DocID025199 Rev 2

11/27

LD39130S

Application information

5

Application information

5.1

Soft-start function

The LD39130S has an internal soft-start circuit. By increasing the startup time up to 100 µs,

without the need of any external soft-start capacitor, this feature keeps the regulator inrush

current at startup under control.

5.2

Auto green mode function

The LD39130S integrates an internal logic circuitry, which allows the regulator to be in ultra

low consumption mode (green mode), when the output current required is very low.

When the auto green mode is enabled, the regulator automatically selects its operating

mode, switching from a very low consumption operation at light loads, to a very fast

transient response mode when the load current increases.

In the LD39130S, in DFN6 package, this function can be disabled by the user, by means of

an external logic pin (GM). When the GM pin is set at high logic level, the device always

operates in normal mode (fast transient response), while if the GM pin is set low, the auto

green mode is enabled.

The LD39130SJ (CSP version) always operates in auto green mode.

5.3

Input and output capacitors

The LD39130S requires external capacitors to ensure the regulator control loop stability.

These capacitors must be selected to meet the requirements of minimum capacitance and

equivalent series resistance (see Figure 32). Locating the input/output capacitors as close

as possible to the relative pins, is suggested.

5.3.1

Input capacitor

A capacitor with a minimum value of 1 µF is required at the input voltage of the LD39130S.

This capacitor must be located as close as possible to the input pin of the device and

returned to a clean analog ground. Any good quality ceramic capacitor can be used.

5.3.2

Output capacitor

The control loop of the LD39130S is designed to work with ceramic capacitors at the output.

The output capacitor must meet the requirements for the minimum amount of capacitance

and E.S.R. (equivalent series resistance) as shown in Figure 32.

The suggested value of 1 µF is a good choice to guarantee the stability of the regulator and

to provide the optimum transient response. The output capacitor must maintain its ESR and

capacitance in the stable region, over the full operating temperature range, to assure

stability.