ST STLM75 User Manual

August 2010 Doc ID 13296 Rev 12 1/40

STLM75

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

C/SMBus-compatible serial interface

– Supports bus time-out feature

– Selectable bus address allows connection

of up to eight devices on the bus

■ Wide power supply range-operating voltage

range: 2.7 V to 5.5 V

■ Conversion time is 150 ms (max)

■ Programmable temperature threshold and

hysteresis set points

■ Pin- and software-compatible with LM75 (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)

■ Packages:

–SO8

– MSOP8 (TSSOP8)

SO8

MSOP8

(TSSOP8)

www.st.com

Contents STLM75

2/40 Doc ID 13296 Rev 12

Contents

1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.1 Serial communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.2 Temperature sensor output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.3 Pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.3.1 SDA (open drain) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.3.2 SCL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.3.3 OS

/INT (open drain) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.3.4 GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.3.5 A2, A1, A0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.3.6 V

DD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.1 Applications information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.2 Thermal alarm function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.3 Comparator mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.4 Interrupt mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.5 Fault tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.6 Shutdown mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.7 Temperature data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.8 Bus timeout feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.1 Registers and register set formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.1.1 Command/pointer register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.1.2 Configuration register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.1.3 Temperature register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.1.4 Overlimit temperature register (T

) . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.1.5 Hysteresis temperature register (T

HYS

) . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.2 Power-up default conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.3 Serial interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.4 2-wire bus characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.4.1 Bus not busy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.4.2 Start data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

STLM75 Contents

Doc ID 13296 Rev 12 3/40

3.4.3 Stop data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.4.4 Data valid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.4.5 Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.5 READ mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.6 WRITE mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4 Typical operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

5 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

6 DC and AC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

8 Part numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

9 Package marking information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

List of tables STLM75

4/40 Doc ID 13296 Rev 12

List of tables

Table 1. Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Table 2. Fault tolerance setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Table 3. Relationship between temperature and digital output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Table 4. Command/pointer register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Table 5. Register pointers selection summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 6. Configuration register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 7. Temperature register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Table 8. T

and T

HYS

Table 9. STLM75 serial bus slave addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 10. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 11. Operating and AC measurement conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 12. DC and AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table 13. AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table 14. SO8 – 8-lead plastic small outline package mechanical data. . . . . . . . . . . . . . . . . . . . . . . 33

Table 15. MSOP8 (TSSOP8) – 8-lead, thin shrink small outline (3 mm x 3 mm) package

mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table 16. Carrier tape dimensions for SO8 and MSOP8 (TSSOP8) packages . . . . . . . . . . . . . . . . . 35

Table 17. Reel dimensions for 12 mm carrier tape - SO8 and MSOP8 (TSSOP8) packages . . . . . . 36

Table 18. Ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Table 19. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

STLM75 List of figures

Doc ID 13296 Rev 12 5/40

List of figures

Figure 1. Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 2. Connections (SO8 and MSOP8/TSSOP8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 3. Functional block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 4. Typical 2-wire interface connections diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 5. OS

output temperature response diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 6. Serial bus data transfer sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 7. Acknowledgement sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 8. Slave address location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 9. Typical 2-byte READ from preset pointer location (e.g. temp - T

, T

HYS

) . . . . . . . . . . . . 24

Figure 10. Typical pointer set followed by an immediate READ for 2-byte register (e.g. temp). . . . . . 24

Figure 11. Typical 1-byte READ from the configuration register with preset pointer . . . . . . . . . . . . . . 24

Figure 12. Typical pointer set followed by an immediate READ from the configuration register . . . . . 25

Figure 13. Configuration register WRITE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 14. T

and T

HYS

WRITE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 15. Temperature variation vs. voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 16. Bus timing requirements sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Figure 17. SO8 – 8-lead plastic small outline package mechanical drawing . . . . . . . . . . . . . . . . . . . . 33

Figure 18. MSOP8 (TSSOP8) – 8-lead, thin shrink small outline (3 mm x 3 mm) package

mechanical drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Figure 19. Carrier tape for SO8 and MSOP8 (TSSOP8) packages . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Figure 20. Reel schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 21. Device topside marking information (SO8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 22. Device topside marking information (MSOP8/TSSOP8). . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Description STLM75

6/40 Doc ID 13296 Rev 12

1 Description

The STLM75 is a high-precision digital CMOS temperature sensor IC with a sigma-delta

temperature-to-digital converter and an I

C-compatible serial digital interface. It is targeted

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 and SO8 packages.

The device contains a band gap temperature sensor and 9-bit ADC which monitor and

digitize the temperature to a resolution up to 0.5 °C. The STLM75 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 STLM75 is pin-for-pin and software

compatible with the LM75B.

The STLM75 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 on-board 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 STLM75 is factory-calibrated and requires no external components to measure

temperature.

1.1 Serial communications

The STLM75 has a simple 2-wire I

C-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.

In addition, the serial interface gives the user easy access to all STLM75 registers to

customize operation of the device.

STLM75 Description

Doc ID 13296 Rev 12 7/40

1.2 Temperature sensor output

The STLM75 temperature sensor has a dedicated open drain overlimit signal/interrupt

(OS

/INT) output which features a thermal alarm function. This function provides a user-

programmable trip and turn-off temperature. It can operate in either of two selectable

modes:

● Comparator mode, and

● Interrupt mode.

At power-up the STLM75 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

) READ/WRITE register), and the hysteresis temperature (which is stored in

the 16-bit (T

HYS

) READ/WRITE register). If the measured value exceeds these limits, the

/INT pin is activated (see Figure 3 on page 8 and Table 2 on page 14).

Note: See Pin descriptions on page 9 for details.

Figure 1. Logic diagram

1. SDA and OS/INT are open drain.

AI11899

SDA

(1)

STLM75

GND

SCL

OS/INT

(1)

Description STLM75

8/40 Doc ID 13296 Rev 12

Figure 2. Connections (SO8 and MSOP8/TSSOP8)

1. SDA and OS/INT are open drain.

Figure 3. Functional block diagram

Table 1. Signal names

Pin Sym Type/direction Description

1SDA

(1)

1. SDA and OS/INT are open drain.

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

Input Address2 input

Input Address1 input

Input Address0 input

Supply power Supply voltage (2.7 V to 5.5 V)

GND

SCL

SDA

(1)

OS/INT

(1)

AI11841

AI11833a

Temperature

Sensor and

Analog-to-Digital

Converter (ADC)

Σ-Δ

GND

Configuration Register

SDA

SCL

OS/INT

2-wire I

C Interface

Pointer Register

Control and Logic

Comparator

Temperature Register

THYS Set Point Register

TOS Set Point Register

STLM75 Description

Doc ID 13296 Rev 12 9/40

1.3 Pin descriptions

See Figure 1 on page 7 and Table 1 on page 8 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

). It behaves as a thermostat, toggling to indicate whether

the measured temperature is above or below the threshold and hysteresis (T

HYS

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 I

C interface address.

They can be set to V

or GND to provide 8 unique address selections.

1.3.6 V

This is the supply voltage pin, and ranges from +2.7 V to +5.5 V.

Operation STLM75

10/40 Doc ID 13296 Rev 12

2 Operation

After each temperature measurement and analog-to-digital conversion, the STLM75 stores

the temperature as a 16-bit two’s complement number (see Table 5: Register pointers

selection summary on page 17) in the 2-byte temperature register (see Table 7 on page 18).

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 15 gives examples of the digital output data and corresponding

temperatures. The data is compared to the values in the T

and T

HYS

registers, and then

the OS

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

/INT pin when

the STLM75 is used in a noisy environment (see Table 3 on page 15).

The active state of the OS

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 STLM75, the OS

output

should be left floating.

Note: If the thermostat is not used, the T

and T

HYS

registers can be used for general storage of

system data.

STLM75 Operation

Doc ID 13296 Rev 12 11/40

2.1 Applications information

STLM75 digital temperature sensors are optimal for thermal management and thermal

protection applications. They require no external components for operations except for pull-

up resistors on SCL, SDA, and OS

/INT outputs. A 0.1 µF bypass capacitor on V

recommended. The sensing device of STLM75 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

1. SDA and OS/INT are open drain.

AI12200

Pull-up

O.S./INT

(1)

Master

Device

0.1μF

STLM75

SCL

GND

SDA

(1)

Pull-up

10kΩ

10kΩ 10kΩ

C Address = 1001000 (1001A

)

Operation STLM75

12/40 Doc ID 13296 Rev 12

2.2 Thermal alarm function

The STLM75 thermal alarm function provides user-programmable thermostat capability and

allows the STLM75 to function as a standalone thermostat without using the serial interface.

The OS

output is the alarm output. This signal is an open drain output, and at power-up, this

pin is configured with active-low polarity by default.

2.3 Comparator mode

In comparator mode, each time a temperature-to-digital (T-to-D) conversion occurs, the new

digital temperature is compared to the value stored in the T

and T

HYS

registers. If a fault

tolerance number of consecutive temperature measurements are greater than the value

stored in the T

For example, if the FT1 and FT0 bits are equal to “10” (fault tolerance = 4), four consecutive

temperature measurements must exceed T

to activate the OS output. Once the OS

output is active, it will remain active until the first time the measured temperature drops

below the temperature stored in the T

HYS

When the thermostat is in comparator mode, the OS

can be programmed to operate with

any amount of hysteresis. The OS

output becomes active when the measured temperature

exceeds the T

value a consecutive number of times as defined by the FT1 and FT0 fault

tolerance (FT) bits in the configuration register. The OS

then becomes inactive when the

temperature falls below the value stored in T

HYS

as defined by the fault tolerance bits (FT1 and FT0). Putting the device into shutdown mode

does not clear OS

in comparator mode.

+ 28 hidden pages