ST STCN75 User Manual
Digital temperature sensor and thermal watchdog
Features
■ Measures temperatures from –55 °C to
+125 °C (–67 °F to +257 °F)
–
±0.5 °C (typ) accuracy
–
±2 °C (max) accuracy from –25 °C to
+100
°C
■ Low operating current:125 µA (typ)
■ No external components required
■ 2-wire I
– Selectable bus address allows connection
■ Wide power supply range - operating voltage
range: 2.7 V to 5.5 V
■ Conversion time is 45 ms (typ)
■ Programmable temperature threshold and
hysteresis set points
■ Pin- and software-compatible with TCN75
(drop-in replacement)
■ Power-up defaults permit standalone operation
as a thermostat
■ Shutdown mode to minimize power
consumption
■ Output pin (open drain) can be configured for
interrupt or comparator/thermostat mode (dual
purpose event pin)
■ MSOP8 (TSSOP8) package
2
C/SMBus-compatible serial interface
of up to eight devices on the bus
STCN75
Datasheet − production data
MSOP8
(TSSOP8)
March 2012 Doc ID 13307 Rev 9 1/36
This is information on a product in full production.
www.st.com
1
Contents STCN75
Contents
1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1 Serial communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2 Temperature sensor output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3 Pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.1 SDA (open drain) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.2 SCL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.3 OS
1.3.4 GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.5 A2, A1, A0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.6 V
2 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1 Applications information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
/INT (open drain) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
DD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 Thermal alarm function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3 Comparator mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.4 Interrupt mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.5 Fault tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.6 Shutdown mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.7 Temperature data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1 Registers and register set formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1.1 Command/pointer register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1.2 Configuration register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.1.3 Temperature register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1.4 Overlimit temperature register (T
3.1.5 Hysteresis temperature register (T
3.2 Power-up default conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.3 Serial interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.4 2-wire bus characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
) . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
OS
) . . . . . . . . . . . . . . . . . . . . . . . . . 18
HYS
3.4.1 Bus not busy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.4.2 Start data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.4.3 Stop data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2/36 Doc ID 13307 Rev 9
STCN75 Contents
3.4.4 Data valid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.4.5 Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.5 READ mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.6 WRITE mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4 Typical operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6 DC and AC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8 Part numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Doc ID 13307 Rev 9 3/36
List of tables STCN75
List of tables
Table 1. Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Table 2. Fault tolerance setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 3. Relationship between temperature and digital output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 4. Command/pointer register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 5. Register pointers selection summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 6. Configuration register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 7. Temperature register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 8. T
Table 9. STCN75 serial bus slave addresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 10. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Table 11. Operating and AC measurement conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Table 12. DC and AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Table 13. AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Table 14. MSOP8 (TSSOP8) – 8-lead, thin shrink small outline (3 mm x 3 mm) package
Table 15. Carrier tape dimensions for MSOP8 (TSSOP8) package. . . . . . . . . . . . . . . . . . . . . . . . . . 32
Table 16. Reel dimensions for 12 mm carrier tape - MSOP8 (TSSOP8) package . . . . . . . . . . . . . . . 33
Table 17. Ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Table 18. Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
and T
OS
mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
HYS
4/36 Doc ID 13307 Rev 9
STCN75 List of figures
List of figures
Figure 1. Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 2. Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 3. Functional block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 4. Typical 2-wire interface connections diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 5. Serial bus data transfer sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 6. Acknowledgement sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 7. Slave address location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 8. Typical 2-byte READ from preset pointer location (e.g. temp - T
Figure 9. Typical pointer set followed by an immediate READ for 2-byte register (e.g. temp). . . . . . 22
Figure 10. Typical 1-byte READ from the cofiguration register with preset pointer . . . . . . . . . . . . . . . 22
Figure 11. Typical pointer set followed by an immediate READ from the configuration register . . . . . 23
Figure 12. Configuration register WRITE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Figure 13. T
OS
and T
WRITE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
HYS
Figure 14. Temperature variation vs. voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 15. Bus timing requirements sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 16. MSOP8 (TSSOP8) – 8-lead, thin shrink small outline (3 mm x 3 mm) package
mechanical drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Figure 17. Carrier tape for MSOP8 (TSSOP8) package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Figure 18. Reel schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
OS
, T
) . . . . . . . . . . . . 22
HYS
Doc ID 13307 Rev 9 5/36
Description STCN75
1 Description
The STCN75 is a high-precision digital CMOS temperature sensor IC with a sigma-delta
temperature-to-digital converter and an I
for general applications such as personal computers, system thermal management,
electronics equipment, and industrial controllers, and is packaged in the industry-standard
8-lead TSSOP package.
The device contains a bandgap temperature sensor and 9-bit ADC which monitor and
digitize the temperature to a resolution up to 0.5 °C. The STCN75 is typically accurate to
(±3 °C - max) over the full temperature measurement range of –55 °C to 125 °C with ±2 °C
accuracy in the –25 °C to +100 °C range. The STCN75 is pin-for-pin and software
compatible with the TCN75.
The STCN75 is specified for operating at supply voltages from 2.7 V to 5.5 V. Operating at
3.3 V, the supply current is typically (125 µA).
The onboard sigma-delta analog-to-digital converter (ADC) converts the measured
temperature to a digital value that is calibrated in degrees centigrade; for Fahrenheit
applications a lookup table or conversion routine is required.
The STCN75 is factory-calibrated and requires no external components to measure
temperature.
1.1 Serial communications
The STCN75 has a simple 2-wire I2C-compatible digital serial interface which allows the
user to access the data in the temperature register at any time. It communicates via the
serial interface with a master controller which operates at speeds up to 400 kHz. Three pins
(A0, A1, and A2) are available for address selection, and enable the user to connect up to 8
devices on the same bus without address conflict.
2
C-compatible serial digital interface. It is targeted
In addition, the serial interface gives the user easy access to all STCN75 registers to
customize operation of the device.
6/36 Doc ID 13307 Rev 9
STCN75 Description
1.2 Temperature sensor output
The STCN75 Temperature Sensor has a dedicated open drain overlimit signal/interrupt
(OS
/INT) output which features a thermal alarm function. This function provides a userprogrammable trip and turn-off temperature. It can operate in either of two selectable
modes:
● Section 2.3: Comparator mode
● Section 2.4: Interrupt mode.
At power-up the STCN75 immediately begins measuring the temperature and converting
the temperature to a digital value.
The measured temperature value is compared with a temperature limit (which is stored in
the 16-bit (T
the 16-bit (T
OS
/INT pin is activated (see Figure 3 on page 8).
Note: See Pin descriptions on page 8 for details.
Figure 1. Logic diagram
) READ/WRITE register), and the hysteresis temperature (which is stored in
OS
) READ/WRITE register). If the measured value exceeds these limits, the
HYS
V
DD
SDA
(1)
OS/INT
SCL
A
0
A
1
A
2
STCN75
GND
1. SDA and OS/INT are open drain.
Table 1. Signal names
Pin Sym Type/direction Description
1SDA
(1)
Input/output Serial data input/output
2 SCL Input Serial clock input
3OS/INT
(1)
Output Overlimit signal/interrupt alert output
4 GND Supply ground Ground
5A
6A
7A
8V
1. SDA and OS/INT are open drain.
2
1
0
DD
Input Address2 input
Input Address1 input
Input Address0 input
Supply power Supply voltage (2.7 V to 5.5 V)
(1)
AI11899
Doc ID 13307 Rev 9 7/36
Description STCN75
Figure 2. Connections
(1)
SDA
SCL
OS/INT
(1)
GND
1. SDA and OS/INT are open drain.
Figure 3. Functional block diagram
Temperature
Sensor and
Analog-to-Digital
Converter (ADC)
S-D
V
DD
A
0
A
1
Configuration Register
Temperature Register
THYS Set Point Register
TOS Set Point Register
2-wire I2C Interface
8
1
2
3
4
V
DD
7
A
0
6
A
1
5
A
2
Pointer Register
Control and Logic
Comparator
AI11841
OS/INT
SDA
A
2
1.3 Pin descriptions
See Figure 1 on page 7 and Table 1 on page 7 for a brief overview of the signals
connected to this device.
1.3.1 SDA (open drain)
This is the serial data input/output pin for the 2-wire serial communication port.
1.3.2 SCL
This is the serial clock input pin for the 2-wire serial communication port.
1.3.3 OS/INT (open drain)
This is the overlimit signal/interrupt alert output pin. It is open drain, so it needs a pull-up
resistor. In Interrupt mode, it outputs a pulse whenever the measured temperature exceeds
the programmed threshold (T
the measured temperature is above or below the threshold and hysteresis (T
SCL
GND
). It behaves as a thermostat, toggling to indicate whether
OS
HYS
).
AI11833a
8/36 Doc ID 13307 Rev 9
STCN75 Description
1.3.4 GND
Ground; it is the reference for the power supply. It must be connected to system ground.
1.3.5 A2, A1, A0
A2, A1, and A0 are selectable address pins for the 3 LSBs of the I2C interface address.
They can be set to V
or GND to provide 8 unique address selections.
DD
1.3.6 V
DD
This is the supply voltage pin, and ranges from +2.7 V to +5.5 V.
Doc ID 13307 Rev 9 9/36
Operation STCN75
2 Operation
After each temperature measurement and analog-to-digital conversion, the STCN75 stores
the temperature as a 16-bit two’s complement number (see Table 5: Register pointers
selection summary on page 16) in the 2-byte temperature register (see Table 7 on page 17).
The most significant bit (S) indicates if the temperature is positive or negative:
● for positive numbers S = 0, and
● for negative numbers S = 1.
The most recently converted digital measurement can be read from the temperature register
at any time. Since temperature conversions are performed in the background, reading the
temperature register does not affect the operation in progress.
The temperature data is provided by the 9 MSBs (bits 15 through 7). Bits 6 through 0 are
unused. Table 3 on page 14 gives examples of the digital output data and corresponding
temperatures. The data is compared to the values in the T
the OS
/INT is updated based on the result of the comparison and the operating mode.
The alarm fault tolerance is controlled by the FT1 and FT0 bits in the configuration register.
They are used to set up a fault queue. This prevents false tripping of the OS
the STCN75 is used in a noisy environment (see Table 2 on page 13).
OS
and T
registers, and then
HYS
/INT pin when
The active state of the OS
/INT output can be changed via the polarity bit (POL) in the
configuration register. The power-up default is active-low.
If the user does not wish to use the thermostat capabilities of the STCN75, the
OS
/INToutput should be left floating.
Note: If the thermostat is not used, the T
system data.
OS
and T
registers can be used for general storage of
HYS
10/36 Doc ID 13307 Rev 9
STCN75 Operation
2.1 Applications information
STCN75 digital temperature sensors are optimal for thermal management and thermal
protection applications. They require no external components for operations except for pullup resistors on SCL, SDA, and OS
recommended. The sensing device of STCN75 is the chip itself. The typical interface
connection for this type of digital sensor is shown in Figure 4 on page 11.
Intended applications include:
● System thermal management
● Computers/disk drivers
● Electronics/test equipment
● Power supply modules
● Consumer products
● Battery management
● Fax/printers management
● Automotive
Figure 4. Typical 2-wire interface connections diagram
/INT outputs. A 0.1 µF bypass capacitor on VDD is
Pull-up
V
DD
10kΩ
1. SDA and OS/INT are open drain.
STCN75
O.S./INT
A
0
A
1
A
2
(1)
SDA
2.2 Thermal alarm function
The STCN75 thermal alarm function provides user-programmable thermostat capability and
allows the STCN75 to function as a standalone thermostat without using the serial interface.
The OS
this pin is configured with active-low polarity by default.
/INT output is the alarm output. This signal is an open drain output, and at power-up,
V
DD
SCL
(1)
GND
0.1µF
V
DD
Pull-up
V
DD
10kΩ 10kΩ
I2C Address = 1001000 (1001A2A1A0)
Master
Device
AI12200
Doc ID 13307 Rev 9 11/36
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