LP2953_15 Datasheet, PDF (22/41 Pages) Texas Instruments – LP295x Adjustable Micropower Low-Dropout Voltage Regulators

LP2952-N, LP2952A, LP2953, LP2953A
SNVS095F – MAY 2004 – REVISED MARCH 2015
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Typical Applications (continued)
8.2.1.1 Design Requirements
For this design example, use the parameters listed in Table 1 as the input parameters.
DESIGN PARAMETER
Input voltage
Output voltage
Output current
RMS noise, 10 Hz to 100 kHz
PSRR at 1 kHz
Table 1. Design Parameters
DESIGN REQUIREMENT
6 V, ±10%, provided by the DC-DC converter switching at 1 MHz
5 V, ±1%
250 mA (maximum), 1 mA (minimum)
1 mV typical
50 dB typical
8.2.1.2 Detailed Design Procedure
At 150-mA loading, the dropout of the LP2952 and LP2953 has 600-mV maximum dropout over temperature —
thus, a 1500-mV headroom is sufficient for operation over both input and output voltage accuracy. The efficiency
of the LP2952 and LP2953 in this configuration is V_OUT / V_IN = 83.3%. Input and output capacitors are selected in
accordance with the External Capacitors section. Ceramic capacitances of 1 μF for the input and one 2.2-μF
capacitor for the output are selected. With an efficiency of 83.3% and a 250-mA maximum load, the internal
power dissipation is 250 mW, which corresponds to a 19.2°C junction temperature rise for the SOIC package.
With a V_IN – V_OUT differential of 1 V and a maximum load current of 250 mA the internal junction temperature (T_J)
of the SOIC package will rise 19.2°C above the ambient temperature. With an 85°C maximum ambient
temperature, the junction temperature is at 104.2°C. To minimize noise, a bypass capacitor of 100 pF is selected
between OUT and FEEDBACK pins.
8.2.1.3 Application Curves
Figure 34. Line Transient Response
Figure 35. Load Transient Response
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