MLX90616ESF-HCA

Infra Red Thermometer in TO-39

for high temperature thermometer guns

3901090616

Page 8 of 36

Data Sheet

Rev 002

August 20, 2012

8 Detailed description

8.1 Block diagram

Figure 3: block diagram

8.2 Signal processing principle

The operation of the MLX90616 is controlled by an internal state machine, which controls the measurements

and calculations of the object and ambient temperatures and does the post-processing of the temperatures to

output them through the PWM output or the SMBus compatible interface.

The output of the IR sensors is amplified by a low noise low offset chopper amplifier with programmable gain,

converted by a Sigma Delta modulator to a single bit stream and fed to a powerful DSP for further

processing. The signal is treated by programmable (by means of EEPROM content) FIR and IIR low pass

filters for further reduction of the bandwidth of the input signal to achieve the desired noise performance and

refresh rate. The output of the IIR filter is the measurement result and is available in the internal RAM. 3

different cells are available: One for the on-board temperature sensor (on chip PTAT or PTC) and 2 for the IR

sensors.

Based on results of the above measurements, the corresponding ambient temperature Ta and object

temperature To are calculated. Both calculated temperatures have a resolution of 0.02

˚C. The data for Ta

and To can be read in two ways: Reading RAM cells dedicated for this purpose via the 2-wire interface

(0.02°C resolution, fixed ranges), or through the PWM digital output (10 bit resolution, configurable range).

In the last step of the measurement cycle, the measured Ta and To are rescaled to the desired output

resolution of the PWM) and the recalculated data is loaded in the registers of the PWM state machine, which

creates a constant frequency with a duty cycle representing the measured data.

8.3 Block description

8.3.1 Amplifier

A low noise, low offset amplifier with programmable gain is used for amplifying the IR sensor voltage. By

carefully designing the input modulator and balanced input impedance, an offset below 0.5µV is achieved.

81101

OPA

ADC

DSP

PWM

STATE MACHINE

t°

Voltage

Regulator

90302