NCT75 Industry Standard Digital Temperature Sensor with 2‐wire Interface The NCT75 is a two-wire serially programmable temperature sensor with an over-temperature/interrupt output pin to signal out of limit conditions. This is an open-drain pin and can operate in either comparator or interrupt mode. Temperature measurements are converted into digital form using a high resolution (12 bit), sigma-delta, analog-to-digital converter (ADC). The device operates over the –55C to +125C temperature range. Communication with the NCT75 is accomplished via the SMBus/I2C interface. Three address selection pins, A2, A1 and A0, can be used to connect up to 8 NCT75s to a single bus. Through this interface the NCT75s internal registers may be accessed. These registers allow the user to read the current temperature, change the configuration settings and adjust the temperature limits. The NCT75 has a wide supply voltage range of 3.0 V to 5.5 V. The average supply current is 575 mA at 3.3 V. It also offers a shutdown mode to conserve power. The typical shutdown current is 3 mA. The NCT75 is available in three, space saving packages – 8-lead DFN, 8-lead Micro8t and 8-lead SOIC and is also fully pin and register compatible with the LM75 and TCN75. DFN8 CASE 506AA SOIC8 CASE 751 PIN ASSIGNMENT SDA 1 8 VDD SCL 2 (Top View) OS/ALERT 3 7 A0 6 A1 5 A2 GND 4 MARKING DIAGRAMS 1 12-bit Temperature-to-Digital Converter Input Voltage Range from 3.0 V to 5.5 V Temperature Range from −55C to +125C SMBus/I2C Interface Overtemperature Indicator Support for SMBus/ALERT Shutdown Mode for Low Power Consumption One-shot Mode Available in 8-pin DFN, 8-pin Micro8t and SOIC Packages These Devices are Pb-Free, Halogen Free/BFR Free and are RoHS Compliant XXXX AYWG G XXMG G 1 DFN8 Micro8t XXXX M A Y W G = Specific Device Code = Date Code = Assembly Location = Year = Work Week = Pb-Free Package (Note: Microdot may be in either location) 8 Applications Micro8t CASE 846A 8 Features http://onsemi.com Computer Thermal Monitoring Thermal Protection Isolated Sensors Battery Management Office Electronics Electronic Test Equipment Thermostat Controls System Thermal Management 1 XXXXX ALYWX G SOIC8 XXXXX A L Y W G = Specific Device Code = Assembly Location = Wafer Lot = Year = Work Week = Pb-Free Package ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page 11 of this data sheet. Semiconductor Components Industries, LLC, 2012 August, 2012 − Rev. 3 1 Publication Order Number: NCT75/D NCT75 VDD 8 SDA SCL A2 A1 A0 1 2 5 REGISTERS TWO-WIRE INTERFACE 6 7 CONFIGURATION THYST TEMPERATURE TOS 3 ONE-SHOT OS/ALERT DELTA-SIGMA ADC CONTROL LOGIC GND 4 Figure 1. Simplified Block Diagram VDD 3.0 V To 5.5 V CBYPASS A2 ADDRESS (SET AS DESIRED) A1 A0 5 6 1 7 NCT75 OS/ALERT 2 SDA SCL SERIAL INTERFACE 3 4 NOTE: SDA, SCL AND OS/ALERT PINS REQUIRE PULL-UP RESISTORS TO VDD GND Figure 2. Typical Application Circuit Table 1. PIN FUNCTION DESCRIPTION Pin No. Pin Name 1 SDA SMBus/I2C Serial Bi-directional Data Input/Output. Open-drain pin; needs a pull-up resistor. Description 2 SCL Serial Clock Input. Open-drain pin; needs a pull-up resistor. 3 OS/ALERT 4 GND 5 A2 SMBus/I2C Serial Bus Address Selection Pin. Connect to GND or VDD to set the desired I2C address. 6 A1 SMBus/I2C Serial Bus Address Selection Pin. Connect to GND or VDD to set the desired I2C address. 7 A0 SMBus/I2C Serial Bus Address Selection Pin. Connect to GND or VDD to set the desired I2C address. 8 VDD Over-temperature Indicator. Open-drain output; needs a pullup resistor. Active Low output. Power Supply Ground. Positive Supply Voltage, 3.0 V to 5.5 V. Bypass to ground with a 0.1 mF bypass capacitor. http://onsemi.com 2 NCT75 Table 2. ABSOLUTE MAXIMUM RATINGS (Note 1) Symbol Rating Supply Voltage VDD Input Voltage on SCL, SDA, A2, A1, A0 and OS/ALERT. Input Current on SDA, A2, A1, A0 and OS/ALERT. Value Unit −0.3 to +7 V −0.3 to VDD + 0.3 V IIN −1 to +50 mA TJ(max) 150.7 C Operating Temperature Range TOP −55 to 125 C Storage Temperature Range TSTG −65 to 160 C ESD Capability, Human Body Model (Note 2) ESDHBM 2,000 V ESD Capability, Machine Model (Note 2) ESDMM 400 V Maximum Junction Temperature Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. 1. Refer to ELECTRICAL CHARACTERISTICS and APPLICATION INFORMATION for Safe Operating Area. 2. This device series incorporates ESD protection and is tested by the following methods: ESD Human Body Model tested per AEC−Q100−002 (EIA/JESD22−A114) ESD Machine Model tested per AEC−Q100−003 (EIA/JESD22−A115) Table 3. OPERATING RANGES (Note 3) Symbol Min Max Unit Operating Supply Voltage VIN 3.0 5.5 V Operating Ambient Temperature Range TA −55 125 C Rating 3. Refer to ELECTRICAL CHARACTERISTICS and APPLICATION INFORMATION for Safe Operating Area. Table 4. SMBus TIMING SPECIFICATIONS Parameter Symbol Serial Clock Frequency Test Conditions fSCL Start Condition Hold Time tHD:STA Stop Condition Setup Time tSU:STO 90% of SCL to 10% of SDA Min Typ Max Unit DC − 400 kHz 0.6 − − ms 100 − − ns Clock Low Period tLOW 1.3 − − ms Clock High Period tHIGH 0.6 − − ms Start Condition Setup Time tSU:STA 90% of SCL to 90% of SDA 100 − − ns Data Setup Time tSU:DAT 10% of SDA to 10% of SCL 100 − − ns Data Hold Time (Note 4) tHD:DAT 10% of SCL to 10% of SDA 0 − 76 ns SDA/SCL Rise Time tR − 300 − ns SDA/SCL Fall Time tF − 300 − ns Minimum RESET Pulse Width tRESET 1.3 − − ms Bus Free Time Between STOP and START Conditions tBUF 1.3 − − ms 4. This refers to the hold time when the NCT75 is writing data to the bus. tR tF tHD;STA tLOW SCL tHD;STA tHD;DAT tHIGH tSU;STA tSU;DAT tSU;STO SDA tBUF STOP START START Figure 3. Serial Interface Timing http://onsemi.com 3 STOP NCT75 Table 5. ELECTRICAL CHARACTERISTICS (TA = TMIN to TMAX, VDD = 3.0 V to 5.5 V. All specifications for −55C to +125C, unless otherwise noted.) Test Conditions Parameter Min Typ Max Unit − − − − − − 1 2 3 C TEMPERATURE SENSOR AND ADC Accuracy at VDD = 3.0 V to 5.5 V TA = 0C to +70C TA = −25C to +100C TA = −55C to +125C ADC Resolution − 12 − Bits Temperature Resolution − 0.0625 − C − 48.5 − ms − 80 − ms Supply Voltage 3.0 − 5.5 V POR Threshold 2.75 − − V − − 0.8 mA Temperature Conversion Time One-shot Mode Update Rate POWER REQUIREMENTS I2 C Supply Current Peak Current while Converting and Interface Inactive Average Current Average Current over 1 Conversion Cycle − 0.44 0.575 mA Shutdown Mode at 3.3 V Supply Current in Shutdown Mode − 3 12 mA IOL = 4 mA − 0.15 0.4 V OS/ALERT OUTPUT (OPEN DRAIN) Output Low Voltage, VOL Pin Capacitance − 10 − pF OS/ALERT Pin Pulled Up to 5.5 V − 0.1 5 mA Input Current VIN = 0 V to VDD − − 1 mA Input Low Voltage, VIL VDD = 3.3 V (Note 5) − − 0.3 x VDD V Input High Voltage, VIH VDD = 3.3 V (Note 5) 0.7xVDD − − V SCL, SDA Glitch Rejection Input Filtering Suppresses Noise Spikes of Less than 50 ns − − 50 ns − 3 − pF High Output Leakage Current, IOH DIGITAL INPUTS (SDA, SCL) Pin Capacitance DIGITAL OUTPUT (SDA) (OPEN DRAIN) Output High Current, IOH VOH = 5 V − − 1 mA Output Low Voltage, VOL IOL = 3 mA − − 0.4 V − 3 − pF Output Capacitance, COUT 5. Guaranteed by characterization, not production tested. http://onsemi.com 4 NCT75 APPLICATION INFORMATION Functional Description While the ADC of the NCT75 can theoretically measure temperatures in the range of −128C to 127C, the NCT75 is guaranteed to measure from −55C to +125C. Table 6 shows the relevant temperature bits for a 12 bit temperature reading. A 2-byte read is required to obtain the full 12 bit temperature reading. If an 8 bit (1C resolution) reading is required then a single byte read is sufficient. The NCT75 temperature sensor converts an analog temperature measurement to a digital representation by using an on-chip measurement transistor and a 12 bit Delta-Sigma ADC. The device includes an open drain ALERT output which can be used to signal that the programmed temperature limit has been exceeded. The two main modes of operation are normal and shutdown mode. In normal mode the NCT75 performs a new temperature conversion every 80 ms. This new value is then updated to the temperature value register (address 0x00) and also compared to the TOS register limit (default = 80C). If the temperature value register is read during the conversion sequence the value returned is the previously stored value. A bus read does not affect the conversion that is in progress. In shutdown mode temperature conversion is disabled and the temperature value register holds the last valid temperature reading. The NCT75 can still be communicated with in this mode as the interface is still active. The device mode is controlled via bit 0 of the configuration register. While in shutdown mode a conversion can be initiated by writing an arbitrary value to the one-shot register (0x04). This has the effect of powering up the NCT75, performing a conversion, comparing the new temperature with the programmed limit and then going back into shutdown mode. The OS/ALERT pin can be configured in many ways to allow it to be used in many different system configurations. The overtemperature output can be configured to operate as a comparator type output (which is self clearing once the temperature has returned below the hysteresis value) or an interrupt type output (which requires the master to read an internal register AND the temperature to return below the hysteresis value before going into an inactive state). The ALERT pin can also be configured as an active high or active low output. Table 6. 12-BIT TEMPERATURE DATA FORMAT Temperature Binary Value D15 to D4 Hex Value −55C 1100 1001 0000 0xC90 −25C 1110 0111 0000 0xE70 −0.0625C 1111 1111 1111 0xFFF 0C 0000 0000 0000 0x000 +0.0625C 0000 0000 0001 0x001 +25C 0001 1001 0000 0x190 +75.25C 0100 1011 0100 0x4B4 +100C 0110 0100 0000 0x640 +125C 0111 1101 0000 0x7D0 Temperature Data Conversion 12-bit Temperature Data Format Positive Temperature = ADC Code (decimal)/16 Example 190h = 400d/16 = +25C Negative Temperature = (ADC Code(decimal) − 4096)/16 Example E70h = (3696d – 4096)/16 = −25C One-shot Mode One of the features of the NCT75 is a One-shot Temperature Measurement Mode. This mode is useful if reduced power consumption is a design requirement. To enable one-shot mode bit 5 of the configuration register needs to be set. Once, enabled, the NCT75 goes immediately into shutdown mode. Here, the current consumption is reduced to a typical value of 3 mA. Writing address 0x04 to the address pointer register initiates a one-shot temperature measurement. This powers up the NCT75, carries out a temperature measurement, and then powers down again. The data written to this register is irrelevant and is not stored. It is the write operation that causes the one-shot conversion. Temperature Measurement Results The results of the on chip temperature measurements are stored in the temperature value register and compared with the TOS and THYST limit register. The temperature value, TOS and THYST registers are 16 bits wide and have a resolution of 0.0625C. The data is stored as a 12 bit 2s complement word. The data is left justified, D15 is the MSB and is the sign bit. The four LSBs (D3 to D0) are always 0 as they are not part of the result. http://onsemi.com 5 NCT75 Registers The NCT75 contains six registers for configuring and reading the teperature: the address pointer register, 4 data registers and a one-shot register. The configuration register, the address pointer register and the one-shot register are all 8 bits wide while the temperature register, THYST and TOS registers are all 16 bits wide. All registers, except for the temperature register, can be be read from and written to (the temperature register is read only). The power on state and address of each register are listed in Table 9. 82C 81C 80C TOS Temperature 79C 78C 77C 76C 75C THYST 74C Address Pointer Register The address pointer register is used to select which register is to respond to a read or write operation. The three LSBs (P2, P1 & P0) of this write only register are used to select the appropriate register. On power up this register is loaded with a value of 0x00 and so points to the temperature register. Table 7 shows the bits of the address pointer register and Table 8 shows the pointer address selecting each of the registers available. 73C 72C OS/ALERT PIN (COMPARATOR MODE) POLARITY = 0 OS/ALERT PIN (INTERRUPT MODE) POLARITY = 0 Table 7. ADDRESS POINTER REGISTER OS/ALERT PIN (COMPARATOR MODE) POLARITY = 1 Default OS/ALERT PIN (INTERRUPT MODE) POLARITY = 1 P7 P6 P5 P4 P3 P2 P1 P0 0 0 0 0 0 0 0 0 Read Read Read Table 8. REGISTER ADDRESSES SELECTION Figure 4. One-shot OS/ALERT Pin Operation Fault Queue A fault is defined as when the temperature exceeds a pre-defined temperature limit. This limit can be programmed in the THYST and the TOS setpoint registers. Bits 3 and 4 of the configuration register determine the number of faults necessary to trigger the OS/ALERT pin. Up to six faults can be programmed to prevent false tripping when the NCT75 is used in a noisy temperature environment. In order for the OS/ALERT output to be set these faults must occur consecutively. P2 P1 P0 Register Selected 0 0 0 Stored Temperature 0 0 1 Configuration 0 1 0 THYST Setpoint 0 1 1 TOS Setpoint 1 0 0 One-shot Table 9. NCT75 REGISTER SET Register Name Hex 5C 0x00 (R) Stored Temperature Value 0x0000 0 0x00 − 0x01 (R/W) Configuration 0x02 (R/W) THYST 0x4B00 75 0x03 (R/W) TOS 0x5000 80 0x04 (R/W) One-shot 0xXX − http://onsemi.com 6 Power-on Default Value Register Address NCT75 Temperature Register The temperature measured by the parts internal sensor is stored in this 16-bit read only register. The data is stored in twos complement format with the MSB as the sign bit. The 8 MSBs must be read frist followed by the 8 LSBs. Table 10. TEMPERATURE VALUE REGISTER MSB LSB D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 0 0 0 0 0 0 0 0 0 X X X X Configuration Register D[4:3]: Fault Queue D4 D3 These two bits determine how many overtemperature conditions occur before the OS/Alert pin is triggered. This helps to prevent false triggering of the output. 0 0 = 1 Fault (Default) 0 1 = 2 Faults 1 0 = 4 Faults 2 1 = 6 Faults This 8-bit read/write register is used to configure the NCT75 into its various modes of operation. The different modes are listed in Table 11 and explained in more detail below. Table 11. CONFIGURATION REGISTER Bit Configuration Default Value D7 Reserved 0 D6 Reserved 0 D5 One-shot Mode 0 D4 Fault-queue 0 D3 Fault-queue 0 D2 OS/ALERT Pin Polarity 0 D1 Cmp/Int Mode 0 D0 Shutdown Mode 0 D2: OS/Alert pin polarity This selects the polarity of the OS/Alert output pin. D2 = 0 Output is active low. (Default) D2 = 1 Output is active high. D1: Cmp/Int D1 = 0 Comparator mode. (Default) D1 = 1 Interrupt mode. D0: Shutdown D0 = 0 Normal mode – part is fully powered. (Default) D0 = 1 Shutdown mode – all circuitry except for the SMBus interface is powered down. Write a 0 to this bit to power up again. D7: Reserved Write 0 to this bit. D6: Reserved Write 0 to this bit. D5: One-shot Mode D5 = 0 Part is in normal mode and converting every 60 ms. (Default) D5 = 1 Setting this bit puts the part into one-shot mode. The part is normally powered down in this mode until the one shot register is written to. Once this register is written to one conversion is performed and the part returns to its shutdown state. THYST Register The THYST register stores the temperature hysteresis value for the overtemperature output. This value is picked to stop the OS/Alert pin from being asserted and de-asserted in noisy temperature environments. This limit is stored in the 16 bit register in twos complement format. The MSB is the temperature sign bit. The 8 MSBs must be read first followed by the 8 LSBs. The default value is +75C. Table 12. THYST REGISTER MSB LSB D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 1 0 0 1 0 1 1 0 0 0 0 X X X X TOS Register This register stores the temperature limit at which the part asserts an OS/Alert. Once the measured temperature reaches this value an alert or overtemperature output is generated. The data is stored in twos complement format with the MSB as the sign bit. The 8 MSBs must be read frist followed by the 8 LSBs. The default limit +80C. Table 13. TOS REGISTER MSB LSB D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 1 0 1 0 0 0 0 0 0 0 0 X X X X http://onsemi.com 7 NCT75 Serial Interface Control of the NCT75 is carried out via the SMBus/I2C compatible serial interface. The NCT75 is connected to this bus as a slave device, under the control of a master device. master writes to the slave device. If the R/W bit is a one then the master reads from the slave device. 2. Data is sent over the serial bus in sequences of nine clock pulses, eight bits of data followed by an acknowledge bit from the receiver of data. Transitions on the data line must occur during the low period of the clock signal and remain stable during the high period, since a low-to-high transition when the clock is high can be interpreted as a stop signal. 3. When all data bytes have been read or written, stop conditions are established. In write mode, the master pulls the data line high during the tenth clock pulse to assert a stop condition. In read mode, the master overrides the acknowledge bit by pulling the data line high during the low period before the ninth clock pulse. This is known as no acknowledge. The master takes the data line low during the low period before the tenth clock pulse, then high during the tenth clock pulse to assert a stop condition. Serial Bus Address Control of the NCT75 is carried out via the serial bus. The NCT75 is connected to this bus as a slave device under the control of a master device. The NCT75 has a 7-bit serial address. The four MSBs are fixed and set to 1001 while the 3 LSBs can be configured by the user using pins 5, 6 and 7 (A2, A1 and A0). Each of these pins can be configured in one of two ways low or high. This gives eight different address options listed in Table 14 below. The state of these pins is continually sampled and so can be changed after power up. Table 14. SERIAL BUS ADDRESS OPTIONS MSBs LSBs Address A6 A5 A4 A3 A2 A1 A0 Hex 1 0 0 1 0 0 0 0x48 1 0 0 1 0 0 1 0x49 1 0 0 1 0 1 0 0x4A 1 0 0 1 0 1 1 0x4B 1 0 0 1 1 0 0 0x4C 1 0 0 1 1 0 1 0x4D 1 0 0 1 1 1 0 0x4E 1 0 0 1 1 1 1 0x4F Any number of bytes of data can be transferred over the serial bus in one operation. However, it is not possible to mix read and write in one operation because the type of operation is determined at the beginning and cannot subsequently be changed without starting a new operation. Writing Data There are two types of writes used in the NCT75: The NCT75 also features a SMBus/I2C timeout function whereby the SMBus/I2C interface times out after 22.5 ms of no activity on the SDA line. After this time, the NCT75 resets the SDA line back to its idle state (high impedance) and waits for the next start condition. The serial bus protocol operates as follows: 1. The master initiates data transfer by establishing a start condition, defined as a high to low transition on the serial data line SDA, while the serial clock line SCL remains high. This indicates that an address/data stream is going to follow. All slave peripherals connected to the serial bus respond to the start condition and shift in the next eight bits, consisting of a 7-bit address (MSB first) plus a read/write (R/W) bit, which deternimes the direction of the data transfer i.e. whether data is written to, or read from, the slave device. The peripheral with the address corresponding to the transmitted address responds by pulling the data line low during the low period before the ninth clock pulse, known as the acknowledge bit. All other devices on the bus now remain idle while the selected device waits for data to be read from or written to it. If the R/W bit is a zero then the Setting up the Address Pointer Register for a Register Read To read data from a particular register, the address pointer register must hold the address of the register being read. To configure the address pointer register a single write operation (shown in Figure 5). It consists of the device address followed by the address being written to the address pointer register. This will then be followed by a read operation. Writing Data to a Register Due to the different size registers used by the NCT75, there are two types of write operations. One is for the 8 bit wide configuration register and the other for the 16 bit wide limit registers. Figure 6 shows the sequence required to write to the configuration register. It consists of the device address, the data register being written to and the data being written the selected register. The two temperature limit registers (THYST and TOS) are 16 bits wide and require two data bytes to be written to these registers. This sequence is shown in Figure 7. It consists of the device address, the data register being written to and the two data byes being written to the selected register. http://onsemi.com 8 NCT75 1 9 1 9 SCL SDA A6 A5 START BY MASTER A4 A3 A2 A1 R/W A0 D7 D6 ACK. BY NCT75 FRAME 1 SERIAL BUS ADDRESS BYTE D5 D4 D3 D2 D1 D0 ACK. BY NCT75 FRAME 2 ADDRESS POINTER REGISTER BYTE STOP BY MASTER Figure 5. Writing to the Address Pointer Register 1 9 1 9 SCL SDA A6 A5 START BY MASTER A4 A3 A2 A1 R/W A0 D7 D6 ACK. BY NCT75 FRAME 1 SERIAL BUS ADDRESS BYTE D5 D4 D3 D2 D1 D0 FRAME 2 ADDRESS POINTER REGISTER BYTE 1 ACK. BY NCT75 9 SCL (CONTINUED) D7 SDA (CONTINUED) D6 D5 D4 D3 D2 D1 D0 ACK. BY STOP BY NCT75 MASTER FRAME 3 DATA BYTE Figure 6. Writing a Register Address to the Address Pointer Register, then Writing a Single Byte of Data to the Configuration Register 1 9 1 9 SCL SDA A6 START BY MASTER A5 A4 A3 A2 A1 A0 FRAME 1 SERIAL BUS ADDRESS BYTE R/W D7 SDA (CONTINUED) D9 D4 D3 D1 D0 1 9 D7 D8 D6 D5 D4 ACK. BY NCT75 FRAME 3 DATA BYTE D2 FRAME 2 ADDRESS POINTER REGISTER BYTE 9 D15 D14 D13 D12 D11 D10 D5 ACK. BY NCT75 1 SCL (CONTINUED) D6 ACK. BY NCT75 D3 D2 D1 D0 ACK. BY NCT75 FRAME 4 DATA BYTE STOP BY MASTER Figure 7. Writing to the Address Pointer Register Followed by Two Bytes of Data to a 16 Bit Limit Register 1 9 1 9 SCL SDA START BY MASTER A6 A5 A4 A3 A2 A1 A0 R/W ACK. BY NCT75 D7 D6 FRAME 1 SERIAL BUS ADDRESS BYTE D5 D4 D3 9 D1 D0 NO ACK. BY MASTER FRAME 2 DATA BYTE FROM REGISTER Figure 8. Reading Data from the Configuration Register http://onsemi.com D2 STOP BY MASTER NCT75 1 9 1 9 SCL SDA START BY MASTER A6 A5 A4 A3 A2 A1 A0 R/W FRAME 1 SERIAL BUS ADDRESS BYTE D15 D14 ACK. BY NCT75 D13 D12 D11 D10 D9 FRAME 2 MSB DATA FROM TEMPERATURE VALUE REGISTER 1 D8 ACK. BY MASTER 9 SCL (CONTINUED) SDA (CONTINUED) D7 D6 D5 D4 D3 D2 D1 D0 NO ACK. BY STOP BY MASTER MASTER FRAME 3 LSB DATA FROM TEMPERATURE VALUE REGISTER Figure 9. Reading Data from the Temperature Value Register Reading Data Reading data from the NCT75 is done in two different ways depending on the register being read. The configuration register is only 8 bits wide so a single byte read is used for this (shown in Figure 8). This consists of the device address followed by the data from the register. Reading the data in the temperature value register requires a two byte read (shown in Figure 9). This consists of the device address, followed by two bytes of data from the temperature register (the first byte is the MSB). In both cases the address pointer register of the register being read must be written to prior to performing a read operation. In Comparator Mode, the OS/ALERT pin becomes active when the measured temperature equals or exceeds the limit stored in the TOS setpoint register. The pin returns to its inactive status when the temperature drops below the THYST setpoint register value. OS/ALERT Output Overtemperature Modes The OS/ALERT output pin can operate in two different modes – overtemperature mode and SMBus alert mode. The pin defaults to overtemperature mode on power up. This means that it becomes active when the measured temperature meets or exceeds the limit stored in the TOS setpoint register. At this point it can deal with the event in one of two ways which depends on the mode it is in. The two overtemperature modes are: comparator mode and interrupt mode. Comparator mode is the default mode on power up. In the interrupt mode, the OS/ALERT pin becomes active when the temperature equals or exceeds the TOS limit for a consecutive number of faults. It can be reset by performing a read operation on any register in the NCT75. The output can only become active again when the TOS limit has been equalled or exceeded. Figure 10 shows how both the interrupt and comparator modes operate in relation to the output pin (OS/ALERT). It also shows the operation of the polarity bit in the configuration register. More information on comparator and interrupt modes alsong with the SMBus alert mode are explained below. Comparator Mode NOTE: Shutdown mode does not reset the output state for comparator mode. Interrupt Mode http://onsemi.com 10 NCT75 82C 81C TOS 80C Temperature 79C 78C 77C 76C 75C THYST 74C 73C 72C OS/ALERT PIN (COMPARATOR MODE) POLARITY = 0 OS/ALERT PIN (INTERRUPT MODE) POLARITY = 0 OS/ALERT PIN (COMPARATOR MODE) POLARITY = 1 Read Read Read OS/ALERT PIN (INTERRUPT MODE) POLARITY = 1 Figure 10. OS/ALERT Output Temperature Response Diagram Table 15. ORDERING INFORMATION Temperature Range Temperature Accuracy Package Description Package Option† NCT75DMR2G −55C to +125C 1C 8-lead Micro8t 3,000 Tape & Reel NCT75DR2G −55C to +125C 1C 8-lead SOIC 2,500 Tape & Reel NCT75MNR2G −55C to +125C 1C 8-lead DFN (2x2) 3,000 Tape & Reel Model Number* †For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D. *The “G’’ suffix indicates Pb-Free package available. http://onsemi.com 11 NCT75 PACKAGE DIMENSIONS DFN8 2x2, 0.5P CASE 506AA−01 ISSUE E D PIN ONE REFERENCE 2X 0.10 C 2X A B L1 ÇÇ ÇÇ 0.10 C DETAIL A E OPTIONAL CONSTRUCTIONS DIM A A1 A3 b D D2 E E2 e K L L1 ÉÉ ÉÉ EXPOSED Cu TOP VIEW A DETAIL B 0.10 C NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994 . 2. CONTROLLING DIMENSION: MILLIMETERS. 3. DIMENSION b APPLIES TO PLATED TERMINAL AND IS MEASURED BETWEEN 0.15 AND 0.20 MM FROM TERMINAL TIP. 4. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS. L L MOLD CMPD DETAIL B OPTIONAL CONSTRUCTION 0.08 C (A3) NOTE 4 SIDE VIEW DETAIL A A1 D2 1 4 C 8X SEATING PLANE RECOMMENDED SOLDERING FOOTPRINT* L 8 5 e/2 e 8X 1.30 PACKAGE OUTLINE E2 K MILLIMETERS MIN MAX 0.80 1.00 0.00 0.05 0.20 REF 0.20 0.30 2.00 BSC 1.10 1.30 2.00 BSC 0.70 0.90 0.50 BSC 0.30 REF 0.25 0.35 −−− 0.10 b 0.90 8X 0.50 2.30 0.10 C A B 0.05 C NOTE 3 1 BOTTOM VIEW 8X 0.30 0.50 PITCH DIMENSIONS: MILLIMETERS *For additional information on our Pb-Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. http://onsemi.com 12 NCT75 PACKAGE DIMENSIONS Micro8t CASE 846A−02 ISSUE H D HE PIN 1 ID NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION A DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.15 (0.006) PER SIDE. 4. DIMENSION B DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. INTERLEAD FLASH OR PROTRUSION SHALL NOT EXCEED 0.25 (0.010) PER SIDE. 5. 846A-01 OBSOLETE, NEW STANDARD 846A-02. E e b 8 PL 0.08 (0.003) T B M S A DIM A A1 b c D E e L HE S SEATING −T− PLANE 0.038 (0.0015) A A1 MILLIMETERS NOM MAX −− 1.10 0.08 0.15 0.33 0.40 0.18 0.23 3.00 3.10 3.00 3.10 0.65 BSC 0.40 0.55 0.70 4.75 4.90 5.05 MIN −− 0.05 0.25 0.13 2.90 2.90 L c SOLDERING FOOTPRINT* 8X 1.04 0.041 0.38 0.015 3.20 0.126 6X 8X 4.24 0.167 0.65 0.0256 5.28 0.208 SCALE 8:1 mm Ǔ ǒinches *For additional information on our Pb-Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. http://onsemi.com 13 INCHES NOM −− 0.003 0.013 0.007 0.118 0.118 0.026 BSC 0.016 0.021 0.187 0.193 MIN −− 0.002 0.010 0.005 0.114 0.114 MAX 0.043 0.006 0.016 0.009 0.122 0.122 0.028 0.199 NCT75 PACKAGE DIMENSIONS SOIC−8 NB CASE 751−07 ISSUE AK −X− NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION A AND B DO NOT INCLUDE MOLD PROTRUSION. 4. MAXIMUM MOLD PROTRUSION 0.15 (0.006) PER SIDE. 5. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.127 (0.005) TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM MATERIAL CONDITION. 6. 751−01 THRU 751−06 ARE OBSOLETE. NEW STANDARD IS 751−07. A 8 5 S B 0.25 (0.010) M Y M 1 4 −Y− K G C N DIM A B C D G H J K M N S X 45 _ SEATING PLANE −Z− 0.10 (0.004) H D 0.25 (0.010) M Z Y S X M J S MILLIMETERS MIN MAX 4.80 5.00 3.80 4.00 1.35 1.75 0.33 0.51 1.27 BSC 0.10 0.25 0.19 0.25 0.40 1.27 0_ 8_ 0.25 0.50 5.80 6.20 INCHES MIN MAX 0.189 0.197 0.150 0.157 0.053 0.069 0.013 0.020 0.050 BSC 0.004 0.010 0.007 0.010 0.016 0.050 0 _ 8 _ 0.010 0.020 0.228 0.244 SOLDERING FOOTPRINT* 1.52 0.060 7.0 0.275 4.0 0.155 0.6 0.024 1.270 0.050 SCALE 6:1 mm Ǔ ǒinches *For additional information on our Pb-Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. 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