6

Application information

6.1

Thermal and short-circuit protections

The LDL1117 is self-protected from short-circuit conditions and overtemperature. When the output load is higher

than the one supported by the device, the output current rises until the limit of typically 2 A is reached. The current

limit value is dependent of the dissipated power, thanks to an additional SOA protection, so that the maximum

power is limited.

The thermal protection occurs when the junction temperature reaches typically 175 °C. The IC enters the

shutdown status. As soon as the junction temperature falls again below 150 °C (typ.) the device starts working

again.

In order to calculate the maximum power that the device can dissipate, keeping the junction temperature below

(1)

6.2

Input and output capacitor selection

The LDL1117 requires external capacitors to assure the regulator control loop stability.

Any good quality ceramic capacitor can be used but, the X5R and the X7R are suggested since they guarantee a

very stable combination of capacitance and ESR over the temperature range. The input/output capacitors should

be placed as close as possible to the relative pins. The LDL1117 requires an input capacitor with a minimum value

of 1 μF.

The device is also equipped with a differential thermal protection that avoid damage in case of fast thermal

gradients inside the chip. When the differential thermal protection is activated both channel and the LDO are

switched off. This protection works in auto-retry mode, the device restarts automatically when the thermal

conditions go back into the normal operating region.

This capacitor must be placed as close as possible to the input pin of the device and returned to a clean analog

ground. The control loop of the LDL1117 is designed to work with an output ceramic capacitor. Other type of

capacitors may be used, as long as they meet the requirements of minimum capacitance and equivalent series

resistance (ESR), as shown in Figure 20 and Figure 21.

To assure stability, the output capacitor must maintain its ESR and capacitance in the stable region, over the full

operating temperature range.

The suggested combination of 1 μF input and 4.7 μF output capacitors offers a good compromise among the

stability of the regulator, optimum transient response and total PCB area occupation.

LDL1117

Application information

DS12022 - Rev 6

page 7/23