Datasheet

Application information
LDL1117
10/20
DocID030319 Rev 3
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 peak current available for a defined drop voltage (V
IN
-V
OUT
) is shown in Section 7:
"Typical performance characteristics".
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 T
J-OP
, the following formula is used:
Equation 1
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
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P
DMAX
should be also derated according to the maximum current allowed by the SOA
protection.
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.
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: "Stability plan (VOUT = 5 V)" and Figure 21: "Stability plan (VOUT =
1.2 V)".
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.