Datasheet ADT7310 (Analog Devices) - 9

Data Sheet ADT7310 THEORY OF OPERATION CIRCUIT INFORMATION Σ-∆ MODULATOR
The ADT7310 is a 13-bit digital temperature sensor that is
INTEGRATOR COMPARATOR
extendable to 16-bits for greater resolution. An on-board
VOLTAGE REF
temperature sensor generates a voltage proportional to absolute
AND VPTAT
temperature, which is compared to an internal voltage reference and input to a precision digital modulator.
1-BIT DAC
The on-board temperature sensor has excellent accuracy and linearity over the entire rated temperature range without
1-BIT
needing correction or calibration by the user.
CLOCK LPF DIGITAL TEMPERATURE
12
GENERATOR FILTER VALUE
-0 The sensor output is digitized by a sigma-delta (Σ-Δ)
13-BIT REGISTER
789 7 0 modulator, also known as the charge balance type analog-to- Figure 13. Σ-∆ Modulator digital converter. This type of converter utilizes time-domain oversampling and a high accuracy comparator to deliver
TEMPERATURE MEASUREMENT
16-bits of resolution in an extremely compact circuit. In normal mode, the ADT7310 runs an automatic conversion sequence. During this automatic conversion sequence, a conver- Configuration register functions consist of sion takes 240 ms to complete and the ADT7310 is continuously converting. This means that as soon as one temperature conver- Switching between 13-bit and 16-bit resolution sion is completed, another temperature conversion begins. Each Switching between normal operation and full power-down temperature conversion result is stored in the temperature value Switching between comparator and interrupt event modes register and is available through the SPI interface. In continuous on the INT and CT pins conversion mode, the read operation provides the most recent Setting the active polarity of the CT and INT pins converted result. Setting the number of faults that activate CT and INT Enabling the standard one-shot mode and 1 SPS mode On power-up, the first conversion is a fast conversion, taking typically 6 ms. If the temperature exceeds 147°C, the CT pin
CONVERTER DETAILS
asserts low. If the temperature exceeds 64°C, the INT pin asserts The Σ-Δ modulator consists of an input sampler, a summing low. Fast conversion temperature accuracy is typically within ±5°C. network, an integrator, a comparator, and a 1-bit DAC. This The conversion clock for the part is generated internally. architecture creates a negative feedback loop and minimizes the No external clock is required except when reading from and integrator output by changing the duty cycle of the comparator writing to the serial port. output in response to input voltage changes. The comparator samples the output of the integrator at a much higher rate than The measured temperature value is compared with a critical the input sampling frequency. This oversampling spreads the temperature limit (stored in the 16-bit TCRIT setpoint read/write quantization noise over a much wider band than that of the register), a high temperature limit (stored in the 16-bit THIGH input signal, improving overall noise performance and setpoint read/write register), and a low temperature limit (stored increasing accuracy. in the 16-bit TLOW setpoint read/write register). If the measured value exceeds these limits, the INT pin is activated; and if it The modulated output of the comparator is encoded using a exceeds the TCRIT limit, the CT pin is activated. The INT and CT circuit technique that results in SPI temperature data. pins are programmable for polarity via the configuration register, and the INT and CT pins are also programmable for interrupt mode via the configuration register. Rev. A | Page 9 of 24 Document Outline Features Applications General Description Functional Block Diagram Revision History Specifications SPI Timing Specifications Absolute Maximum Ratings ESD Caution Pin Configuration 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 Continuous Read 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 Status Register Configuration Register Temperature Value Register ID Register TCRIT Setpoint Register THYST Setpoint Register THIGH Setpoint Register TLOW Setpoint Register Serial Interface SPI Command Byte Writing Data Reading Data Interfacing to DSPs or Microcontrollers Serial Interface Reset 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