STDS75 Digital temperature sensor and thermal watchdog Datasheet − production data Features ■ Measures temperatures from –55 °C to +125 °C (–67 °F to +257 °F) – ±0.
Contents STDS75 Contents 1 2 3 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.1 Serial communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 Temperature sensor output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3 Pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 SDA (open drain) . . . . . . . . .
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 .
List of tables STDS75 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. 4/38 Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Fault tolerance setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
STDS75 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. Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Description 1 STDS75 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.
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 O.S./INT(1) A1 A2 GND AI11840 1. SDA and OS/INT are open drain. Note: See Pin descriptions on page 9 for details.
Description STDS75 Figure 2. Connections SDA(1) SCL O.S./INT(1) GND 1 2 3 4 8 7 6 5 VDD A0 A1 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 Sensor and Analog-to-Digital Converter (ADC) Σ-Δ Pointer Register Configuration Register Temperature Register THYS Set Point Register VDD Control and Logic Comparator TOS Set Point Register SDA A0 A1 2-wire I2C Interface A2 SCL GND 8/38 O.S.
STDS75 1.3 Description 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.
Operation 2 STDS75 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.
STDS75 2.1 Operation 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/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.
Operation 2.2 STDS75 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.
STDS75 2.4 Operation Interrupt mode In Interrupt mode, the OS/INT output first becomes active when the measured temperature exceeds the TOS value a consecutive number of times equal to the FT value in the configuration register. Once activated, the OS/INT can only be cleared by either putting the STDS75 into shutdown mode or by reading from any register (temperature, configuration, TOS, or THYS) on the device.
Operation 2.5 STDS75 Fault tolerance For both comparator and interrupt modes, the alarm “fault tolerance” setting plays a role in determining when the OS/INT 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 (bits 4 and 3) in the configuration register.
STDS75 2.7 Operation Temperature data format Table 3 shows the relationship between the output digital data and the external temperature for 12-bit resolution. Temperature data for temperature, TOS and THYS registers is represented by 9-bit, 10-bit, 11-bit, and 12-bit depending upon the resolution bits RC1, RC0 (bits 6 and 5) in the configuration register (see Table 7 on page 17). The default resolution is 9-bits.
Functional description 3 STDS75 Functional description The STDS75 registers have unique pointer designations which are defined in Table 5 on page 16. Whenever any READ/WRITE operation to the STDS75 register is desired, the user must “point” to the device register to be accessed.
STDS75 3.1.2 Functional description Configuration register The configuration register is used to store the device settings such as device operation mode, OS/INT operation mode, OS/INT polarity, and OS/INT fault queue. The configuration register allows the user to program various options such as conversion resolution (see Table 7), thermostat fault tolerance, thermostat polarity, thermostat operating mode, and shutdown mode.
Functional description 3.1.3 STDS75 Temperature register The temperature register is a two-byte (16-bit) “Read only” register (see Table 8 on page 18). Digital temperatures from the ADC are stored in the temperature register in two’s complement format, and the contents of this register are updated each time the A/D conversion is finished. The user can read data from the temperature register at any time.
STDS75 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 9). 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. The 4 LSBs of the THYS register are hardwired to zero, so data written to these bits is ignored.
Functional description 3.3 STDS75 Serial interface Writing to and reading from the STDS75 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.
STDS75 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 STDS75 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.
STDS75 3.5 Functional description READ mode In this mode the master reads the STDS75 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. STDS75 Typical 2-byte READ from preset pointer location (e.g. temp - TOS, THYS) 1 9 1 0 0 Start by Master 1 A2 A1 A0 1 R 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 Least Significant Data Byte ACK by STDS75 ACK by Master Stop Cond. by No ACK Master by Master AI12281b Figure 10. Typical pointer set followed by an immediate READ for 2-byte register (e.g.
STDS75 3.6 Functional description WRITE mode In this mode the master transmitter transmits to the STDS75 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 on page 26). Figure 12.
Functional description STDS75 Figure 14. TOS and THYS WRITE 1 9 1 0 Start by Master 0 1 A2 A1 A0 1 W 9 0 0 0 0 0 0 Pointer Byte Address Byte ACK by STDS75 ACK by STDS75 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 STDS75 26/38 D1 D0 Doc ID 13297 Rev 9 ACK by STDS75 Stop Cond.
STDS75 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 STDS75 Maximum ratings Stressing the device above the rating 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 11.
STDS75 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 12. Designers should check that the operating conditions in their circuit match the operating conditions when relying on the quoted parameters. Table 12.
DC and AC parameters Table 13. Sym VDD IDD IDD1 STDS75 DC and AC characteristics Description Supply voltage Test condition(1) Min TA = –55 to +125 °C 2.7 Typ(2) 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 Standby 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 °C ±0.5 ±2.
STDS75 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 14. 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 STDS75 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.
STDS75 Package mechanical data Figure 17. 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 L L2 A2 L1 ccc b e E3_ME Note: 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 Max Min 1.10 A1 0.00 0.15 0.75 0.95 b 0.22 c A2 Typ 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.
Package mechanical data STDS75 Figure 18. Carrier tape for MSOP8 (TSSOP8) package 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. Package Carrier tape dimensions for MSOP8 (TSSOP8) package W MSOP8 12.00 (TSSOP8) ±0.30 34/38 D 1.50 +0.10/ –0.00 E P0 P2 F 1.75 4.00 2.00 5.50 ±0.10 ±0.10 ±0.10 ±0.05 A0 B0 K0 P1 T 5.30 ±0.10 3.40 ±0.10 1.40 ±0.10 8.00 ±0.10 0.30 ±0.
STDS75 Package mechanical data Figure 19. Reel schematic T 40mm min. Access hole At slot location B D C N A G measured Tape slot In core for Full radius Tape start 2.5mm min.width At hub AM04928v1 Table 17. Reel dimensions for 12 mm carrier tape - MSOP8 (TSSOP8) package A B (max) (min) 330 mm (13-inch) 1.5 mm Note: C 13 mm ± 0.2 mm D N (min) (min) 20.2 mm 60 mm G 12.4 mm + 2/–0 mm T (max) 18.
Part numbering 8 STDS75 Part numbering Table 18. Ordering information scheme Example: STDS75 DS 2 F Device type STDS75 Package M = SO8(1) DS = MSOP8 (TSSOP8) Temperature range 2 = –55 to 125 °C Shipping method F = ECOPACK® package, tape & reel E = ECOPACK® package, tube(2) 1. Not recommended for new design, contact local ST sales office for availability. Refer to the STTS75M2F replacement part. 2. Not recommended for new design, contact local ST sales office for availability.
STDS75 9 Revision history Revision history Table 19. Document revision history Date Revision Changes 28-Nov-2005 1 Initial release. 08-May-06 2 Update characteristics, diagrams (Figure 3, 4, 9, 10, 11, 12, 13, 14, 15; Table 1, 2, 6, 9, 12, 13, 14) 22-Jan-2007 3 Updates to parameters, package mechanical information (Figure 17, Table 15) and part numbering (Table 18).
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