Datasheet ADT7410 (Analog Devices) - 9

Data Sheet ADT7410 THEORY OF OPERATION CIRCUIT INFORMATION TEMPERATURE MEASUREMENT
The ADT7410 is a 13-bit digital temperature sensor that In normal mode, the ADT7410 runs an automatic conversion is extendable to 16 bits for greater resolution. An on-board sequence. During this automatic conversion sequence, a conversion temperature sensor generates a voltage proportional to absolute takes 240 ms to complete and the ADT7410 is continuously temperature, which is compared to an internal voltage reference converting. This means that as soon as one temperature conversion and input to a precision digital modulator. is completed, another temperature conversion begins. Each The on-board temperature sensor has excellent accuracy temperature conversion result is stored in the temperature value and linearity over the entire rated temperature range without registers and is available through the I2C interface. In continuous needing correction or calibration by the user. conversion mode, the read operation provides the most recent converted result. The sensor output is digitized by a Σ-Δ modulator, also known as the charge balance type analog-to-digital converter. This type of On power-up, the first conversion is a fast conversion, taking converter uses time domain oversampling and a high accuracy typically 6 ms. If the temperature exceeds 147°C, the CT pin comparator to deliver 16 bits of resolution in an extremely asserts low. If the temperature exceeds 64°C, the INT pin asserts compact circuit. low. Fast conversion temperature accuracy is typically within ±5°C. Configuration register functions consist of The conversion clock for the part is generated internally. No external clock is required except when reading from and Switching between 13-bit and 16-bit resolution writing to the serial port. Switching between normal operation and full power-down The measured temperature value is compared with a critical Switching between comparator and interrupt event modes temperature limit (stored in the 16-bit TCRIT setpoint read/write on the INT and CT pins register), a high temperature limit (stored in the 16-bit T HIGH set- Setting the active polarity of the CT and INT pins point read/write register), and a low temperature limit (stored in Setting the number of faults that activate CT and INT the 16-bit TLOW setpoint read/write register). If the measured value Enabling the standard one-shot mode and 1 SPS mode exceeds these limits, the INT pin is activated; and if it exceeds the
CONVERTER DETAILS
TCRIT limit, the CT pin is activated. The INT and CT pins are programmable for polarity via the configuration register, and the The Σ-Δ modulator consists of an input sampler, a summing INT and CT pins are also programmable for interrupt mode via network, an integrator, a comparator, and a 1-bit DAC. This the configuration register. architecture creates a negative feedback loop and minimizes the integrator output by changing the duty cycle of the comparator output in response to input voltage changes. The comparator samples the output of the integrator at a much higher rate than the input sampling frequency. This oversampling spreads the quantization noise over a much wider band than that of the input signal, improving overall noise performance and increasing accuracy. The modulated output of the comparator is encoded using a circuit technique that results in I2C temperature data.
Σ-∆ MODULATOR INTEGRATOR COMPARATOR VOLTAGE REF AND VPTAT 1-BIT DAC 1-BIT CLOCK LPF DIGITAL TEMPERATURE
2
GENERATOR FILTER VALUE
-01 60
13-BIT REGISTER
65 0 Figure 12. Σ-Δ Modulator Rev. C | Page 9 of 24 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS I2C TIMING SPECIFICATIONS Timing Diagram ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION CIRCUIT INFORMATION CONVERTER DETAILS TEMPERATURE MEASUREMENT ONE-SHOT MODE 1 SPS MODE CT and INT Operation in One-Shot Mode SHUTDOWN 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 TEMPERATURE MONITORING OUTLINE DIMENSIONS ORDERING GUIDE