LP3996

SNVS360D – NOVEMBER 2006 – REVISED OCTOBER 2013

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APPLICATION HINTS

Operation Description

The LP3996 is a low quiescent current, power management IC, designed specifically for portable applications

requiring minimum board space and smallest components. The LP3996 contains two independently selectable

LDOs. The first is capable of sourcing 150 mA at outputs between 0.8V and 3.3V. The second can source 300

mA at an output voltage of 0.8V to 3.3V. In addition, LDO2 contains power good flag circuit, which monitors the

output voltage and indicates when it is within 8% of its nominal value. The flag will also act as a power-on-reset

signal and, by adding an external capacitor; a delay may be programmed for the POR output.

Input Capacitor

An input capacitor is required for stability. It is recommended that a 1.0 µF capacitor be connected between the

LP3996 input pin and ground (this capacitance value may be increased without limit).

This capacitor must be located a distance of not more than 1 cm from the input pin and returned to a clean

analogue ground. Any good quality ceramic, tantalum, or film capacitor may be used at the input.

Important: Tantalum capacitors can suffer catastrophic failures due to surge current when connected to a low-

impedance source of power (like a battery or a very large capacitor). If a tantalum capacitor is used at the input,

it must be ensured by the manufacturer to have a surge current rating sufficient for the application.

There are no requirements for the ESR (Equivalent Series Resistance) on the input capacitor, but tolerance and

temperature coefficient must be considered when selecting the capacitor to ensure the capacitance will remain

approximately 1.0 µF over the entire operating temperature range.

Output Capacitor

The LP3996 is designed specifically to work with very small ceramic output capacitors. A 1.0 µF ceramic

capacitor (temperature types Z5U, Y5V or X7R) with ESR between 5 m

Ω to 500 mΩ, is suitable in the LP3996

application circuit.

For this device the output capacitor should be connected between the VOUT pin and ground.

It is also possible to use tantalum or film capacitors at the device output, COUT (or VOUT), but these are not as

attractive for reasons of size and cost (see Capacitor Characteristics).

The output capacitor must meet the requirement for the minimum value of capacitance and also have an ESR

value that is within the range 5 m

Ω to 500 mΩ for stability.

No-Load Stability

The LP3996 will remain stable and in regulation with no external load. This is an important consideration in some

circuits, for example CMOS RAM keep-alive applications.

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