DLPC3470 datasheet(62/70 Pages) TI1

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DLPC3470

DLPS110 – APRIL 2018

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11.1.10 Thermal Considerations

The underlying thermal limitation for the DLPC3470 controller is that the maximum operating junction

temperature (TJ) not be exceeded (this is defined in the ). 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 DLPC3470 controller , and power dissipation of surrounding components. The

DLPC3470 controller ’s 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 DLPC3470 controller power dissipation and RθJA at 0 m/s of forced airflow, where RθJA is the

thermal resistance of the package as measured using a glater test PCB with two, 1-oz power planes. This

JEDEC test PCB is not necessarily representative of the DLPC3470 controller PCB; the reported thermal

resistance may not be accurate in the actual product application. Although the actual thermal resistance may 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, TI highly recommended that thermal performance be

measured and validated.

To do this, measure the top center case temperature under the worse case product scenario (max power

dissipation, max voltage, max ambient temperature) and validated not to exceed the maximum recommended

case temperature (TC). This specification is based on the measured φJT for the DLPC3470 controller package

and provides a relatively accurate correlation to junction temperature. Take care when measuring this case

temperature to prevent accidental cooling of the package surface. TI recommends a small (approximately 40

gauge) thermocouple. The bead and thermocouple wire should contact the top of the package and be covered

with a minimal amount of thermally conductive epoxy. The wires should be routed closely along the package and

the board surface to avoid cooling the bead through the wires.

11.2 Layout Example

Figure 37. Layout Recommendation

DLPC3470 Datasheet(PDF) 62 Page - Texas Instruments