adt7401rt-reel7 Analog Devices, Inc., adt7401rt-reel7 Datasheet - Page 9

• Manufacturer Part Number: adt7401rt-reel7
• Description: Smbus/i2c Compatible, ?0.5?c Accurate 12-bit Digital Temperature Sensor With Daisy Chain
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
CIRCUIT INFORMATION
The ADT7401 is a standalone temperature sensor that generates
a 12-bit digital output in two’s complement that varies in direct
proportion with the temperature of the device. An onboard
sensor generates a voltage precisely proportional to absolute
temperature which is compared to an internal voltage reference
and input to a precision digital modulator. The serial digital
output is converted into a 12-bit digital word and stored in the
Temperature Value Register. Overall accuracy is ±5°C from 0°C
to +70°C, with excellent transducer linearity. The digital output
of the ADT7401 is SMBus/I
interfaced to most popular microcontrollers.
The onboard temperature sensor has excellent accuracy and
linearity over the entire rated temperature range without
correction or calibration by the user.
The sensor output is digitized by a first-order sigma-delta
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 12 bits
of effective accuracy in an extremely compact circuit.
CONVERTER DETAILS
The sigma-delta modulator consists of an input sampler, a
summing network, an integrator, a comparator, and a 1-bit
DAC. Similar to the voltage-to-frequency converter, this
architecture creates in effect a negative feedback loop whose
intent is to minimize the integrator output by changing the duty
2
C compatible, and is easily
Rev. PrE | Page 9 of 12
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 is
called oversampling. This 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, which results in a serial digital signal. This
signal is then converted into a 12-bit digital word for storage
into a register. The final output format is two’s complement.
Figure 14. First-Order Sigma-Delta Modulator
ADT7401