GENERAL DESCRIPTION

The ADT7420 is a high accuracy digital temperature sensor offering breakthrough performance over a wide industrial range, housed in a 4 mm × 4 mm LFCSP package. It contains an internal band gap reference, a temperature sensor, and a 16-bit ADC to monitor and digitize the temperature to 0.0078°C resolution. The ADC resolution, by default, is set to 13 bits (0.0625°C). The ADC resolution is a user programmable mode that can be changed through the serial interface.
The ADT7420 is guaranteed to operate over supply voltages from 2.7 V to 5.5 V. Operating at 3.3 V, the average supply current is typically 210 μA. The ADT7420 has a shutdown mode that powers down the device and offers a shutdown current of typically 2.0 μA at 3.3 V. The ADT7420 is rated for operation over the −40°C to +150°C temperature range.
Pin A0 and Pin A1 are available for address selection, giving the ADT7420 four possible I2C addresses. The CT pin is an opendrain output that becomes active when the temperature exceeds a programmable critical temperature limit. The INT pin is also an open-drain output that becomes active when the temperature exceeds a programmable limit. The INT pin and CT pin can operate in comparator and interrupt event modes.

 

PRODUCT HIGHLIGHTS

1.Ease of use, no calibration or correction required by the user.
2.Low power consumption.
3.Excellent long-term stability and reliability.
4. High accuracy for industrial, instrumentation, and medical applications.
5. Packaged in a 16-lead, 4 mm × 4 mm LFCSP RoHS compliant package.

 

FEATURES

High performance
Temperature accuracy
±0.20°C from -10°C to +85°C at 3.0 V
±0.25°C from -20°C to +105°C from 2.7 V to 3.3 V
16-bit resolution: 0.0078°C
Ultralow temperature drift: 0.0073°C
NIST traceable or equivalent
Fast first temperature conversion on power-up of 6 ms
Easy implementation
No temperature calibration/correction required by user
No linearity correction required
Low power
Power-saving 1 sample per second (SPS) mode
700 µW typical at 3.3 V in normal mode
7 µW typical at 3.3 V in shutdown mode
Wide operating ranges
Temperature range: −40°C to +150°C
Voltage range: 2.7 V to 5.5 V
Programmable interrupts
Critical overtemperature interrupt
Overtemperature/undertemperature interrupt
I²C-compatible interface
16-lead, 4 mm × 4 mm LFCSP RoHS-compliant package

 

APPLICATIONS

RTD and thermistor replacement
Thermocouple cold junction compensation
Medical equipment
Industrial control and test
Food transportation and storage
Environmental monitoring and HVAC
Laser diode temperature control

 

THEORY OF OPERATION

CIRCUIT INFORMATION

The ADT7420 is a high accuracy digital temperature sensor that uses a 16-bit ADC to monitor and digitize the temperature to 0.0078°C of resolution. The ADC resolution, by default, is set to 13 bits (0.0625°C). An internal temperature sensor generates a voltage proportional to absolute temperature, which is compared to an internal voltage reference and input into a precision digital modulator.
The internal temperature sensor has high accuracy and linearity over the entire rated temperature range without needing correction or calibration by the user.
The sensor output is digitized by a sigma-delta (Σ-Δ) modulator, also known as the charge balance type analog-to-digital converter. This type of converter utilizes time-domain oversampling and a high accuracy comparator to deliver 16 bits of resolution in an extremely compact circuit.

CONVERTER DETAILS

The Σ-Δ modulator consists of an input sampler, a summing network, an integrator, a comparator, and a 1-bit DAC. This 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.