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 SO8 2 ■ 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.
Contents STLM75 Contents 1 2 3 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.1 Serial communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 Temperature sensor output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3 Pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 SDA (open drain) . . . . . . . . .
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 . . . . . . . . . . . .
List of tables STLM75 List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. Table 11. Table 12. Table 13. Table 14. Table 15. Table 16. Table 17. Table 18. Table 19. 4/40 Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Fault tolerance setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
STLM75 List of figures List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Figure 15. Figure 16. Figure 17. Figure 18. Figure 19. Figure 20. Figure 21. Figure 22. Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Connections (SO8 and MSOP8/TSSOP8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Description 1 STLM75 Description The STLM75 is a high-precision digital CMOS temperature sensor IC with a sigma-delta temperature-to-digital 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 and SO8 packages.
STLM75 1.2 Description 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.
Description STLM75 Table 1. Signal names Pin Sym Type/direction 1 SDA(1) Input/output 2 SCL Input (1) Description Serial data input/output Serial clock input Output Overlimit signal/interrupt alert output 3 OS/INT 4 GND Supply ground 5 A2 Input Address2 input 6 A1 Input Address1 input 7 A0 Input Address0 input 8 VDD Supply power Ground Supply voltage (2.7 V to 5.5 V) 1. SDA and OS/INT are open drain. Figure 2.
STLM75 1.3 Description 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.
Operation 2 STLM75 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.
STLM75 2.1 Operation 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/INT outputs. A 0.1 µF bypass capacitor on VDD is 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.
Operation 2.2 STLM75 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.
STLM75 2.4 Operation Interrupt mode In interrupt mode, the OS output first becomes active when the measured temperature exceeds the TOS value a consecutive number of times as determined by the FT value in the configuration register. Once activated, the OS can only be cleared by either putting the STLM75 into shutdown mode or by reading from any register (temperature, configuration, TOS, or THYS) on the device.
Operation 2.5 STLM75 Fault tolerance For both comparator and interrupt modes, the alarm “fault tolerance” setting plays a role in determining when the OS output will be activated. Fault tolerance refers to the number of consecutive times an error condition must be detected before the user is notified. Higher fault tolerance settings can help eliminate false alarms caused by noise in the system. The alarm fault tolerance is controlled by the bits (4 and 3) in the configuration register.
STLM75 2.7 Operation Temperature data format Table 3 shows the relationship between the output digital data and the external temperature. Temperature data for the temperature, TOS, and THYS registers is represented as a 9-bit, two’s complement word. The left-most bit in the output data stream contains temperature polarity information for each conversion. If the sign bit is '0', the temperature is positive and if the sign bit is '1,' the temperature is negative. Table 3.
Functional description 3 STLM75 Functional description The STLM75 registers have unique pointer designations which are defined in Table 5 on page 17. Whenever any READ/WRITE operation to the STLM75 register is desired, the user must “point” to the device register to be accessed.
STLM75 Functional description Table 5. Register pointers selection summary Pointer value (H) P1 P0 Name Description 00 0 0 TEMP Temperature register 16 01 0 1 CONF Configuration register 02 1 0 THYS 03 1 1 TOS 3.1.
Functional description 3.1.3 STLM75 Temperature register The temperature register is a two-byte (16-bit) “Read only” register (see Table 7 on page 18). Digital temperatures from the T-to-D converter are stored in the temperature register in two’s complement format, and the contents of this register are updated each time the T-to-D conversion is finished. The user can read data from the temperature register at any time.
STLM75 3.1.5 Functional description Hysteresis temperature register (THYS) THYS register is a two-byte (16-bit) READ/WRITE register that stores the userprogrammable lower trip-point temperature for the thermal alarm in two’s complement format (see Table 8). This register defaults to 75 °C at power-up (i.e., 0100 1011 0000 0000). The format of this register is the same as that of the temperature register.
Functional description 3.3 STLM75 Serial interface Writing to and reading from the STLM75 registers is accomplished via the two-wire serial interface protocol which requires that one device on the bus initiates and controls all READ and WRITE operations. This device is called the “master” device. The master device also generates the SCL signal which provides the clock signal for all other devices on the bus. These other devices on the bus are called “slave” devices.
STLM75 3.4.4 Functional description Data valid The state of the data line represents valid data when after a start condition, the data line is stable for the duration of the high period of the clock signal. The data on the line may be changed during the low period of the clock signal. There is one clock pulse per bit of data. Each data transfer is initiated with a start condition and terminated with a stop condition.
Functional description 3.4.5 STLM75 Acknowledge Each byte of eight bits is followed by one acknowledge bit. This acknowledge bit is a low level put on the bus by the receiver whereas the master generates an extra acknowledge related clock pulse (see Figure 7). A slave receiver which is addressed is obliged to generate an acknowledge after the reception of each byte that has been clocked out of the slave transmitter.
STLM75 3.5 Functional description READ mode In this mode the master reads the STLM75 slave after setting the slave address (see Figure 8). Following the WRITE mode control bit (R/W=0) and the acknowledge bit, the word address 'An' is written to the on-chip address pointer. There are two READ modes: Preset pointer locations (e.g.
Functional description Figure 9. STLM75 Typical 2-byte READ from preset pointer location (e.g. temp - TOS, THYS) 1 9 1 0 0 Start by Master 1 1 A2 A1 A0 R/W 9 1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 Most Significant Data Byte Address Byte 9 Stop Cond. by No ACK Master by Master Least Significant Data Byte ACK by STLM75 ACK by Master AI12227 Figure 10. Typical pointer set followed by an immediate READ for 2-byte register (e.g.
STLM75 3.6 Functional description WRITE mode In this mode the master transmitter transmits to the STLM75 slave receiver. Bus protocol is shown in Figure 12. Following the START condition and slave address, a logic '0' (R/W = 0) is placed on the bus and indicates to the addressed device that word address will follow and is to be written to the on-chip address pointer. These modes are shown in the WRITE mode typical timing diagrams (see Figure 12, and Figure 13, and Figure 14). Figure 12.
Functional description STLM75 Figure 14. TOS and THYS WRITE 1 9 1 0 Start by Master 0 1 1 A2 A1 A0 R/W 9 0 0 0 0 0 0 Pointer Byte Address Byte ACK by STLM75 ACK by STLM75 1 9 D7 D6 D5 D4 D3 D2 D1 D0 1 9 D7 D6 D5 D4 D3 D2 D1 D0 Most Significant Data Byte Least Significant Data Byte ACK by STLM75 26/40 D1 D0 Doc ID 13296 Rev 12 ACK by STLM75 Stop Cond.
STLM75 Typical operating characteristics Figure 15. Temperature variation vs. voltage 140 120 100 Temperature (°C) 4 Typical operating characteristics 80 –20 60 0.
Maximum ratings 5 STLM75 Maximum ratings Stressing the device above the ratings listed in the absolute maximum ratings table may cause permanent damage to the device. These are stress ratings only and operation of the device at these or any other conditions above those indicated in the operating sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 10.
STLM75 6 DC and AC parameters DC and AC parameters This section summarizes the operating measurement conditions, and the DC and AC characteristics of the device. The parameters in the DC and AC characteristics tables that follow, are derived from tests performed under the measurement conditions summarized in Table 11. Designers should check that the operating conditions in their circuit match the operating conditions when relying on the quoted parameters. Table 11.
DC and AC parameters Table 12. Sym VDD IDD IDD1 STLM75 DC and AC characteristics Description Supply voltage Test condition(1) Min TA = –55 to +125 °C 2.7 Typ(2) Max Unit 5.5 V VDD supply current, active temperature conversions VDD = 3.3 V 125 150 µA VDD supply current, communication only TA = 25 °C 70 100 µA Shutdown mode supply current, serial port inactive TA = 25 °C 1.0 µA Accuracy for corresponding range 2.7 V ≤ VDD ≤ 5.5 V Resolution –25 °C < TA < 100 ±0.5 ±2.
STLM75 DC and AC parameters Figure 16. Bus timing requirements sequence SDA tBUF tHD:STA tHD:STA tF tR SCL tHIGH P S tLOW tSU:DAT tHD:DAT tSU:STA tSU:STO SR P AI00589 Table 13. AC characteristics Parameter(1)(2) Sym fSCL SCL clock frequency tBUF Time the bus must be free before a new transmission can start tF tHD:DAT(3) Min Max Unit 0 400 kHz 1.
Package mechanical data 7 STLM75 Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark.
STLM75 Package mechanical data Figure 17. SO8 – 8-lead plastic small outline package mechanical drawing h x 45˚ A2 A c ccc b e 0.25 mm GAUGE PLANE D k 8 E1 E 1 A1 L L1 SO-A Note: Drawing is not to scale. Table 14. SO8 – 8-lead plastic small outline package mechanical data mm inches Sym Typ Min A Max Typ Min 1.75 Max 0.069 A1 0.10 A2 1.25 b 0.28 0.48 0.011 0.019 c 0.17 0.23 0.007 0.009 ccc 0.25 0.004 0.010 0.049 0.10 0.004 D 4.90 4.80 5.00 0.193 0.189 0.
Package mechanical data STLM75 Figure 18. MSOP8 (TSSOP8) – 8-lead, thin shrink small outline (3 mm x 3 mm) package mechanical drawing D 8 5 c E1 1 E 4 k A1 A L2 L1 ccc b Note: L A2 e E3_ME Drawing is not to scale. Table 15. MSOP8 (TSSOP8) – 8-lead, thin shrink small outline (3 mm x 3 mm) package mechanical data mm inches Sym Typ Min A 0.00 0.15 0.75 0.95 b 0.22 c A2 Typ Min 1.10 A1 0.85 Max 0.043 0.000 0.006 0.030 0.037 0.40 0.009 0.016 0.08 0.23 0.003 0.
STLM75 Package mechanical data Figure 19. Carrier tape for SO8 and MSOP8 (TSSOP8) packages P0 E P2 D T A0 F TOP COVER TAPE W B0 P1 CENTER LINES OF CAVITY K0 USER DIRECTION OF FEED AM03073v1 Table 16. Carrier tape dimensions for SO8 and MSOP8 (TSSOP8) packages Package W D SO8 12.00 ±0.30 1.50 +0.10/ –0.00 MSOP8 12.00 (TSSOP8) ±0.30 1.50 +0.10/ –0.00 E P0 P2 F B0 K0 P1 T 1.75 4.00 2.00 5.50 ±0.10 ±0.10 ±0.10 ±0.05 6.50 ±0.10 5.30 ±0.10 2.20 ±0.10 8.00 ±0.10 0.30 ±0.
Package mechanical data STLM75 Figure 20. Reel schematic T 40mm min. Access hole At slot location B D C N A G measured Tape slot In core for Full radius At hub Tape start 2.5mm min.width AM04928v1 Table 17. Reel dimensions for 12 mm carrier tape - SO8 and MSOP8 (TSSOP8) packages A B (max) (min) SO8 330 mm (13-inch) 1.5 mm MSOP8 (TSSOP8) 180 mm (7-inch) 1.5 mm Package Note: 36/40 D N (min) (min) 13 mm ± 0.2 mm 20.2 mm 60 mm 12.4 mm + 2/–0 mm 18.4 mm 13 mm ± 0.2 mm 20.
STLM75 8 Part numbering Part numbering Table 18. Ordering information scheme Example: STLM75 M 2 F Device type STLM75 Package M = SO8 DS = MSOP8 (TSSOP8) Temperature range 2 = –55 to 125 °C Shipping method F = ECOPACK® package, tape & reel E = ECOPACK® package, tube For other options, or for more information on any aspect of this device, please contact the ST sales office nearest you.
Package marking information 9 STLM75 Package marking information Figure 21. Device topside marking information (SO8) STLM75M2 xxxxx(1) AM04934v1 1. Traceability codes Figure 22. Device topside marking information (MSOP8/TSSOP8) LM75 xxxx(1) AM04935v1 1.
STLM75 10 Revision history Revision history Table 19. Document revision history Date Revision Changes 23-Dec-2005 1 Initial release.
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