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LP5910

SNVSA91C – SEPTEMBER 2015 – REVISED JUNE 2016

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8.2.2.2 Input Capacitor

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

LP5910 IN pin to ground. (This capacitance value may be increased without limit.) The input 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.

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 guaranteed 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 1 µF

±30% over the entire operating temperature range.

8.2.2.3 Output Capacitor

For capacitance values in the range of 1 µF to 4.7 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 m

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

the LP5910. The temperature performance of ceramic capacitors varies by type. Most large value ceramic

capacitors (

≥ 2.2 µF) are manufactured with Z5U or Y5V temperature characteristics, which results in the

capacitance dropping by more than 50% as the temperature goes from 25°C to 85°C.

A better 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 4.7-µF range.

8.2.2.4 Capacitor Characteristics

The LP5910 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

requirement for stability for the LP5910.

A better 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. This means that while it may be possible to find a tantalum capacitor with an ESR value within the

stable range, it would have to be larger in capacitance (which means bigger and more costly) than a ceramic

capacitor with the same ESR value. Also, the ESR of a typical tantalum increases about 2:1 as the temperature

goes from 25°C down to –40°C, so some guard band must be allowed.

8.2.2.5 Remote Capacitor Operation

The LP5910 requires at least a 1-µF capacitor at the OUT pin, but there is no strict requirements about the

location of the capacitor in regards to the pin. In practical designs the output capacitor may be located up to

10 cm away from the LDO. This means that there is no need to have a special capacitor close to the OUT pin if

there is already respective capacitors in the system (like a capacitor at the input of supplied part). The remote

capacitor feature helps user to minimize the number of capacitors in the system.