ADT7410TRZ-REEL Просмотр технического описания (PDF) - Analog Devices

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ADT7410TRZ-REEL

±0.5°C Accurate, 16-Bit Digital I²C Temperature Sensor

Analog Devices 

ADT7410

THEORY OF OPERATION

CIRCUIT INFORMATION

The ADT7410 is a 13-bit digital temperature sensor that is extend-

able to 16 bits for greater resolution. An on-board temperature

sensor generates a voltage proportional to absolute temperature,

which is compared to an internal voltage reference and input to a

precision digital modulator.

The on-board temperature sensor has excellent 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 conver-

ter. This type of converter utilizes time-domain oversampling

and a high accuracy comparator to deliver 16 bits of resolution

in an extremely compact circuit.

Configuration register functions consist of

• Switching between 13-bit and 16-bit resolution

• Switching between normal operation and full power-down

• Switching between comparator and interrupt event modes

on the INT and CT pins

• Setting the active polarity of the CT and INT pins

• Setting the number of faults that activate CT and INT

• Enabling the standard one-shot mode and 1 SPS mode

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.

The modulated output of the comparator is encoded using

a circuit technique that results in I2C temperature data.

VOLTAGE REF

AND VPTAT

Σ-Δ MODULATOR

INTEGRATOR

COMPARATOR

TEMPERATURE MEASUREMENT

In normal mode, the ADT7410 runs an automatic conversion

sequence. During this automatic conversion sequence, a conver-

sion takes 240 ms to complete and the ADT7410 is continuously

converting. This means that as soon as one temperature conver-

sion is completed, another temperature conversion begins. Each

temperature conversion result is stored in the temperature value

registers and is available through the I2C interface. In continuous

conversion mode, the read operation provides the most recent

converted result.

On power-up, the first conversion is a fast conversion, taking

typically 6 ms. If the temperature exceeds 147°C, the CT pin

asserts low. If the temperature exceeds 64°C, the INT pin asserts

low. Fast conversion temperature accuracy is typically within ±5°C.

The conversion clock for the part is generated internally.

No external clock is required except when reading from

and writing to the serial port.

The measured temperature value is compared with a critical

temperature limit (stored in the 16-bit TCRIT setpoint read/write

register), a high temperature limit (stored in the 16-bit THIGH set-

point read/write register), and a low temperature limit (stored

in the 16-bit TLOW setpoint read/write register). If the measured

value exceeds these limits, the INT pin is activated; and if it exceeds

the TCRIT limit, the CT pin is activated. The INT and CT 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.

CLOCK

GENERATOR

1-BIT

DAC

1-BIT

LPF DIGITAL

FILTER

TEMPERATURE

VALUE

13-BIT REGISTER

Figure 12. Σ-Δ Modulator

Rev. 0 | Page 9 of 24

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