ST STDS75 User Manual

STDS75

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 I2C/SMBus-compatible serial interface

–Selectable serial bus address allows connection of up to eight devices on the same bus

■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

■Pinand software-compatible with DS75 (dropin 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

Datasheet − production data

MSOP8

(TSSOP8)

March 2012

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This is information on a product in full production.

www.st.com

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/INT (open drain) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.3.4 GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.3.5 A2, A1, A0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.3.6 VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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

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 (TOS) . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.1.5 Hysteresis temperature register (THYS) . . . . . . . . . . . . . . . . . . . . . . . . . 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
3.4.3	Stop data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	20

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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

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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. TOS and THYS register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 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

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

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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 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 - TOS, THYS) . . . . . . . . . . . .	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.	TOS and THYS WRITE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	26
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
	mechanical drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	33
Figure 18.	Carrier tape for MSOP8 (TSSOP8) package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	34
Figure 19.	Reel schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	35

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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 I2C-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 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.

1.1Serial 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.

In addition, the serial interface gives the user easy access to all STDS75 registers to customize operation of the device.

1.2Temperature 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.

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STDS75	Description

The measured temperature value is compared with a temperature limit (which is stored in the 16-bit (TOS) READ/WRITE register), and the hysteresis temperature (which is stored in the 16-bit (THYS) READ/WRITE register). If the measured value exceeds these limits, the

OS/INT pin is activated (see Figure 3 on page 8).

Figure 1.

Logic diagram

VDD

SDA(1)

A0

SCL

STDS75

A1

A2

O.S./INT(1)

GND

AI11840

1. SDA and

OS/INT are open drain.

Note:

See Pin descriptions on page 9 for details.

Table 1.

Signal names

Pin

Symbol/name

Type/direction

Description

1

SDA(1)

Input/ output

Serial data input/output

2

SCL

Input

Serial clock input

3

OS/INT(1)

Output

Overlimit signal/interrupt alert output

4

GND

Supply ground

Ground

5

A2

Input

Address2 input

6

A1

Input

Address1 input

7

A0

Input

Address0 input

8

VDD

Supply power

Supply voltage (2.7 V to 5.5 V)

1. SDA and OS/INT are open drain.

Note:

See Pin descriptions on page 9 for details.

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Description	STDS75

Figure 2. Connections

SDA(1) 1 8 VDD

SCL	2	7	A0
O.S./INT(1)	3	6	A1
GND	4	5	A2

AI11841

1. SDA and OS/INT are open drain.

Note:

See Pin descriptions on page 9 for details.

Figure 3. Functional block diagram

Temperature	Configuration Register	Pointer Register
Sensor and
Analog-to-Digital	Temperature Register
Converter (ADC)
Σ-	THYS Set Point Register
VDD	TOS Set Point Register	Control and Logic
			O.S.
		Comparator
A0			SDA
A1	2-wire I2C Interface
A2			SCL
		GND	AI11833a

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STDS75	Description

1.3Pin descriptions

See Figure 1 on page 7 and Table 1 on page 7 for a brief overview of the signals connected to this device.

1.3.1SDA (open drain)

This is the serial data input/output pin for the 2-wire serial communication port.

1.3.2SCL

This is the serial clock input pin for the 2-wire serial communication port.

1.3.3OS/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 VDD or GND to provide 8 unique address selections.
1.3.6	VDD
	This is the supply voltage pin, and ranges from +2.7 V to +5.5 V.

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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 TOS and THYS
	registers, and then the
				OS/INT is updated based on the result of the comparison and the
	operating mode. The number of TOS and THYS bits used during the thermostat comparison
	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 TOS and THYS will be
	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).
	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/INT
	output should be left floating.
Note:	If the thermostat is not used, the TOS and THYS registers can be used for general storage of
	system data.

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STDS75	Operation

2.1Applications 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/INT outputs. A 0.1 µF bypass capacitor is recommended. 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

Pull-up		VDD	Pull-up
VDD			VDD
	VDD	10kΩ	10kΩ
10kΩ	STDS75	0.1μF
O.S./INT(1) SCL			Master
			Device
A0	SDA(1)
A1	GND		I2C Address = 1001000 (1001A2A1A0)
A2

AI11832

1. SDA and OS/INT are open drain.

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Operation	STDS75

2.2Thermal 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.

2.3Comparator 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 TOS and THYS registers. If a fault tolerance number of consecutive temperature measurements are greater than the value stored in the TOS register, the OS/INT output will be activated.

For example, if the FT1 and FT0 bits are equal to “10” (fault tolerance = 4), four consecutive temperature measurements must exceed TOS to activate the OS/INT output. Once the

OS/INT output is active, it will remain active until the first time the measured temperature drops below the temperature stored in the THYS register.

When the thermostat is in comparator mode, the OS/INT can be programmed to operate with any amount of hysteresis. The OS/INT output becomes active when the measured temperature exceeds the TOS value a consecutive number of times as defined by the FT1

and FT0 fault tolerance (FT) bits in the configuration register. The OS/INT then stays active until the first time the temperature falls below the value stored in THYS. Putting the device

into shutdown mode does not clear OS/INT in comparator mode.

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