LD39150xx

Application notes

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7

Application notes

7.1

External capacitors

The LD39150xx requires external capacitors for regulator stability. These capacitors must be

selected to meet the requirements of minimum capacitance and equivalent series resistance

(see Figure 15 and Figure 16). The input/output capacitors must be located less than 1cm

from the relative pins and connected directly to the input/output ground pins using traces

which have no other currents flowing through them. Any good quality of Ceramic or

Electrolytic capacitors can be used.

7.2

Input capacitor

An input capacitor whose minimum value is 1 µF is required with the LD39150xx (amount of

capacitance can be increased without limit). This capacitor must be located a distance of not

more than 1cm from the input pin of the device and returned to a clean analog ground. Any

good quality ceramic, tantalum or film capacitors can be used for this capacitor.

7.3

Output capacitor

It is possible to use ceramic or tantalum capacitors but the output capacitor must meet the

requirement for minimum amount of capacitance and ESR (equivalent series resistance)

value. A minimum capacitance of 2.2 µF is a good choice to guarantee the stability of the

showing the allowable ESR range as a function of the output capacitance. This curve

7.4

Thermal note

The output capacitor must maintain its ESR in the stable region over the full operating

temperature range to assure stability. Also, capacitors tolerance and variation with

temperature must be kept in consideration in order to assure the minimum amount of

capacitance at all times.

7.5

Inhibit input operation

The inhibit pin can be used to turn OFF the regulator when pulled down, so drastically

reducing the current consumption down to less than 1 µA. When the inhibit feature is not

proper operation, the signal source used to drive the inhibit pin must be able to swing above

The inhibit pin must not be left floating because it is not internally pulled down/up.