The LP2985-N is designed to work with ceramic capacitors on the output to take advantage of the benefits these capacitors offer. For capacitance values in the 2.2µF to 4.7µF range, ceramics are the least expensive and also have the lowest ESR values. Thus, these components are the most efficient at eliminating high-frequency noise. The ESR of a typical 2.2µF ceramic capacitor is in the range of 10mΩ to 20mΩ. This range easily meets the ESR limits required for stability by the LP2985-N.

One disadvantage of ceramic capacitors is that the capacitance varies with temperature. Most large-value ceramic capacitors (≥ 2.2µF) are manufactured with the Z5U or Y5V temperature characteristic. Thus, resulting in the capacitance dropping by more than 50% as the temperature goes from 25°C to 85°C.

This capacitance drop potentially cause problems if a 2.2µF capacitor is used on the output because that capacitor goes down to approximately 1µF at high ambient temperatures. Such low capacitance causes the LP2985-N to oscillate. If Z5U or Y5V capacitors are used on the output, adhere to a minimum capacitance value of 2.2µF.

A better choice for temperature coefficient in ceramic capacitors is X7R, which holds the capacitance within ±15%. Unfortunately, the larger values of capacitance are not offered by all manufacturers in the X7R dielectric.

Tantalum capacitors are less desirable than ceramics for use as output capacitors. These components are more expensive when comparing equivalent capacitance and voltage ratings in the 1µF to 4.7µF range.

Another important consideration is that tantalum capacitors have higher ESR values than equivalent size ceramics. Which means that although a tantalum capacitor potentially has an ESR value within the stable range, the capacitor is larger in capacitance. Thus, the tantalum capacitor is bigger and more costly than a ceramic capacitor with the same ESR value.

The ESR of a typical tantalum increases by approximately 2:1 as the temperature goes from 25°C down to –40°C, so some allow for guard band.