8.2.2 Detailed Design Procedure

8.2.2.1 External Capacitors

As with most low-dropout regulators, the LP5912-EP requires external capacitors for regulator stability. The

device is specifically designed for portable applications requiring minimum board space and the smallest

possible components. These capacitors must be correctly selected for good performance.

8.2.2.2 Input Capacitor

An input capacitor is required for stability. The input capacitor must be at least equal to, or greater than, the

output capacitor for good load-transient performance. A capacitor of at least 1 µF must be connected between

the LP5912-EP IN pin and ground for stable operation over full load-current range. Having more output than

input capacitance is acceptable, as long as the input is at least 1 µF.

The input capacitor must be located no more than 1 cm from the input pin and returned to a clean analog

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

Note

To ensure stable operation, good PCB practices must be employed to minimize ground impedance

and keep input inductance low. If these conditions cannot be met, or if long leads connect the

battery or other power source to the LP5912-EP, increase the value of the input capacitor to at least

10 µF. Also, tantalum capacitors can suffer catastrophic failures resulting from surge current when

connected to a low-impedance source of power (such as a battery or a very large capacitor). If a

tantalum capacitor is used at the input, the capacitor must be verified by the manufacturer to have

a surge current rating sufficient for the application. There are no requirements for the equivalent

series resistance (ESR) on the input capacitor, but tolerance and temperature coefficient must be

considered when selecting the capacitor to ensure the capacitance remains at 1 μF ±30% over the

entire operating temperature range.

8.2.2.3 Output Capacitor

The LP5912-EP is designed specifically to work with a very small ceramic output capacitor, typically 1 µF. Use

a ceramic capacitor (dielectric types of X5R or X7R) in the 1-µF to 10-µF range, and with an ESR from 5 mΩ to

500 mΩ, in the LP5912-EP application circuit. For this device, the output capacitor must be connected between

the OUT pin with a good connection back to the GND pin.

Tantalum or film capacitors can also be used at the device output, VOUT, but these components are not as

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

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

that is within the range of 5 mΩ to 500 mΩ for stability.

8.2.2.4 Capacitor Characteristics

The LP5912-EP is designed to work with ceramic capacitors on the input and output to take advantage of the

benefits they offer. For capacitance values in the range of 1 µF to 10 µF, ceramic capacitors are the smallest,

least expensive, and have the lowest ESR values, thus making them best for eliminating high-frequency noise.

The ESR of a typical 1-µF ceramic capacitor is in the range of 20 mΩ to 40 mΩ, which easily meets the ESR

stability requirement for the LP5912-EP.

The preferred choice for temperature coefficient in a ceramic capacitor is X7R. This type of capacitor is the

most stable and holds the capacitance within ±15% over the temperature range. Tantalum capacitors are

less desirable than ceramic for use as output capacitors because they are more expensive when comparing

equivalent capacitance and voltage ratings in the 1-µF to 10-µF range.

Another important consideration is that tantalum capacitors have higher ESR values than equivalent size

ceramics. Although a tantalum capacitor can possibly be found with an ESR value within the stable range,

low ESR tantalum capacitors are offered with larger capacitance (which means bigger and more costly) than a

LP5912-EP

SNVSC57 – SEPTEMBER 2022

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