ST STLM75 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

– Supports bus time-out feature
– Selectable bus address allows connection

■ 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)

2

C/SMBus-compatible serial interface

of up to eight devices on the bus

STLM75

SO8

MSOP8

(TSSOP8)

August 2010 Doc ID 13296 Rev 12 1/40

www.st.com

1

Contents STLM75

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

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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

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

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

3.1.5 Hysteresis temperature register (T

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

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

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

OS

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

HYS

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

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

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

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STLM75 Contents

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

Doc ID 13296 Rev 12 3/40

List of tables STLM75

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

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

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

and T

OS

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

register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

HYS

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STLM75 List of figures

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

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

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

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

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

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

, T

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

HYS

OS

and T

OS

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

HYS

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

Doc ID 13296 Rev 12 5/40

Description STLM75

1 Description

The STLM75 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 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 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 STLM75 registers to
customize operation of the device.

6/40 Doc ID 13296 Rev 12

STLM75 Description

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 user­programmable 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
the 16-bit (T
OS

/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

) 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. SDA and OS/INT are open drain.

SCL

A
A
A

(1)

0
1
2

STLM75

GND

OS/INT

(1)

AI11899

Doc ID 13296 Rev 12 7/40

Description STLM75

Table 1. Signal names

Pin Sym Type/direction Description

1SDA

(1)

Input/output Serial data input/output

2 SCL Input Serial clock input

(1)

3OS

/INT

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)

Figure 2. Connections (SO8 and MSOP8/TSSOP8)

(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)

Σ-Δ

V

DD

A

0

A

1

Configuration Register

Temperature Register

THYS Set Point Register

TOS Set Point Register

2-wire I2C Interface

1
2
3
4

8

V

DD

7

A

0

6

A

1

5

A

2

Pointer Register

Control and Logic

Comparator

AI11841

OS/INT

SDA

A

2

8/40 Doc ID 13296 Rev 12

GND

SCL

AI11833a

STLM75 Description

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

1.3.4 GND

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

OS

HYS

).

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

1.3.6 V

DD

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

or GND to provide 8 unique address selections.

DD

Doc ID 13296 Rev 12 9/40

Operation STLM75

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

OS

and T

registers, and then

HYS

/INT pin when

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
should be left floating.

Note: If the thermostat is not used, the T

system data.

OS

and T

output

registers can be used for general storage of

HYS

10/40 Doc ID 13296 Rev 12

STLM75 Operation

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 pull­up resistors on SCL, SDA, and OS
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

/INT outputs. A 0.1 µF bypass capacitor on VDD is

Pull-up

V

DD

10kΩ

1. SDA and OS/INT are open drain.

STLM75

O.S./INT

A

0

A

1

A

2

(1)

SDA

V

DD

SCL

(1)

GND

0.1μF

V

DD

Pull-up

V

DD

10kΩ 10kΩ

I2C Address = 1001000 (1001A2A1A0)

Master

Device

AI12200

Doc ID 13296 Rev 12 11/40

Operation STLM75

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
tolerance number of consecutive temperature measurements are greater than the value
stored in the T

register, the OS output will be asserted.

OS

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

OS

output is active, it will remain active until the first time the measured temperature drops
below the temperature stored in the T

When the thermostat is in comparator mode, the OS
any amount of hysteresis. The OS
exceeds the T

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

OS

output becomes active when the measured temperature

HYS

register.

can be programmed to operate with

tolerance (FT) bits in the configuration register. The OS
temperature falls below the value stored in T

register for a consecutive number of times

HYS

as defined by the fault tolerance bits (FT1 and FT0). Putting the device into shutdown mode
does not clear OS

in comparator mode.

OS

and T

registers. If a fault

HYS

then becomes inactive when the

12/40 Doc ID 13296 Rev 12