9

Typical application

Typical application circuit

The figure above shows a typical application schematic for the ALED8102S, Cled value depends on common rail

voltage connection length and driver total output current, typically it is around 47 µF; Cin is about 1 µF; current

resistor between R-EXT and GND should be connected as close as possible to the device.

result in a visible flash on connected LEDs (output stage undesired activation).

Device thermal management

The aim of this section is to provide some recommendation that can be useful to design the application PCB for a

better power dissipation:

•

To decrease the device working temperature, the package exposed pad needs soldering to the board.

•

To improve thermal performance at least a 4-layer (e.g. 2S2P) PCB should be used.

•

The copper area below the package thermal pad should be as wide as possible also outside the package

perimeter (using the package sides without pins)

•

A reasonable number of vias must connect the copper area below the package to all available PCB layers

especially just below the device package (e.g. 3x3 or 4x3 vias array) but also outside the package perimeter.

The smaller and closely spaced vias are, the better solution is. The best implementation is represented by

copper filled vias.

•

On each inner layer a copper area must be provided for dissipation (wider it is better, if possible at least

4 times or more the package dimensions). A good condition is to have at least a power layer as an entire

copper area (e.g. GND layer)

•

Traces for pin connection must be as wide as layout constrains allow

•

Several devices in power dissipation on the same board must be properly spaced.

Figure 9 shows, once the maximum power dissipation is fixed, which ambient temperature range can be covered

according to the maximum junction temperature and package thermal resistance: 37.5 °C/W for HTSSOP16 on

Jedec PCB (2S2P) and conditions. With the same thermal resistance, figure 10 shows the junction temperature

as a function of ambient temperature considering 1 W of power dissipation.

ALED8102S

Typical application

DS12430 - Rev 2

page 10/19