0.0

100.0

200.0

300.0

400.0

500.0

TIME (é

s)

5.1

4.8

4.4

4.1

3.7

3.4

VOUT TARGET VALUE = 5V

VIN = 3.6V

5.1

4.8

4.4

4.1

3.7

3.4

TIME (100 é

s/DIV)

ILOAD = 50 mA

VIN = 3.0V TO 3.6V

VOUT = 5V (10 mV/DIV)

VIN = 1V/DIV

TIME (200 ns/DIV)

33

LP55281

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SNVS458D – JUNE 2007 – REVISED OCTOBER 2016

Product Folder Links: LP55281

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Copyright © 2007–2016, Texas Instruments Incorporated

8.2.2.1.4

Output Diode, D1

A Schottky diode must be used for the output diode. To maintain high efficiency the average current rating of the

Schottky diode must be larger than the peak inductor current (1 A). Schottky diodes with a low forward drop and

fast switching speeds are ideal for increasing efficiency in portable applications. Choose a reverse breakdown of

the Schottky diode larger than the output voltage. Do not use ordinary rectifier diodes, since slow switching

speeds and long recovery times cause the efficiency and the load regulation to suffer.

8.2.2.1.5

Inductor, L

The high switching frequency of the LP55281 device enables the use of the small surface mount inductor. A 4.7-

µH shielded inductor is suggested for 2-MHz operation, use 10 µH at 1 MHz. The inductor should have a

saturation current rating higher than the peak current it will experience during circuit operation (approximately 1

A). Less than 300-m

Ω ESR is suggested for high efficiency. Open core inductors cause flux linkage with circuit

components and interfere with the normal operation of the circuit. This should be avoided. For high efficiency,

choose an inductor with a high frequency core material such as ferrite to reduce the core losses. To minimize

radiated noise, use a toroid, pot core or shielded core inductor. TI recommends inductors LPS3015 and LPS4012

from Coilcraft and VLF4012 from TDK.

8.2.3 Application Curves

Figure 27. Boost Typical Waveforms With 100 mA Load

Figure 28. Boost Line Regulation

Figure 29. Boost Start-up With No Load

50 - 100 mA

Figure 30. Boost Load Regulation