DLPS037F October 2014 – June 2021 DLPC900
The thermal limitation for the DLPC900 is that the maximum operating junction temperature (TJ) must not be exceeded (this is defined in Section 6.3). This temperature is dependent on operating ambient temperature, airflow, PCB design (including the component layout density and the amount of copper used), power dissipation of the DLPC900, and power dissipation of surrounding components. The DLPC900 device package is designed primarily to extract heat through the power and ground planes of the PCB, thus copper content and airflow over the PCB are important factors.
The recommended maximum operating ambient temperature (TA) is provided primarily as a design target and is based on maximum DLPC900 power dissipation and RθJA at 1 m/s of forced airflow, where RθJA is the thermal resistance of the package as measured using a JEDEC-defined standard test PCB. This JEDEC test PCB is not necessarily representative of the DLPC900 PCB, and thus the reported thermal resistance can be inaccurate in the actual product application. Although the actual thermal resistance can be different, it is the best information available during the design phase to estimate thermal performance. However after the PCB is designed and the product is built, it is highly recommended thermal performance be measured and validated.
To do this, the top-center case temperature must be measured under the worst case product scenario (max power dissipation, max voltage, max ambient temp) and validated not to exceed the maximum recommended case temperature (TC). This specification is based on the measured φJT for the DLPC900 package and provides a relatively accurate correlation to junction temperature. Care must be taken when measuring this case temperature to prevent accidental cooling of the package surface. It is recommended to use a small (approximately 40 gauge) thermocouple. The bead and the thermocouple wire must be covered with a minimal amount of thermally conductive epoxy and contact the top of the package. The wires are routed closely along the package and the board surface to avoid cooling the bead through the wires.