LP2975 datasheet(13/37 Pages) TI1

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LP2975

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SNVS006F – SEPTEMBER 1997 – REVISED APRIL 2013

DESIGN #3: VOUT = 1.5V @ 6A.

(Refer to TYPICAL APPLICATION CIRCUITS, Adjustable Voltage Regulator)

Components

CIN = 1000 µF Aluminum Electrolytic

COUT = 4 X 330 µF OSCON Aluminum Electrolytic

CC = NOT USED

R1 = 261

Ω, 1%

R2 = 1.21 k

Ω, 1%

RSC = 6 mΩ

P-FET = NDP6020P

Heatsink: (Assuming VIN ≤ 3.3V and TA ≤ 60°C) if protection against a continuous short-circuit is required, a

heatsink with

θS-A < 2.5 °C/W must be used. However, if continuous short-circuit survivability is not needed, a

heatsink with

θS-A < 7 °C/W is adequate.

Performance Data

Dropout Voltage

Dropout voltage is defined as the minimum input-to-output differential voltage required by the regulator to keep

the output in regulation. It is measured by reducing VIN until the output voltage drops below the nominal value

(the nominal value is the output voltage measured with VIN = 3.3V). IL = 6A for this test.

DROPOUT VOLTAGE = 0.68V

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. VIN = 3.3V for this test.

≤ IL ≤ 6A: LOAD REGULATION = 0.092%

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. IL = 6A for this test.

3.3V

≤ VIN ≤ 5V: LINE REGULATION = 0.033%

Output Noise Voltage

Output noise voltage was measured by connecting a wideband AC voltmeter (HP 400E) directly across the

output capacitor. VIN = 3.3V and IL = 6A for this test.

NOISE = 60 µV (rms)

Transient Response

Transient response is defined as the change in output voltage which occurs after the load current is suddenly

changed. VIN = 3.3V for this test.

The load resistor is connected to the regulator output using a switch so that the load current increases from 0 to

6A abruptly. The change in output voltage is shown in the scope photo (the vertical scale is 50 mV/division and

the horizontal scale is 20 µs/division. The regulator nominal output (1.5V) is located on the center line of the

photo. A maximum change of about

−80 mV is shown.

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