SNVS458D June   2007  – October 2016 LP55281

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 SPI Timing Requirements
    7. 6.7 I2C Timing Requirements
    8. 6.8 Boost Converter Typical Characteristics
    9. 6.9 RGB Driver Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Magnetic Boost DC-DC Converter
        1. 7.3.1.1 Boost Standby Mode
        2. 7.3.1.2 Boost Output Voltage Control
        3. 7.3.1.3 Boost Frequency Control
      2. 7.3.2 Functionality of RGB LED Outputs (R1-4, G1-4, B1-4)
        1. 7.3.2.1 PWM Control Timing
      3. 7.3.3 Audio Synchronization
        1. 7.3.3.1 Control of Audio Synchronization
        2. 7.3.3.2 ALED Driver
          1. 7.3.3.2.1 Adjustment of ALED Driver
      4. 7.3.4 LED Test Interface
        1. 7.3.4.1 LED Test Procedure
        2. 7.3.4.2 LED Test Time Estimation
      5. 7.3.5 7-V Shielding
    4. 7.4 Device Functional Modes
      1. 7.4.1 Modes Of Operation
    5. 7.5 Programming
      1. 7.5.1 SPI Interface
      2. 7.5.2 I2C Compatible Serial Bus Interface
        1. 7.5.2.1 Interface Bus Overview
        2. 7.5.2.2 Data Transactions
        3. 7.5.2.3 Acknowledge Cycle
        4. 7.5.2.4 Acknowledge After Every Byte Rule
        5. 7.5.2.5 Addressing Transfer Formats
        6. 7.5.2.6 Control Register Write Cycle
        7. 7.5.2.7 Control Register Read Cycle
    6. 7.6 Register Maps
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Recommended External Components
          1. 8.2.2.1.1 Output Capacitor, COUT
          2. 8.2.2.1.2 List Of Recommended External Components
          3. 8.2.2.1.3 Input Capacitor, CIN
          4. 8.2.2.1.4 Output Diode, D1
          5. 8.2.2.1.5 Inductor, L
      3. 8.2.3 Application Curves
    3. 8.3 Initialization Set Up Example
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Boost Output Capacitor Placement
      2. 10.1.2 Schottky Diode Placement
      3. 10.1.3 Inductor Placement
      4. 10.1.4 Boost Input Capacitor Placement
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ(パッケージ|ピン)
サーマルパッド・メカニカル・データ
発注情報

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.

Application Information

The LP55281 quadruple RGB driver with integrated boost converter provides a complete solution for driving up to 12 LEDs via either I2C or SPI interface.

Typical Application

LP55281 20201101.gif Figure 26. LP55281 Typical Application

Design Requirements

For typical LED-driver applications, use the parameters listed in Table 10.

Table 10. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
Input voltage 3 V
Output voltage 5 V
SW pin current limit 550 mA (minimum)
Efficiency 75%

Detailed Design Procedure

The output current can be approximated by using this formula: IOUT = (VIN × ISW_MAX × efficiency) / VOUT.

Example: 3 V × 550 mA × 0.75 / 5 V = 248 mA

Recommended External Components

Output Capacitor, COUT

The output capacitor COUT directly affects the magnitude of the output ripple voltage. In general, the higher the value of COUT, the lower the output ripple magnitude. Multilayer ceramic capacitors with low ESR are the best choice. At the lighter loads, the low ESR ceramics offer a much lower VOUT ripple than the higher ESR tantalums of the same value. At the higher loads, the ceramics offer a slightly lower VOUT ripple magnitude than the tantalums of the same value. However, the dv/dt of the VOUT ripple with the ceramics is much lower than the tantalums under all load conditions. Capacitor voltage rating must be sufficient, TI recommends 10 V or greater.

Some ceramic capacitors, especially those in small packages, exhibit a strong capacitance reduction with the increased applied voltage. The capacitance value can fall to below half of the nominal capacitance. Output capacitance that is too low increase the noise, and it can make the boost converter unstable.

List Of Recommended External Components

PARAMETER VALUE UNIT TYPE
CVDD1 C between VDD1 and GND 100 nF Ceramic, X7R/X5R
CVDD2 C between VDD2 and GND 100 nF Ceramic, X7R/X5R
CVDDIO C between VDDIO and GND 100 nF Ceramic, X7R/X5R
CVDDA C between VDDA and GND 1 µF Ceramic, X7R/X5R
COUT C between FB and GND 10 µF Ceramic, X7R/X5R
CIN C between battery voltage and GND 10 µF Ceramic, X7R/X5R
LBOOST L between SW and VBAT at 2 MHz 4.7 µH Shielded, low ESR, ISAT 1A
CVREF C between VREF and GND 100 nF Ceramic, X7R
CVDDIO C between VDDIO and GND 100 nF Ceramic, X7R
RRGB R between IRGB and GND 8.2 ±1%
RRT R between IRT and GND 82 ±1%
D1 Rectifying Diode (Vf at maxload) 0.3 V Schottky diode
CASE C between Audio input and ASEx 100 nF Ceramic, X7R/X5R
LEDs User defined

Input Capacitor, CIN

The input capacitor CIN directly affects the magnitude of the input ripple voltage and to a lesser degree the VOUT ripple. A higher value CIN gives a lower VIN ripple. Capacitor voltage rating must be sufficient, TI recommends 10 V or greater.

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.

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-mΩ 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.

Application Curves

LP55281 20201108.gif
Figure 27. Boost Typical Waveforms With 100 mA Load
LP55281 20201112.gif
Figure 29. Boost Start-up With No Load
LP55281 20201116.gif
Figure 31. Efficiency at Low Load vs Autoload
LP55281 20201111.gif
Figure 28. Boost Line Regulation
LP55281 20201113.png
50 - 100 mA
Figure 30. Boost Load Regulation

Initialization Set Up Example

The following table gives an example initialization sequence to illustrate the various LED and Boost configuration options. Not every feature of the LP55281 is configured in this example.

Table 11. Initialization Example

ADDRESS DATA REGISTER COMMENT
60h 00h RESET Execute software reset to initialize LP55281
00h 3Fh RED 1 IPLS = 0 (25% IRGB), PWM = 100%
01h 5Fh GREEN1 IPLS = 1 (50% IRGB), PWM = 50%
02h 90h BLUE1 IPLS = 2 (75% IRGB), PWM = 25.4%
03h C8h RED 2 IPLS = 3 (100% IRGB), PWM = 12.7%
04h 1Fh GREEN2 IPLS = 0 (25% IRGB), PWM = 50%
05h 10h BLUE2 IPLS = 0 (25% IRGB), PWM = 25.4%
06h 07h RED 3 IPLS = 0 (25% IRGB), PWM = 11.1%
07h 03h GREEN3 IPLS = 0 (25% IRGB), PWM = 4.8%
08h 01h BLUE3 IPLS = 0 (25% IRGB), PWM = 1.6%
09h 0h RED 4 IPLS = 0 (25% IRGB), PWM = 0%
0Ah 0h GREEN4 IPLS = 0 (25% IRGB), PWM = 0%
0Bh 0h BLUE4 IPLS = 0 (25% IRGB), PWM = 0%
0Fh 0Fh Boost Output Boost output voltage set to 4.7V
10h 07h Frequency Selections PWM frequency (FPWM[1:0] = 0, 9.92 kHz), Boost SW frequency = 2 MHz
11h CFh Enables NSTBY, EN_BOOST, EN_RGB4, EN_RGB3, EN_RGB2, EN_RGB1 = 1 (exit standby state, enable boost and rgb drivers)