MLX90616 Datasheet, PDF (32/36 Pages) Melexis Microelectronic Systems – Infra Red Thermometer in TO-39 for high temperature thermometer guns

MLX90616ESF-HCA
Infra Red Thermometer in TO-39
for high temperature thermometer guns
For ESD protection there are clamp diodes between the Vss and Vdd and each of the other pins. This
means that the MLX90616 might draw current from a bus in case the SCL and/or SDA is connected and the
Vdd is lower than the bus pull-ups’ voltage.
A sleep mode is available in the MLX90616Bxx. This mode is entered and exited via the SMBus compatible
2-wire communication. On the other hand, the extended functionality of the SCL pin yields increased leakage
current through that pin. As a result, this pin needs to be forced low in sleep mode and the pull-up on the SCL
line needs to be disabled in order to keep the overall power drain in sleep mode really small. During sleep
mode the sensor will not perform measurements.
The PWM pin is not designed for direct drive of inductive loads (such as electro-magnetic relays). Some
drivers need to be implemented for higher load, and auxiliary protection might be necessary even for light but
inductive loading.
It is possible to use the MLX90616xxx in applications, powered directly from the AC line (transformer less). In
such cases it is very important not to forget that the metal package of the sensor is not isolated and
therefore may become connected to that line and have that electric potential present too. Melexis can not be
responsible for any application like this and highly recommends not using the MLX90616xxx in that way.
Power dissipation within the package may affect performance in two ways: by heating the “ambient”
sensitive element significantly beyond the actual ambient temperature, as well as by causing gradients over
the package that will inherently cause thermal gradient over the cap. Loading the outputs also causes
increased power dissipation. In case of using the MLX906166xx 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 LSB error.
Power supply decoupling capacitor is needed as with most integrated circuits. MLX90616 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 MLX90616 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 an increase to the ESD rating is
possible.
Check www.melexis.com for most recent application notes about MLX90616.
3901090616
Rev 002
Page 32 of 36
Data Sheet
August 20, 2012