Hold time after repeated START
condition. After this period, the
first clock is generated.
t(HDSTA)
100
100
ns
Repeated START Condition Setup
Time
t(SUSTA)
100
100
ns
STOP Condition Setup Time
t(SUSTO)
100
100
ns
Data Hold Time
t(HDDAT)
0 (1)
0 (2)
ns
Data Setup Time
t(SUDAT)
100
10
ns
SCL Clock LOW Period
t(LOW)
1300
160
ns
SCL Clock HIGH Period
t(HIGH)
600
60
Clock/Data Fall Time
Clock/Data Rise Time
for SCLK ≤ 100kHz
(1)
(2)
tF
tR
ns
ns
300
160
ns
300
160
ns
1000
ns
For cases with fall time of SCL less than 20ns and/or the rise time or fall time of SDA less than 20ns, the hold time should be greater
than 20ns.
For cases with 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
9
9
1
SCL
¼
1
SDA
0
0
1
1
0
0(1)
P7
R/W
Start By
Master
P6
P5
P4
P3
P2
P1
P0
ACK By
TMP435
Frame 2 Pointer Register Byte
Frame 1 Two- Wire Slave Address Byte
9
1
¼
ACK By
TMP435
1
9
SCL
(Continued)
SDA
(Continued)
D6
D7
D5
D4
D3
D2
D1
D0
D7
D6
D5
D4
D3
D2
D1
D0
ACK By
TMP435
ACK By
TMP435
Stop By
Master
Frame 4 Data Byte 2
Frame 3 Data Byte 1
NOTE (1): Slave address 1001100 (TMP435) shown. See Ordering Information table for more details.
Figure 16. Two-Wire Timing Diagram for Write Word Format
1
9
1
9
SCL
SDA
1
0
0
1
1
0
0(1)
R/W
Start By
Master
P7
P6
P5
P4
P3
P2
P1
P0
ACK By
TMP435
ACK By
TMP435
Frame 1 Two-Wire Slave Address Byte
1
Frame 2 Pointer Register Byte
9
1
9
SCL
(Continued)
SDA
(Continued)
1
0
0
1
1
0
0(1)
R/W
Start By
Master
D7
D6
D5
D4
ACK By
TMP435
Frame 3 Two-Wire Slave Address Byte
D3
D2
D1
D0
From
TMP435
NACK By
Master(2)
Frame 4 Data Byte 1 Read Register
NOTES: (1) Slave address 1001100 (TMP435) shown. See Ordering Information table for more details.
(2) Master should leave SDA high to terminate a single-byte read operation.
Figure 17. Two-Wire Timing Diagram for Single-Byte Read Format
22
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1
9
1
9
SCL
SDA
0
1
0
1
1
0(1)
0
R/W
P7
Start By
Master
P6
P5
P4
P3
P2
P1
P0
ACK By
TMP435
ACK By
TMP435
Frame 1 Two-Wire Slave Address Byte
Frame 2 Pointer Register Byte
1
9
1
9
SCL
(Continued)
SDA
(Continued)
1
0
0
1
1
0(1)
0
D7
R/W
Start By
Master
D6
D5
D4
D3
ACK By
TMP435
D1
D0
From
TMP435
Frame 3 Two-Wire Slave Address Byte
1
D2
ACK By
Master
Frame 4 Data Byte 1 Read Register
9
SCL
(Continued)
SDA
(Continued)
D7
D6
D5
D4
D3
D2
D1
D0
From
TMP435
NACK By
Master(2)
Stop By
Master
Frame 5 Data Byte 2 Read Register
NOTES: (1) Slave address 1001100 (TMP435) shown. See Ordering Information table for more details.
(2) Master should leave SDA high to terminate a two-byte read operation.
Figure 18. Two-Wire Timing Diagram for Two-Byte Read Format
ALERT
1
9
1
9
SCL
SDA
0
0
0
1
Start By
Master
1
0
0
1
R/W
0
0
1
1
0
ACK By
TMP435
Frame 1 SMBus ALERT Response Address Byte
0
(1)
From
TMP435
Status
NACK By
Master
Stop By
Master
Frame 2 Slave Address Byte
NOTE (1): Slave address 1001100 (TMP435) shown. See Ordering Information table for more details.
Figure 19. Timing Diagram for SMBus ALERT
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TMP435
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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
TMP435 does not 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 TMP435 switches
the input and output filter back to fast-mode
operation.
Timeout Function
The serial interface of the TMP435 resets if either
SCL or SDA are held low for 32ms (typical) between
a START and STOP condition. If the TMP435 is
holding the bus low, it releases the bus and waits for
a START condition.
THERM and ALERT/THERM2
The TMP435 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, 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 for the TMP435 to function as
ALERT (AL/TH = 0).
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
24
minus the hysteresis value stored in the THERM
Hysteresis Register. The allowable values of
hysteresis are shown in Table 11. The default
hysteresis is 10°C. When the ALERT/THERM2 pin is
configured as a second thermal alarm (Configuration
Register: bit 7 = x, bit 5 = 1), it functions the same as
THERM, but uses the temperatures stored in the
Local/Remote Temperature High Limit Registers to
set its comparison range.
When ALERT/THERM2 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 1:
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.
SMBus Alert Function
The TMP435 supports the SMBus Alert function.
When pin 6 is configured as an alert output, the
ALERT pin of the TMP435 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 TMP435 is active, the devices
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 is high if the temperature is greater
than or equal to one of the temperature high limit
settings; this bit is low if the temperature is less than
one of the temperature low limit settings. See
Figure 20 for details of this sequence.
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THERM Limit and ALERT High Limit
Measured
Temperature
ALERT Low Limit and THERM Limit Hysteresis
THERM
ALERT
SMBus ALERT
Read
Read
Read
Time
Figure 20. SMBus Alert Timing Diagram
space
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 must clear its alert status. If the
TMP435 wins the arbitration, its ALERT pin becomes
inactive at the completion of the SMBus Alert
command. If the TMP435 loses the arbitration, the
ALERT pin remains active.
Shutdown Mode (SD)
The TMP435 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 the
typical characteristic graph, Shutdown Quiescent
Current vs Supply Voltage (Figure 6). Shutdown
mode is enabled when the SD bit of the Configuration
Register 1 is high; the device shuts down
immediately, aborting the current conversion. When
SD is low, the device maintains a continuous
conversion state.
Sensor Fault
The TMP435 can sense a fault at the DXP input that
results from incorrect diode connection or an open
circuit. 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 last valid measured 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.
When not using the remote sensor with the TMP435,
the DXP and DXN inputs must be connected together
to prevent meaningless fault warnings.
Under-Voltage Lockout
The TMP435 senses 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 TMP435 does not perform a temperature
conversion if the power supply is not valid. The last
valid measured temperature is used for the
temperature measurement result.
General Call Reset
The TMP435 supports reset via the Two-Wire
General Call address 00h (0000 0000b). The
TMP435 acknowledges the General Call address and
responds to the second byte. If the second byte is
06h (0000 0110b), the TMP435 executes a software
reset. This software reset restores the power-on reset
state to all TMP435 registers, aborts any conversion
in progress, and clears the ALERT and THERM pins.
The TMP435 takes no action in response to other
values in the second byte.
Filtering
Remote junction temperature sensors are usually
implemented in a noisy environment. Noise is
frequently generated by fast digital signals and if not
filtered properly will induce errors that can corrupt
temperature measurements. The TMP435 has a
built-in 65kHz filter on the inputs of DXP and DXN to
minimize the effects of noise. However, a differential
low-pass filter can help attenuate unwanted coupled
signals.
Exact
component
values
are
application-specific. It is also recommended that the
capacitor value remains between 0pF to 2200pF with
a series resistance less than 1kΩ.
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TMP435
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Remote Sensing
The TMP435 is designed to be used with either
discrete transistors or substrate transistors built into
processor chips and ASICs. Either NPN- or PNP-type
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
transistors
can
either
be
transistoror
diode-connected (see Figure 13).
Errors in remote temperature sensor readings are
typically the consequence of the ideality factor and
current excitation used by the TMP435 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 TMP435 uses 6mA for ILOW
and 120mA for IHIGH. The device allows 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 ideality factor for the TMP435 is
trimmed to be 1.008. For transistors whose ideality
factor does not match the TMP435, Equation 6 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).
n - 1.008
TERR =
´ [273.15 + T(°C)]
1.008
)
(
Where:
•
•
•
n = Ideality factor of remote temperature sensor
T(°C) = actual temperature
TERR = Error in TMP435 reading because n ≠
1.008
Degree delta is the same for °C and K
(6)
•
For n = 1.004 and T(°C) = 100°C:
1.004 - 1.008
TERR =
´ (273.15 + 100°C)
1.008
(
)
TERR = 1.48°C
(7)
If a discrete transistor is used as the remote
temperature sensor with the TMP435, the best
accuracy can be achieved by selecting the transistor
according to the following criteria:
1. Base-emitter voltage > 0.25V at 6mA, at the
highest sensed temperature.
2. Base-emitter voltage < 0.95V at 120mA, at the
lowest sensed temperature.
26
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
TMP435 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 is 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 TMP435
monitors the ambient air around the device. The
thermal time constant for the TMP435 is
approximately two seconds. This constant implies
that if the ambient air changes quickly by 100°C, it
would take the TMP435 about 10 seconds (that is,
five thermal time constants) to settle to within 1°C of
the final value. In most applications, the TMP435
package is in 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 TMP435 is
measuring. Additionally, the internal power dissipation
of the TMP435 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
TMP435 dissipates 1.82mW (PDIQ = 5.5V × 330mA).
If both the ALERT/THERM2 and THERM pins are
each sinking 1mA, an additional power of 0.8mW is
dissipated (PDOUT = 1mA × 0.4V + 1mA × 0.4V =
0.8mW). Total power dissipation is then 2.62mW
(PDIQ + PDOUT) and, with a qJA of 165°C/W, causes
the junction temperature to rise approximately
0.432°C above the ambient.
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Layout Considerations
Remote temperature sensing on the TMP435
measures very small voltages using very low
currents; therefore, noise at the IC inputs must be
minimized. Most applications using the TMP435 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 TMP435 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 21. If a multilayer PCB is used,
bury these traces between ground or VDD planes
to shield them from extrinsic noise sources. 5 mil
(0,127 mm) 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 DXP and DXN
connections to cancel any thermocouple effects.
4. Use a 0.1mF local bypass capacitor directly
between the V+ and GND of the TMP435.
Figure 22 shows the suggested bypass capacitor
placement for the TMP435. Minimize filter
capacitance between DXP and DXN to 2200pF or
less for optimum measurement performance. This
capacitance includes any cable capacitance
between the remote temperature sensor and
TMP435.
5. If the connection between the remote
temperature sensor and the TMP435 is less than
8 inches (20,32 cm), use a twisted-wire pair
connection. Beyond 8 inches, use a twisted,
shielded pair with the shield grounded as close to
the TMP435 as possible. Leave the remote
sensor connection end of the shield wire open to
avoid ground loops and 60Hz pickup.
6. Thoroughly clean and remove all flux residue in
and around the pins of the TMP435 to avoid
temperature offset readings as a result of leakage
paths between DXP or DXN and GND, or
between DXP or DXN and V+.
V+
DXP
Ground or V+ layer
on bottom and/or
top, if possible.
DXN
GND
Note:
Use 5mil (.005in, or 0,127mm) traces with
5mil spacing.
Figure 21. Example Signal Traces
0.1mF Capacitor
V+
GND
PCB Via
1
10
DXP
2
9
DXN
3
8
A0
4
7
A1
5
6
PCB Via
TMP435
Figure 22. Suggested Bypass Capacitor
Placement
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TMP435
SBOS495A – MARCH 2010 – REVISED APRIL 2010
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REVISION HISTORY
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Original (March, 2010) to Revision A
Page
•
Changed typo in second paragraph of Beta Compensation Configuration Register section to clarify state of beta
correction ............................................................................................................................................................................ 17
•
Corrected POR value in Table 7 ......................................................................................................................................... 17
•
Corrected Equation 7 .......................................................................................................................................................... 26
28
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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)
TMP435ADGSR
ACTIVE
VSSOP
DGS
10
2500
RoHS & Green NIPDAU | NIPDAUAG
Level-2-260C-1 YEAR
-40 to 125
DTPI
TMP435ADGST
ACTIVE
VSSOP
DGS
10
250
RoHS & Green NIPDAU | NIPDAUAG
Level-2-260C-1 YEAR
-40 to 125
DTPI
(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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