LP5569 datasheet(78/93 Pages) TI2

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LP5569

SNVSAP8A – JULY 2017 – REVISED SEPTEMBER 2017

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9 Application and Implementation

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 LP5569 device is designed as an autonomous lighting controller for handheld devices. In these devices,

extremely small form factor is needed; therefore, the LP5569 device is designed to require only four small

capacitors: input and output, as well as flying capacitor 1 and flying capacitor 2 for the charge pump. If the

system has other LED input voltages available, and the charge pump is not needed in the application, the

charge-pump capacitors can be omitted, thus reducing the solution even further. The device can drive RGB

LEDs or discrete LEDs of any color if desired.

9.2 Typical Applications

9.2.1 Single LP5569 Application

Figure 119 shows an example of a typical application that uses a charge pump to get high-enough voltage to

drive green and blue LEDs. Red LEDs are powered from VVIN for reduced power consumption. The device, with

a voltage range of 2.5 V to 4.5 V, is powered from three AA batteries, typically 3.6 V with 1.2-V cell voltage.

Design Requirements shows related design parameters for this example. In this example, input voltage with AA

batteries is typically over 3.6 V (cell voltage >1.2 V) for half of the battery lifetime. During this time the charge

pump operates in 1× mode, as the input voltage is enough for the green and blue LEDs. As the battery voltage

continues to decrease, the LP5569 device detects that the LED headroom voltage is too low and automatically

configures the charge pump to the 1.5× mode. In 1.5× mode, the LEDs can be powered with VIN down to 2.5 V,

where the batteries are almost empty.

LP5569 датащи(PDF) 78 Page - Texas Instruments