STCN75 Digital temperature sensor and thermal watchdog Datasheet − production data 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 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 STCN75 Contents 1 2 3 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.1 Serial communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 Temperature sensor output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3 Pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 SDA (open drain) . . . . . . . . .
STCN75 Contents 3.4.4 Data valid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.4.5 Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.5 READ mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.6 WRITE mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4 Typical operating characteristics .
List of tables STCN75 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. 4/36 Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Fault tolerance setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
STCN75 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. Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Description 1 STCN75 Description The STCN75 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 package.
STCN75 1.2 Description Temperature sensor output The STCN75 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: ● Section 2.3: Comparator mode ● Section 2.4: Interrupt mode. At power-up the STCN75 immediately begins measuring the temperature and converting the temperature to a digital value.
Description STCN75 Figure 2. Connections SDA(1) SCL OS/INT(1) GND 1 2 3 4 8 7 6 5 VDD A0 A1 A2 AI11841 1. SDA and OS/INT are open drain. Figure 3. Functional block diagram Temperature Sensor and Analog-to-Digital Converter (ADC) S-D 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 1.
STCN75 1.3.4 Description 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.
Operation 2 STCN75 Operation After each temperature measurement and analog-to-digital conversion, the STCN75 stores the temperature as a 16-bit two’s complement number (see Table 5: Register pointers selection summary on page 16) in the 2-byte temperature register (see Table 7 on page 17). The most significant bit (S) indicates if the temperature is positive or negative: ● for positive numbers S = 0, and ● for negative numbers S = 1.
STCN75 2.1 Operation Applications information STCN75 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 STCN75 is the chip itself. The typical interface connection for this type of digital sensor is shown in Figure 4 on page 11.
Operation 2.3 STCN75 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 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 asserted.
STCN75 2.5 Operation 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 (4 and 3) in the configuration register.
Operation 2.7 STCN75 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.
STCN75 3 Functional description Functional description The STCN75 registers have unique pointer designations which are defined in Table 5 on page 16. Whenever any READ/WRITE operation to the STCN75 register is desired, the user must “point” to the device register to be accessed. All of these user-accessible registers can be accessed via the digital serial interface at anytime (see Section 3.
Functional description Table 5. STCN75 Register pointers selection summary Pointer P1 P0 value (H) Name Width (bits) Description Type Power-on (R/W) default Comments 00 0 0 TEMP Temperature register 16 Readonly N/A 01 0 1 CONF Configuration register 8 R/W 00 02 1 0 THYS Hysteresis register 16 R/W 4B00 Default = 75 °C 03 1 1 TOS Overtemperature shutdown 16 R/W 5000 Set point for overtemperature shutdown (TOS) limit default = 80 °C 3.1.
STCN75 3.1.3 Functional description Temperature register The temperature register is a two-byte (16-bit) “Read only” register (see Table 7). 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.
Functional description 3.1.5 STCN75 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.
STCN75 3.3 Functional description Serial interface Writing to and reading from the STCN75 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.
Functional description 3.4.4 STCN75 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.
STCN75 Functional description Figure 6. Acknowledgement sequence CLOCK PULSE FOR ACKNOWLEDGEMENT START SCL FROM MASTER 1 DATA OUTPUT BY TRANSMITTER 2 8 MSB 9 LSB DATA OUTPUT BY RECEIVER AI00601 3.5 READ mode In this mode the master reads the STCN75 slave after setting the slave address (see Figure 7). 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 8. STCN75 Typical 2-byte READ from preset pointer location (e.g. temp - TOS, THYS) 1 9 0 1 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 Least Significant Data Byte ACK by STCN75 ACK by Master Stop Cond. by No ACK Master by Master AI12227 Figure 9. Typical pointer set followed by an immediate READ for 2-byte register (e.g.
STCN75 3.6 Functional description WRITE mode In this mode the master transmitter transmits to the STCN75 slave receiver. Bus protocol is shown in Figure 11. 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 11, and Figure 12, and Figure 13 on page 24). Figure 11.
Functional description STCN75 Figure 13. TOS and THYS WRITE 1 9 0 1 Start by Master 0 1 1 A2 A1 A0 R/W 9 0 0 0 0 0 D1 D0 Pointer Byte Address Byte ACK by STCN75 ACK by STCN75 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 STCN75 24/36 0 Doc ID 13307 Rev 9 ACK by STCN75 Stop Cond.
STCN75 Typical operating characteristics Figure 14. Temperature variation vs. voltage 140 120 100 Temperature (°C) 4 Typical operating characteristics 80 –20 60 0.
Maximum ratings 5 STCN75 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.
STCN75 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, Operating and AC measurement conditions. Designers should check that the operating conditions in their circuit match the operating conditions when relying on the quoted parameters.
DC and AC parameters Table 12. Sym VDD IDD IDD1 STCN75 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 –25 °C < TA < 100 ±0.5 ±2.
STCN75 DC and AC parameters Figure 15. Bus timing requirements sequence SDA tBUF tHD:STA tHD:STA tR tF SCL tHIGH P S tLOW tSU:DAT tHD:DAT SR tSU:STA P tSU:STO 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 Min Max Unit 0 400 kHz 1.
Package mechanical data 7 STCN75 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.
STCN75 Package mechanical data Figure 16. 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 1. Drawing is not to scale. Table 14. 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 STCN75 Figure 17. 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 15. Package Carrier tape dimensions for MSOP8 (TSSOP8) package W MSOP8 12.00 (TSSOP8) ±0.30 32/36 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.
STCN75 Package mechanical data Figure 18. Reel schematic T 40mm min. Access hole At slot location B D C N A Tape slot In core for Full radius Tape start 2.5mm min.width G measured At hub AM04928v1 Table 16. Reel dimensions for 12 mm carrier tape - MSOP8 (TSSOP8) package A B (max) (min) 330 mm (13 inch) 1.5 mm C 13 mm ± 0.2 mm D N (min) (min) 20.2 mm 60 mm Doc ID 13307 Rev 9 G 12.4 mm + 2 / –0 mm T (max) 18.
Part numbering 8 STCN75 Part numbering Table 17. Ordering information scheme Example: STCN75 DS 2 F Device type STCN75 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.
STCN75 9 Revision history Revision history Table 18. Revision history Date Revision Changes 25-Jul-2006 1 Initial release 17-Nov-2006 2 Changed document to new template; document status updated from target specification to preliminary data; updated footnotes in Table 1: Signal names; updated footnotes, VOL1, VIL, VOL2 and IOL in Table 12: DC and AC characteristics; deleted tTIME-OUT from Table 13: AC characteristics; updated package mechanical data for the SO8N package in Section 7.
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