LP2975 Datasheet, PDF (9/37 Pages) National Semiconductor (TI) – MOSFET LDO Driver/Controller

LP2975
www.ti.com
SNVS006F – SEPTEMBER 1997 – REVISED APRIL 2013
REFERENCE DESIGNS
The LP2975 controller can be used with virtually any P-channel MOSFET to build a wide variety of linear voltage
regulators.
Since it would be impossible to document all the different voltage and current combinations that could be built, a
number of reference designs will be presented along with performance data for each.
THE PERFORMANCE DATA SHOWN IS ACTUAL TEST DATA, BUT IS NOT ENSURED. The following
reference designs have been confirmed with T_A = 25°C only, and no design consideration is given for operating
at any other ambient temperature.
DESIGN #1: V_OUT = 5V @ 5A
(Refer to TYPICAL APPLICATION CIRCUITS)
Components
C_IN = 82 µF Aluminum Electrolytic
C_OUT = 120 µF Aluminum Electrolytic
C_F = 220 pF
R_SC = 10 mΩ
P-FET = NDP6020P
Heatsink: (assuming V_IN ≤ 7V and T_A ≤ 60°C) if protection against a continuous short-circuit is required, a
heatsink with θ_S-A ≤ 1.5 °C/W must be used. However, if continuous short-circuit survivability is not needed, a
heatsink with θ_S-A ≤ 6 °C/W is adequate.
Performance Data
Dropout Voltage
Dropout voltage is defined as the minumum input-to-output differential voltage required by the regulator to keep
the output in regulation. It is measured by reducing V_IN until the output voltage drops below the nominal value
(the nominal value is the output voltage measured with V_IN = 5.5V). I_L = 5A for this test.
DROPOUT VOLTAGE = 323 mV
Load Regulation
Load regulation is defined as the maximum change in output voltage as the load current is varied. It is measured
by changing the load resistance and recording the minimum/maximum output voltage. The measured change in
output voltage is divided by the nominal output voltage and expressed as a percentage. V_IN = 5.6V for this test.
5 mA ≤ I_L ≤ 5A: LOAD REGULATION = 0.012%
0 ≤ I_L ≤ 5A: LOAD REGULATION = 0.135%
Line Regulation
Line regulation is defined as the maximum change in output voltage as the input voltage is varied. It is measured
by changing the input voltage and recording the minimum/maximum output voltage. The measured change in
output voltage is divided by the nominal output voltage and expressed as a percentage. I_L = 5A for this test.
5.4V ≤ V_IN ≤ 10V: LINE REGULATION = 0.03%
Output Noise Voltage
Output noise voltage was measured by connecting a wideband AC voltmeter (HP 400E) directly across the
output capacitor. V_IN = 6V and I_L = 5A for this test.
NOISE = 75 µV (rms)
Copyright © 1997–2013, Texas Instruments Incorporated
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