MLX90614_15 Datasheet, PDF (43/51 Pages) Melexis Microelectronic Systems – Single and Dual Zone Infra Red Thermometer in TO-39

MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
High capacitive load on a PWM line will result in significant charging currents from the power supply,
bypassing the capacitor and therefore causing EMC, noise, level degradation and power dissipation problems.
A simple option is adding a series resistor between the PWM / SDA pin and the capacitive loaded line, in which
case timing specifications have to be carefully reviewed. For example, with a PWM output that is set to 1.024
ms and the output format that is 11 bit, the time step is 0.5 µs and a settling time of 2 µs would introduce a 4
LSB error.
Power supply decoupling capacitor is needed as with most integrated circuits. MLX90614 is a mixed-
signal device with sensors, small signal analog part, digital part and I/O circuitry. In order to keep the noise low
power supply switching noise needs to be decoupled. High noise from external circuitry can also affect noise
performance of the device. In many applications a 100nF SMD ceramic capacitor close to the Vdd and Vss pins
would be a good choice. It should be noted that not only the trace to the Vdd pin needs to be short, but also the
one to the Vss pin. Using MLX90614 with short pins improves the effect of the power supply decoupling.
Severe noise can also be coupled within the package from the SCL (in worst cases also from the SDA) pin. This
issue can be solved by using PWM output. Also the PWM output can pass additional filtering (at lower PWM
frequency settings). With a simple LPF RC network added also increase of the ESD rating is possible.
Check www.melexis.com for most recent application notes about MLX90614.
3901090614
Rev 009
Page 43 of 52
Data Sheet
June 29, 2015