Preferably, use ceramic capacitors on the output of the LP2985 for several reasons. For capacitances ranging from 2.2μF to 4.7μF, ceramic capacitors have the lowest cost and lowest ESR, making these components choice candidates for filtering high-frequency noise. For instance, a typical 2.2μF ceramic capacitor has an ESR ranging from 10mΩ to 20mΩ, which satisfies the minimum ESR requirements of the regulator. Ceramic capacitors have one major disadvantage to be taken into account: a poor temperature coefficient, where the capacitance varies significantly with temperature. For instance, a large-value ceramic capacitor (≥ 2.2μF) potentially loses more than half of the capacitance as the temperature rises from 25°C to 85°C. Thus, a 2.2μF capacitor at 25°C drops well below the minimum C_OUT required for stability, as ambient temperature rises. For this reason, select an output capacitor that maintains the minimum 2.2μF required for stability over the entire operating temperature range. There are some ceramic capacitors that maintain a ±15% capacitance tolerance over temperature.

Tantalum capacitors are able to be used at the output of the LP2985, but there are significant disadvantages prohibiting this usage:

• In the 1μF to 4.7μF range, tantalum capacitors are more expensive than ceramics of the equivalent capacitance and voltage ratings.
• Tantalum capacitors have higher ESR values than equivalent-sized ceramic counterparts. Thus, to meet the ESR requirements, a higher-capacitance tantalum is required, at the expense of larger size and higher cost.
• The ESR of a tantalum capacitor increases as temperature drops, as much as double from +25°C to –40°C. Thus, maintain ESR margins over the temperature range to prevent regulator instability.