0

0.2

0.4

0.6

0.8

1. 0

1. 2

1.4

TIME( 200Ps/DIV)

4.0

4.2

4.4

4.6

4.8

5.0

5.2

5.4

.

Control= 00 :)):00

3

VIN = 6V

I LOAD = 50 mA

15

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

7.3 Feature Description

7.3.1 Magnetic Boost DC-DC Converter

7.3.1.1 Boost Standby Mode

User can stop the boost converter operation by writing the Enables register bit EN_BOOST low. When

EN_BOOST is written high, the converter starts for 10 ms in PFM mode and then goes to PWM mode.

7.3.1.2 Boost Output Voltage Control

User can control the Boost output voltage by boost output 8-bit register.

BOOST OUTPUT [7:0] Register 0Fh

BOOST OUTPUT VOLTAGE (TYPICAL)

Bin

Hex

0000 0000

00

4 V

0000 0001

01

4.25 V

0000 0011

03

4.4 V

0000 0111

07

4.55 V

0000 1111

0F

4.7 V

0001 1111

1F

4.85 V

0011 1111

3F

5 V (default)

0111 1111

7F

5.15 V

1111 1111

FF

5.3 V

Figure 11. Boost Output Voltage Control

7.3.1.3 Boost Frequency Control

Register-frequency selections (address 10h). Register default value after reset is 07h.

FRQ_SEL[2:0]

FREQUENCY

1XX

2 MHz

01X

1.67 MHz

001

1 MHz

7.3.2 Functionality of RGB LED Outputs (R1-4, G1-4, B1-4)

The LP55281 device has 4 sets of RGB/color LED outputs. Each set has 3 outputs, which can be controlled

individually with a 6-bit PWM control register. The pulsed current level for each LED output is set with a single

external resistor RRGB and a 2-bit coarse adjustment bit for each LED output (see Table 1 and Table 2).