ST STDS75 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 serial bus address allows

■ Thermometer resolution is user-configurable

from 9 (default) to 12 bits (0.5 °C to 0.0625 °C)

■ 9-bit conversion time is 150 ms (max)

■ Programmable temperature threshold and

hysteresis set points

■ Wide power supply range - operating voltage

range: 2.7 V to 5.5 V

■ Pin- and software-compatible with DS75 (drop-

in replacement)

■ Power-up defaults permit standalone operation

as thermostat

■ Shutdown mode to minimize power

consumption

■ Separate open drain output pin operates as an

interrupt or comparator/thermostat output (dual
purpose event pin)

■ MSOP8 (TSSOP8) package

2

C/SMBus-compatible serial interface

connection of up to eight devices on the
same bus

STDS75

Datasheet − production data

MSOP8

(TSSOP8)

March 2012 Doc ID 13297 Rev 9 1/38

This is information on a product in full production.

www.st.com

1

Contents STDS75

Contents

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

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

1.2 Temperature sensor output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

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

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

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

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

OS

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

HYS

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

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

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

2/38 Doc ID 13297 Rev 9

STDS75 Contents

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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Doc ID 13297 Rev 9 3/38

List of tables STDS75

List of tables

Table 1. Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

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

Table 7. Programmable resolution configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 8. Temperature register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Table 9. T

Table 10. STDS75 serial bus slave addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 11. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 12. Operating and AC measurement conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 13. DC and AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table 14. AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

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

Table 16. Carrier tape dimensions for MSOP8 (TSSOP8) package. . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table 17. Reel dimensions for 12 mm carrier tape - MSOP8 (TSSOP8) package . . . . . . . . . . . . . . . 35

Table 18. Ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Table 19. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

and T

OS

mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

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

HYS

4/38 Doc ID 13297 Rev 9

STDS75 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 connection 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. MSOP8 (TSSOP8) – 8-lead, thin shrink small outline (3 mm x 3 mm) package

Figure 18. Carrier tape for MSOP8 (TSSOP8) package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Figure 19. Reel schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

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

, T

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

HYS

OS

and T

OS

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

HYS

mechanical drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Doc ID 13297 Rev 9 5/38

Description STDS75

1 Description

The STDS75 is a high-precision CMOS (digital) temperature sensor IC with a delta-sigma
analog-to-digital (ADC) 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 programmable 9- to 12-bit ADC
which monitor and digitize the temperature to a resolution up to 0.0625 °C. The STDS75 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. At power-up, the
STDS75 defaults to 9-bit resolution for software compatibility with the STLM75.

The STDS75 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 delta-sigma analog-to-digital converter (ADC) converts the measured
temperature to a digital value that is calibrated in °C; for Fahrenheit applications a lookup
table or conversion routine is required.

The STDS75 is factory-calibrated and requires no external components to measure
temperature.

1.1 Serial communications

The STDS75 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 400kHz. 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 STDS75 registers to
customize operation of the device.

1.2 Temperature sensor output

The STDS75 temperature sensor has a dedicated open drain overlimit signal/alert
(OS

/INT/Alert) 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 STDS75 comes up in 9-bit mode and immediately begins measuring the
temperature and converting the temperature to a digital value. The resolution of the digital
output data is user-configurable to 9, 10, 11, or 12 bits which correspond to temperature
increments of 0.5 °C, 0.25 °C, 0.125 °C, and 0.0625 °C, respectively.

6/38 Doc ID 13297 Rev 9

STDS75 Description

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).

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

OS

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

HYS

Figure 1. Logic diagram

V

DD

(1)

SDA

SCL

O.S./INT

1. SDA and OS/INT are open drain.

(1)

Note: See Pin descriptions on page 9 for details.

Table 1. Signal names

Pin Symbol/name Type/direction Description

1SDA

(1)

2 SCL Input Serial clock input

3OS/INT

(1)

4 GND Supply ground Ground

5A2Input Address2 input

6A

7A

8V

1. SDA and OS/INT are open drain.

1

0

DD

Input/ output Serial data input/output

Output Overlimit signal/interrupt alert output

Input Address1 input

Input Address0 input

Supply power Supply voltage (2.7 V to 5.5 V)

STDS75

GND

A

0

A

1

A

2

AI11840

Note: See Pin descriptions on page 9 for details.

Doc ID 13297 Rev 9 7/38

Description STDS75

Figure 2. Connections

(1)

SDA

SCL

O.S./INT

(1)

GND

1. SDA and OS/INT are open drain.

Note: See Pin descriptions on page 9 for details.

Figure 3. Functional block diagram

Temperature

Sensor and
Analog-to-Digital
Converter (ADC)

Σ-Δ

V

DD

A

0

Configuration Register

Temperature Register

THYS Set Point Register

TOS Set Point Register

1
2
3
4

8

V

DD

7

A

0

6

A

1

5

A

2

Pointer Register

Control and Logic

Comparator

AI11841

O.S.

SDA

A

1

A

2

2-wire I2C Interface

GND

SCL

AI11833a

8/38 Doc ID 13297 Rev 9

STDS75 Description

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.

Note: The open drain thermostat output that indicates if the temperature has exceeded user-

programmable limits (over/under temperature indicator).

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

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 13297 Rev 9 9/38

Operation STDS75

2 Operation

After each temperature measurement and analog-to-digital conversion, the STDS75 stores
the temperature as a 16-bit two’s complement number in the 2-byte temperature register
(see Table 8: Temperature register format). The most significant bit (S, bit 15) 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.

Bits 3 through 0 of the temperature register are hardwired to logic '0.' When the STDS75 is
configured for 12-bit resolution, the 12 MSBs (bits 15 through 4) of the temperature register
will contain temperature data. For 11-bit resolution, the 11 MSBs (bits 15 through 5) of the
temperature register will contain data, and bit 4 will read out as logic '0.' For 10-bit
resolution, the 10 MSBs (bits 15 through 6) will contain data, and for 9-bit resolution the
9 MSBs (bits 15 through 7) will contain data and all unused LSBs will contain '0's.

Table 3 on page 15 gives examples of 12-bit resolution digital output data and the

corresponding temperatures. The data is compared to the values in the T
registers, and then the OS
operating mode. The number of T

/INT is updated based on the result of the comparison and the

OS

and T

bits used during the thermostat comparison

HYS

is equal to the conversion resolution set by the FT1 and FT0 bits in the configuration
register. For example, if the resolution is 9 bits, only the 9 MSBs of T

OS

used by the thermostat comparator. The alarm fault tolerance is controlled by the FTI and
FTO 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 STDS75 is used in a noisy environment (see

Table 2 on page 14).

OS

and T

and T

HYS

HYS

will be

The active state of the OS

/INT output can be changed via the polarity (POL) bit in the

configuration register. The power-up default is active-low.

If the user does not wish to use the thermostat capabilities of the STDS75, the OS
output should be left floating.

Note: If the thermostat is not used, the T

OS

and T

HYS

system data.

10/38 Doc ID 13297 Rev 9

/INT

registers can be used for general storage of

STDS75 Operation

2.1 Applications information

STDS75 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
The sensing device of STDS75 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 connection diagram

/INT outputs. A 0.1 µF bypass capacitor is recommended.

Pull-up

V

DD

10kΩ

1. SDA and OS/INT are open drain.

STDS75

O.S./INT

A

0

A

1

A

2

(1)

SDA

GND

V

DD

SCL

(1)

0.1μF

V

DD

Pull-up

V

10kΩ 10kΩ

I2C Address = 1001000 (1001A2A1A0)

DD

Master
Device

AI11832

Doc ID 13297 Rev 9 11/38

Operation STDS75

2.2 Thermal alarm function

The STDS75 thermal alarm function provides user-programmable thermostat capability and
allows the STDS75 to function as a standalone thermostat without using the serial interface.
The OS

/INT 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) temperature conversion
occurs, the new digital temperature is compared to the value stored in the T
registers. If a fault tolerance number of consecutive temperature measurements are greater
than the value stored in the T

register, the OS/INT output will be activated.

OS

For example, if the FT1 and FT0 bits are equal to “10” (fault tolerance = 4), four consecutive
temperature measurements must exceed T
OS

/INT 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
with any amount of hysteresis. The OS
temperature exceeds the T

value a consecutive number of times as defined by the FT1

OS

/INT output becomes active when the measured

and FT0 fault tolerance (FT) bits in the configuration register. The OS
until the first time the temperature falls below the value stored in T
into shutdown mode does not clear OS

to activate the OS/INT output. Once the

OS

register.

HYS

/INT can be programmed to operate

/INT then stays active

. Putting the device

HYS

/INT in comparator mode.

OS

and T

HYS

12/38 Doc ID 13297 Rev 9