Power Good function requires an external pull-up resistor, which may be connected to any potential lower than

5.5 V. PG pin typical current capability is up to 1 mA, so it is advisable to choose a pull-up resistor in the range

from 10 kΩ to 1 MΩ. If Power Good function is not used, PG pin has to remain floating.

6.4

Protection features

Current limit

The LD59150 embeds a constant-current limit circuit, which acts in case of overload or short-circuit on the output,

clamping the load current to a safe value (typ. 3 A).

Normal operation is restored if the overload disappears, but prolonged operation in current limit may lead to high

power dissipation inside the LDO and therefore to thermal shutdown.

Thermal potection

An internal thermal feedback loop disables the output voltage if the die temperature reaches approximately 165

°C. This feature protects the device from an excessive temperature that could lead to a permanent damage of the

LDO.

Once the thermal protection is triggered and the device is shut down, normal operation is automatically recovered

if the die temperature falls below 145 °C (thermal protection hysteresis of 20 °C typically).

Current and thermal limit protections are designed to protect the LDO from an excessive power dissipation and

not intended to replace a proper thermal and electrical design of the application. Continuous operation above the

maximum ratings may lead to permanent damage of the device.

6.5

Power dissipation

An accurate PCB design is recommended, to ensure that the device internal junction temperature is kept below

150 °C, in all the operating conditions. The thermal energy generated by the device flows from the die surface to

the PCB copper area through the package leads.

The PCB copper area acts as a heat sink. The footprint copper pads should be as wide as possible to spread

and dissipate the heat to the surrounding environment. Thermal micro-vias to the inner or backside copper layers

improve the overall thermal performance of the device.

The power dissipation of the LDO depends on the input voltage, output voltage and output current and is given

by:

PD = (VIN - VOUT) x IOUT

(2)

The junction temperature of the device is:

TJ_MAX = TA + RthJA x PD

(3)

where: TJ_MAX is the maximum allowable junction temperature of the die, 150 °C; TA is the ambient temperature;

RthJA is the thermal resistance junction-to-ambient.

With the above equation it is possible to calculate the maximum allowable power dissipation, therefore the

maximum load current for a certain voltage drop. Appropriate de-rating of the operating conditions should be

applied accordingly.

LD59150

Protection features

DS12455 - Rev 5

page 9/22