MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
power dissipation. In case of using the MLX90614Axx internal zener voltage feature, the regulating external
transistor should also not cause heating of the TO39 package.
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 LSBs 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 003
Page 34 of 40
Data Sheet
03/Oct/2007
MELEXIS [ Melexis Microelectronic Systems ]
