LP2989 Datasheet, PDF (16/34 Pages) National Semiconductor (TI) – Micropower/Low Noise, 500 mA Ultra Low-Dropout Regulator For Use with Ceramic Output Capacitors

LP2989
SNVS083O – FEBRUARY 2005 – REVISED MARCH 2015
8 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LP2989 is a linear voltage regulator operating from 2.1 V to 16 V on the input and regulates voltages
between 2.5 V to 5 V with 0.75% accuracy and 500 mA maximum outputs current. Efficiency is defined by the
ratio of output voltage to input voltage because the LP2989 is a linear voltage regulator. To achieve high
efficiency, the dropout voltage (V_IN – V_OUT) must be as small as possible, thus requiring a very low dropout LDO.
Successfully implementing an LDO in an application depends on the application requirements. If the
requirements are simply input voltage and output voltage, compliance specifications (such as internal power
dissipation or stability) must be verified to ensure a solid design. If timing, start-up, noise, PSRR, or any other
transient specification is required, the design becomes more challenging. This section discusses the
implementation and behavior of the LP2989 LDO.
8.2 Typical Application
*Capacitance values shown are minimum required to assure stability, but may be increased without limit. Larger
output capacitor provides improved dynamic response. See the Output Capacitor section.
**Shutdown must be actively terminated (see the Shutdown Input Operation section). Tie to IN (pin 4) if not use.
Figure 40. Typical Application Schematic
8.2.1 Design Requirements
DESIGN PARAMETER
Input voltage
Output voltage
Output current
RMS noise, 100 Hz to 100 kHz
PSRR at 1 kHz
DESIGN REQUIREMENT
6.5 V, ±10%,
5 V, ±1%
500 mA (maximum), 1 mA (minimum)
18 μV_RMS typical
60 dB typical
16
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