LP2980IM5X-3.3 Datasheet, PDF (10/25 Pages) Texas Instruments – Ultra Low Dropout Voltage, Output Voltage Accuracy 0.5% (A Grade)

LP2980-N
SNOS733M – APRIL 2000 – REVISED JUNE 2013
APPLICATION HINTS
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OUTPUT CAPACITOR
Like any low-dropout regulator, the LP2980-N requires an output capacitor to maintain regulator loop stability.
This capacitor must be selected to meet the requirements of minimum capacitance and equivalent series
resistance (ESR) range. It is not difficult to find capacitors which meet the criteria of the LP2980-N, as the
acceptable capacitance and ESR ranges are wider than for most other LDOs.
In general, the capacitor value must be at least 1 μF (over the actual ambient operating temperature), and the
ESR must be within the range indicated in Figure 34, Figure 35 and Figure 36. It should be noted that, although
a maximum ESR is shown in these Figures, it is very unlikely to find a capacitor with ESR that high.
Tantalum Capacitors
Surface-mountable solid tantalum capacitors offer a good combination of small physical size for the capacitance
value, and ESR in the range needed by the LP2980-N.
The results of testing the LP2980-N stability with surface-mount solid tantalum capacitors show good stability
with values of at least 1 μF. The value can be increased to 2.2 μF (or more) for even better performance,
including transient response and noise.
Small value tantalum capacitors that have been verified as suitable for use with the LP2980-N are shown in
Table 1. Capacitance values can be increased without limit.
Aluminum Electrolytic Capacitors
Although probably not a good choice for a production design, because of relatively large physical size, an
aluminum electrolytic capacitor can be used in the design prototype for an LP2980-N regulator. A value of at
least 1 μF should be used, and the ESR must meet the conditions of Figure 34, Figure 35 and Figure 36. If the
operating temperature drops below 0°C, the regulator may not remain stable, as the ESR of the aluminum
electrolytic capacitor will increase, and may exceed the limits indicated in the Figures.
Table 1. Surface-Mount Tantalum Capacitor
Selection Guide
1 μF Surface-Mount Tantalums
Manufacturer
Part Number
Kemet
T491A105M010AS
NEC
NRU105M10
Siemens
B45196-E3105-K
Nichicon
F931C105MA
Sprague
293D105X0016A2T
2.2 μF Surface-Mount Tantalums
Manufacturer
Part Number
Kemet
T491A225M010AS
NEC
NRU225M06
Siemens
B45196/2.2/10/10
Nichicon
F930J225MA
Sprague
293D225X0010A2T
Multilayer Ceramic Capacitors
Surface-mountable multilayer ceramic capacitors may be an attractive choice because of their relatively small
physical size and excellent RF characteristics. However, they sometimes have ESR values lower than the
minimum required by the LP2980-N, and relatively large capacitance change with temperature. The
manufacturer's datasheet for the capacitor should be consulted before selecting a value.
Test results of LP2980-N stability using multilayer ceramic capacitors show that a minimum value of 2.2 μF is
usually needed for the 5V regulator. For the lower output voltages, or for better performance, a higher value
should be used, such as 4.7 μF.
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