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LP8900

SNVS542E – MAY 2008 – REVISED JUNE 2016

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Typical Application (continued)

9.2.1 Design Requirements

Some of the design requirements for this dual linear regulator include:

Table 1. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

Minimum input voltage

1.8 V

Minimum output voltage

1.2 V

Output current

200 mA/Channel

(1)

Typical values apply for TA = 25°C; minimim and maximum values apply over the full junction temperature range for operation, −40 to

+125°C, unless otherwise specified.

(2)

The capacitor tolerance should be 30% or better over temperature. The full operating conditions for the application should be considered

when selecting a suitable capacitor to ensure that the minimum value of capacitance is always met. Recommended capacitor type is

X7R or X5R. (See External Capacitors.)

Table 2. Recommended Capacitor Specifications

PARAMETER

TEST CONDITIONS

MIN(1)

TYP(1)

MAX(1)

UNIT

CIN

Input capacitor

Capacitance(2)

0.33

1

10

µF

COUT

Output capacitor

0.33

1

4.7

µF

ESR

5

500

m

Ω

9.2.2 Detailed Design Procedure

9.2.2.1 External Capacitors

In common with most regulators, the LP8900 requires external capacitors for regulator stability. The LP8900 is

specifically designed for portable applications requiring minimum board space and smallest components. These

capacitors must be correctly selected for good performance.

9.2.2.2 Input Capacitor

An input capacitor is required for stability. It is recommended that a 1-µF capacitor be connected between the

LP8900 IN pin and ground. (This capacitance value may be increased to 10 µF.)

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.

NOTE

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 equivalent series resistance (ESR) on the input capacitor, but tolerance,

temperature, and voltage coefficients must be considered when selecting the capacitor to ensure the capacitance

remains

≊ 1 µF over the entire operating temperature range.

9.2.2.3 Output Capacitor

Correct selection of the output capacitor is critical to ensure stable operation in the intended application.

The output capacitor must meet all the requirements specified in the recommended capacitor table over all

conditions in the application. These conditions include DC bias, frequency and temperature. Unstable operation

results if the capacitance drops below the minimum specified value.

The LP8900 is designed specifically to work with very small ceramic output capacitors. A 1-µF ceramic capacitor

(dielectric type X7R or X5R) with an ESR between 5 m

Ω to 500 mΩ, is suitable in the LP8900 application circuit.