Datasheet

LM26480
www.ti.com
SNVS543I JANUARY 2008REVISED MAY 2013
LDO Dapacitor Selection
Input Capacitor
An input capacitor is required for stability. It is recommended that a 1.0 μF capacitor be connected between the
LDO input pin and ground (this capacitance value may be increased without limit). This capacitor must be located
a distance of not more than 1 cm from the input pin and returned to a clean analog ground. Any good quality
ceramic, tantalum, or film capacitor may be used at the input.
WARNING
Important: Tantalum capacitors can suffer catastrophic failures due to surge
currents 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
specified by the manufacturer to have a surge current rating sufficient for the
application.
There are no requirements for the ESR on the input capacitor, but tolerance and
temperature coefficient must be considered when selecting the capacitor to
ensure the capacitance will remain approximately 1.0 μF over the entire
operating temperature range.
Output Capacitor
The LDOs on the LM26480 are designed specifically to work with very small ceramic output capacitors. A 1.0 μF
ceramic capacitor (temperature types Z5U, Y5V or X7R) with ESR between 5 m to 500 m, are suitable in the
application circuit. It is also possible to use tantalum or film capacitors at the device output COUT (or VOUT), but
these are not as attractive for reasons of size and cost. The output capacitor must meet the requirement for the
minimum value of capacitance and also have an ESR value that is within the range 5 m to 500 m for stability.
Capacitor Characteristics
The LDOs are designed to work with ceramic capacitors on the output to take advantage of the benefits they
offer. For capacitance values in the range of 0.47 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 1.0 μF ceramic capacitor is in the range of 20 m to 40 m, which easily meets the ESR
requirement for stability for the LDOs.
For both input and output capacitors, careful interpretation of the capacitor specification is required to ensure
correct device operation. The capacitor value can change greatly, depending on the operating conditions and
capacitor type.
In particular, the output capacitor selection should take account of all the capacitor parameters, to ensure that the
specification is met within the application. The capacitance can vary with DC bias conditions as well as
temperature and frequency of operation. Capacitor values will also show some decrease over time due to aging.
The capacitor parameters are also dependent on the particular case size, with smaller sizes giving poorer
performance figures in general. As an example, the graph below shows a typical graph comparing different
capacitor case sizes in a capacitance vs. DC bias plot.
Copyright © 2008–2013, Texas Instruments Incorporated Submit Documentation Feedback 27
Product Folder Links: LM26480