LP2982 Datasheet, PDF (15/28 Pages) National Semiconductor (TI) – Micropower 50 mA Ultra Low-Dropout Regulator

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8 Application and Implementation
LP2982
SNVS128K – MARCH 2000 – REVISED JUNE 2016
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 LP2982 is a linear voltage regulator operating from 2.1 V to 16 V on the input and regulates voltages
between 3 V to 5 V with 1% accuracy and 50-mA maximum output current. Efficiency is defined by the ratio of
output voltage to input voltage because the LP2982 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, power supply rejection ratio (PSRR), or any other
transient specification is required, then the design becomes more challenging.
8.2 Typical Application
V_IN
IN
C_IN
1 µF
OUT
V_OUT
C_OUT (Tantalum)
2.2 µF (5-V device)
4.7 µF (3-V and 3.3-V devices)
ON/OFF
ON
OFF
ON/OFF BYPASS
GND
C_BYPASS
0.01 µF
ON/OFF input must be actively terminated. Tie to V_IN if this function is not to be used.
Minimum output capacitance is shown to insure stability over full load current range. More capacitance provides
superior dynamic performance and additional stability margin (see Capacitor Characteristics).
Figure 36. LP2982 Typical Application
8.2.1 Design Requirements
PARAMETER
Input voltage
Output voltage
Output current
Ambient temperature
DESIGN REQUIREMENT
5 V ±10%
3.3 V ±3.5%
50 mA
85°C
8.2.2 Detailed Design Procedure
8.2.2.1 External Capacitors
Like any low-dropout regulator, the external capacitors used with the LP2982 must be carefully selected to
assure regulator loop stability.
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