LP5952

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SNVS469F – OCTOBER 2006 – REVISED DECEMBER 2015

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

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

A capacitor at VBATT is not required if the distance to the supply does not exceed 5 cm.

If the device is used in the typical application as post regulator after a DC-DC regulator, no input capacitors are

required — the capacitors of the DC-DC regulator (CIN and COUT) are sufficient if both components are mounted

close to each other and a proper GND plane is used. If the distance between the output capacitor of the DC-DC

regulator and the IN pin of the LP5952 is larger than 5 cm, adding an input capacitor at VIN is recommended.

NOTE

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.

The equivalent series resistance (ESR) of the input capacitor should be in the range of 3 m

Ω to 300 mΩ. The

tolerance and temperature coefficient must be considered when selecting the capacitor to ensure the

capacitance remains

≥ 470 nF over the entire operating temperature range.

8.2.1.2.3

Output Capacitor

The LP5952 is designed specifically to work with very small ceramic output capacitors. A ceramic capacitor

(dielectric types X7R, Z5U, or Y5V) in the 2.2-µF range (up to 10 µF) and with an ESR between 3 m

Ω to 300 mΩ

is suitable as COUT in the LP5952 application circuit.

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

analog ground.

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

reasons of size and cost (see Capacitor Characteristics).

8.2.1.2.4

Capacitor Characteristics

The LP5952 is designed to work with ceramic capacitors on the output to take advantage of the benefits they

offer. For capacitance values in the 1-µF to 4.7-µF range, 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 3 m

Ω to 40 mΩ, which easily meets the ESR requirement for

stability for the LP5952.

For both input and output capacitors, careful interpretation of the capacitor specification is required to ensure

correct device operation. The capacitor value can change greatly, depending on the operating conditions and

capacitor type.

In particular, the output capacitor selection must take account of all the capacitor parameters, to ensure that the

specification is met within the application. The capacitance can vary with DC bias conditions as well as

temperature and frequency of operation. Capacitor values show some decrease over time due to aging. The

capacitor parameters are also dependant on the particular case size, with smaller sizes giving poorer

performance figures in general. Figure 10 shows a typical graph comparing different capacitor case sizes in a

capacitance vs. DC Bias plot. As shown Figure 10, increasing the DC-bias condition can result in the capacitance

value falling below the minimum value given in Input and Output Capacitors (Recommended) (0.47 µF or 1.5 µF

in this case). The graph shows the capacitance out of specification for the 0402 case size capacitor at higher

bias voltages. It is therefore recommended that the capacitor-manufacturer specifications for the nominal value

capacitor are consulted for all conditions, as some capacitor sizes (such as 0402) may not be suitable in the

actual application.

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