LR9500

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

5 of 6

www.unisonic.com.tw

QW-R102-083.a

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TYPICAL APPLICATION CIRCUIT

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EXTERNAL CAPACITORS

Like any low-dropout regulator, the LR9500 requires external capacitors for regulator stability. The LR9500 is

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

capacitors must be correctly selected for good performance.

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INPUT CAPACITOR

An input capacitor is required for stability. The input capacitor should be at least equal to or greater than the

output capacitor. It is recommended that a 0.47 µF capacitor be connected between the LR9500 input pin and

ground. 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.

Important

To ensure stable operation it is essential that good PCB practices are employed to minimize ground impedance

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

battery or other power source to the LR9500, then it is recommended to increase the input capacitor to at least 2.2

µF. Also, 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 ESR (Equivalent Series Resistance) on the input capacitor, but tolerance and

temperature coefficient must be considered when selecting the capacitor to ensure the capacitance will remain 0.47

μF ±30% over the entire operating temperature range.

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OUTPUT CAPACITOR

The LR9500 is designed specifically to work with very small ceramic output capacitors. A ceramic capacitor

(dielectric types X5R or X7R) in the 0.47 μF to 10 μF range, and with ESR between 5 mΩ to 500 mΩ, is suitable in

good ground connection and should be mounted within 1 cm of the device.

attractive for reasons of size and cost (see the CAPACITOR CHARACTERISTICS section below).

The output capacitor must meet the requirement for the minimum value of capacitance and have an ESR value

that is within the range 5 mΩ to 500 mΩ for stability.