LP5907 datasheet(15/50 Pages) TI2

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7.2.2.4 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. Connect at least a 1µF capacitor between the LP5907

input pin and ground for stable operation over the full load current range. Basically, having more output

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

The input capacitor must be located a distance of not more than 1cm 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 provide stable operation, good PCB practices must be used to minimize ground impedance and

to keep input inductance low. If these conditions cannot be met, or if long leads are used to connect

the battery or other power source to the LP5907, increase the input capacitor to at least 10µF. 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, verify by the manufacturer that the capacitor has a surge current rating sufficient for

the application. The initial tolerance, applied voltage derating, and temperature coefficient must all be

considered when selecting the input capacitor to make sure that the actual capacitance is never less

than 0.7µF over the entire operating range.

7.2.2.5 Output Capacitor

The LP5907 is designed specifically to work with a very small ceramic output capacitor, typically 1µF. A ceramic

capacitor (dielectric types X5R or X7R) in the 1µF to 10µF range, and with ESR between 5mΩ to 500mΩ, is

suitable in the LP5907 application circuit. For this device, connect the output capacitor 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 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 5mΩ to 500mΩ for stability. Like the input capacitor, the initial tolerance, applied

voltage derating, and temperature coefficient must all be considered when selecting the input capacitor to make

sure that the actual capacitance is never less than 0.7µF over the entire operating range.

7.2.2.6 Capacitor Characteristics

The LP5907 is designed to work with ceramic capacitors on the input and output to take advantage of the

benefits these components offer. For capacitance values in the range of 1µF to 10µF, 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 1µF ceramic capacitor is in the range of 20mΩ to 40mΩ, which easily meets the

ESR requirement for stability for the LP5907.

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 1µF to 10µF range.

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

ceramics. Which means that although a tantalum capacitor can possibly be found with an ESR value within

the stable range, the capacitor must be larger in capacitance (which means bigger and more costly) than a

ceramic capacitor with the same ESR value. The ESR of a typical tantalum increases by approximately 2:1 when

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

www.ti.com

LP5907

SNVS798Q – APRIL 2012 – REVISED JULY 2025

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