LP2980-N

SNOS733M – APRIL 2000 – REVISED JUNE 2013

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APPLICATION HINTS

OUTPUT CAPACITOR

Like any low-dropout regulator, the LP2980-N requires an output capacitor to maintain regulator loop stability.

This capacitor must be selected to meet the requirements of minimum capacitance and equivalent series

resistance (ESR) range. It is not difficult to find capacitors which meet the criteria of the LP2980-N, as the

acceptable capacitance and ESR ranges are wider than for most other LDOs.

In general, the capacitor value must be at least 1

μF (over the actual ambient operating temperature), and the

ESR must be within the range indicated in Figure 34, Figure 35 and Figure 36. It should be noted that, although

a maximum ESR is shown in these Figures, it is very unlikely to find a capacitor with ESR that high.

Tantalum Capacitors

Surface-mountable solid tantalum capacitors offer a good combination of small physical size for the capacitance

value, and ESR in the range needed by the LP2980-N.

The results of testing the LP2980-N stability with surface-mount solid tantalum capacitors show good stability

with values of at least 1

μF. The value can be increased to 2.2 μF (or more) for even better performance,

including transient response and noise.

Small value tantalum capacitors that have been verified as suitable for use with the LP2980-N are shown in

Table 1. Capacitance values can be increased without limit.

Aluminum Electrolytic Capacitors

Although probably not a good choice for a production design, because of relatively large physical size, an

aluminum electrolytic capacitor can be used in the design prototype for an LP2980-N regulator. A value of at

least 1

μF should be used, and the ESR must meet the conditions of Figure 34, Figure 35 and Figure 36. If the

operating temperature drops below 0°C, the regulator may not remain stable, as the ESR of the aluminum

electrolytic capacitor will increase, and may exceed the limits indicated in the Figures.

Table 1. Surface-Mount Tantalum Capacitor

Selection Guide

1

μF Surface-Mount Tantalums

Manufacturer

Part Number

Kemet

T491A105M010AS

NEC

NRU105M10

Siemens

B45196-E3105-K

Nichicon

F931C105MA

Sprague

293D105X0016A2T

2.2

μF Surface-Mount Tantalums

Manufacturer

Part Number

Kemet

T491A225M010AS

NEC

NRU225M06

Siemens

B45196/2.2/10/10

Nichicon

F930J225MA

Sprague

293D225X0010A2T

Multilayer Ceramic Capacitors

Surface-mountable multilayer ceramic capacitors may be an attractive choice because of their relatively small

physical size and excellent RF characteristics. However, they sometimes have ESR values lower than the

minimum required by the LP2980-N, and relatively large capacitance change with temperature. The

manufacturer's datasheet for the capacitor should be consulted before selecting a value.

Test results of LP2980-N stability using multilayer ceramic capacitors show that a minimum value of 2.2

μF is

usually needed for the 5V regulator. For the lower output voltages, or for better performance, a higher value

should be used, such as 4.7

μF.

10

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