Application information

LD39100

16/27

DocID15676 Rev 6

Regarding the adjustable version, the output voltage can be adjusted from 0.8 V up to the

input voltage, minus the voltage drop across the pass element (dropout voltage), by

connecting a resistor divider between ADJ pin and the output, thus allowing remote voltage

sensing.

The resistor divider should be selected as follows:

Equation 1

Resistors should be used with values in the range from 10 kΩ to 50 kΩ. Lower values can

also be suitable, but they increase current consumption.

6.1

Power dissipation

An internal thermal feedback loop disables the output voltage if the die temperature rises to

approximately 160 °C. This feature protects the device from excessive temperature and

allows the user to push the limits of the power handling capability of a given circuit board

without the risk of damaging the device.

A good PC board layout should be used to maximize power dissipation. The thermal path

for the heat generated by the device is from the die to the copper lead frame, through the

package leads and exposed pad, to the PC board copper. The PC board copper acts as a

heatsink. The footprint copper pads should be as wide as possible to spread and dissipate

the heat to the surrounding ambient. Feed-through vias to the inner or backside copper

layers are also useful to improve the overall thermal performance of the device.

The device power dissipation depends on the input voltage, output voltage and output

current, and is given by:

Equation 2

Junction temperature of the device is:

Equation 3

where: