Datasheet ADT7422 (Analog Devices) - 11

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Data Sheet ADT7422 TEMPERATURE DATA FORMAT TEMPERATURE CONVERSION FORMULAS
One LSB of the ADC corresponds to 0.0625°C in 13-bit mode
16-Bit Temperature Data Format
or 0.0078°C in 16-bit mode. The ADT7422 can measure a Use the following formulas to calculate the measured temperature range of 255°C, and is guaranteed to measure a low temperatures in °C from the ADT7422 output codes in 16-bit value temperature limit of −40°C to a high value temperature format: limit of +125°C. The temperature measurement result is stored Positive Temperature = ADC Code (Decimal)/128 in the 16-bit temperature value register and is compared with the high temperature limits stored in the 16-bit T Negative Temperature = (ADC Code (Decimal) − CRIT setpoint register (consisting of the 8-bit T 65,536)/128 CRIT setpoint most significant byte register and the 8-bit TCRIT setpoint least significant byte where ADC Code uses all 16 bits of the data byte, including the register) and the 16-bit THIGH setpoint register (consisting of the sign bit. 8-bit THIGH setpoint most significant byte register and the 8-bit Negative Temperature = (ADC Code (Decimal) − THIGH setpoint least significant byte register). The temperature 32,768)/128 value is also compared to the low temperature limit stored in the T where Bit 15 (sign bit) is removed from the ADC code. LOW setpoint register, which consists of the 8-bit TLOW setpoint most significant byte register and the 8-bit TLOW setpoint least
13-Bit Temperature Data Format
significant byte register. Use the following formulas to calculate the measured Temperature data in the temperature value register, the TCRIT temperatures in °C from the ADT7422 output codes in 13-bit setpoint register, the THIGH setpoint register, and the TLOW setpoint format: register are represented by a 13-bit twos complement word. Positive Temperature = ADC Code (Decimal)/16 The MSB is the temperature sign bit. The three LSBs, Bits[2:0], at power-up, are not part of the temperature conversion result and Negative Temperature = (ADC Code (Decimal) − 8192)/16 are flag bits for TCRIT, THIGH, and TLOW. Table 6 shows the 13-bit where ADC Code uses the first 13 MSBs of the data byte, temperature data format without Bits[2:0]. including the sign bit. To extend the number of bits in the temperature data-word to Negative Temperature = (ADC Code (Decimal) − 4096)/16 16 bits (twos complement), set Bits[7:1] in the configuration where Bit 15 (sign bit) is removed from the ADC code. register (Register Address 0x03). When using a 16-bit temperature data value, Bits[2:0] are not used as flag bits and are the LSB bits
10-Bit Temperature Data Format
of the temperature value instead. The power-on default setting Use the following formulas to calculate the measured has a 13-bit temperature data value. temperatures in °C from the ADT7422 output codes in 10-bit A 2-byte read is required to read back the temperature from the format: temperature value register. The ADT7422 can still be used with a Positive Temperature = ADC Code (Decimal)/2 9-bit temperature data format if the last four LSBs of the 13-bit Negative Temperature = (ADC Code (Decimal) − 1024)/2 temperature value are ignored. These four LSBs are Bits[6:3] in Table 6. where ADC Code uses all 10 bits of the data byte, including the sign bit.
Table 6. 13-Bit Temperature Data Format
Negative Temperature = (ADC Code (Decimal) − 512)/2
Digital Output (Binary) Digital Output Temperature Bits[15:3] (Hexadecimal)
where Bit 9 (sign bit) is removed from the ADC code. −40°C 1 1101 1000 0000 0x1D80
9-Bit Temperature Data Format
−25°C 1 1110 0111 0000 0x1E70 −0.0625°C 1 1111 1111 1111 0x1FFF Use the following formulas to calculate the measured temperatures in °C from the ADT7422 output codes in 9-bit 0°C 0 0000 0000 0000 0x000 format: +0.0625°C 0 0000 0000 0001 0x001 +25°C 0 0001 1001 0000 0x190 Positive Temperature = ADC Code (Decimal) +105°C 0 0110 1001 0000 0x690 Negative Temperature = ADC Code (Decimal) − 512 +125°C 0 0111 1101 0000 0x7D0 where ADC Code uses all nine bits of the data byte, including +150°C 0 1001 0110 0000 0x960 the sign bit. Negative Temperature = ADC Code (Decimal) − 256 where Bit 8 (sign bit) is removed from the ADC code. Rev. 0 | Page 11 of 23 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION PRODUCT HIGHLIGHTS FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS I2C TIMING SPECIFICATIONS Timing Diagram ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION CIRCUIT INFORMATION CONVERTER DETAILS NORMAL MODE ONE SHOT MODE CT and INT Operation in One Shot Mode 1 SPS MODE SHUTDOWN MODE FAULT QUEUE TEMPERATURE DATA FORMAT TEMPERATURE CONVERSION FORMULAS 16-Bit Temperature Data Format 13-Bit Temperature Data Format 10-Bit Temperature Data Format 9-Bit Temperature Data Format REGISTERS ADDRESS POINTER REGISTER TEMPERATURE VALUE REGISTERS STATUS REGISTER CONFIGURATION REGISTER THIGH SETPOINT REGISTERS TLOW SETPOINT REGISTERS TCRIT SETPOINT REGISTERS THYST SETPOINT REGISTER ID REGISTER SERIAL INTERFACE SERIAL BUS ADDRESS WRITING DATA READING DATA RESET GENERAL CALL INT AND CT OUTPUTS UNDERTEMPERATURE AND OVERTEMPERATURE DETECTION Comparator Mode Interrupt Mode APPLICATIONS INFORMATION THERMAL RESPONSE TIME SUPPLY DECOUPLING POWERING FROM A SWITCHING REGULATOR TEMPERATURE MEASUREMENT QUICK GUIDE TO MEASURING TEMPERATURE OUTLINE DIMENSIONS ORDERING GUIDE