LP2985-N_15 Datasheet, PDF (15/41 Pages) Texas Instruments – LP2985-N Micropower 150-mA Low-Noise Ultra-Low-Dropout Regulator in SOT-23 and DSBGA Packages Designed for Use with Very Low ESR Output Capacitors

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9 Application and Implementation
LP2985-N
SNVS018X – MARCH 2000 – REVISED MAY 2015
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.
9.1 Application Information
The LP2985-N is a linear voltage regulator operating from 2.5 V to 16 V on the input and regulates voltages
between 2.5 V to 6.1 V with 1% accuracy and 150-mA maximum output current. Efficiency is defined by the ratio
of output voltage to input voltage because the LP2985-N 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.
9.2 Typical Application
*ON/OFF input must be actively terminated. Tie to V_IN if this function is not to be used.
**Minimum capacitance is shown to ensure stability (may be increased without limit). Ceramic capacitor required for
output (see Output Capacitor).
***Reduces output noise (may be omitted if application is not noise critical). Use ceramic or film type with very low
leakage current (see Noise Bypass Capacitor).
Figure 21. Typical Application Schematic
9.2.1 Design Requirements
DESIGN PARAMETERS
Input voltage
Output voltage
Output current
RMS noise, 300 Hz to 50 kHz
PSRR at 1 kHz
VALUE
4.3 V, ±10% provided by the DC-DC converter switching at 1 MHz
3.3 V, ±5%
150 mA (maximum), 1 mA (minimum)
< 50 µV_RMS
> 40 dB
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