LP2986ILD-3.3 Datasheet, PDF (12/26 Pages) Texas Instruments – Micropower, 200 mA Ultra Low-Dropout Fixed or Adjustable Voltage Regulator

LP2986
SNVS137H – MARCH 1999 – REVISED APRIL 2013
APPLICATION HINTS
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WSON PACKAGE DEVICES
The LP2986 is offered in the 8 lead WSON surface mount package to allow for increased power dissipation
compared to the SOIC-8 and VSSOP-8. For details on WSON thermal performance as well as mounting and
soldering specifications, refer to the WSON MOUNTING section.
EXTERNAL CAPACITORS
Like any low-dropout regulator, external capacitors are required to assure stability. These capacitors must be
correctly selected for proper performance.
INPUT CAPACITOR: An input capacitor (≥ 2.2 µF) is required between the LP2986 input and ground (amount of
capacitance may be increased without limit).
This capacitor must be located a distance of not more than 0.5” from the input pin and returned to a clean analog
ground. Any good quality ceramic or tantalum may be used for this capacitor.
OUTPUT CAPACITOR: The output capacitor must meet the requirement for minimum amount of capacitance
and also have an appropriate E.S.R. (equivalent series resistance) value.
Curves are provided which show the allowable ESR range as a function of load current for various output
voltages and capacitor values (see ESR curves below).
Figure 34. ESR Curves For 5V Output
Figure 35. ESR Curves For 2.5V Output
IMPORTANT: The output capacitor must maintain its ESR in the stable region over the full operating temperature
range of the application to assure stability.
The minimum required amount of output capacitance is 4.7 µF. Output capacitor size can be increased without
limit.
It is important to remember that capacitor tolerance and variation with temperature must be taken into
consideration when selecting an output capacitor so that the minimum required amount of output capacitance is
provided over the full operating temperature range. A good Tantalum capacitor will show very little variation with
temperature, but a ceramic may not be as good (see next section).
CAPACITOR CHARACTERISTICS
TANTALUM: The best choice for size, cost, and performance are solid tantalum capacitors. Available from many
sources, their typical ESR is very close to the ideal value required on the output of many LDO regulators.
Tantalums also have good temperature stability: a 4.7 µF was tested and showed only a 10% decline in
capacitance as the temperature was decreased from +125°C to −40°C. The ESR increased only about 2:1 over
the same range of temperature.
However, it should be noted that the increasing ESR at lower temperatures present in all tantalums can cause
oscillations when marginal quality capacitors are used (where the ESR of the capacitor is near the upper limit of
the stability range at room temperature).
CERAMIC: For a given amount of a capacitance, ceramics are usually larger and more costly than tantalums.
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