NS LP3931 Manual

Dual rgb led driver with high current boost dc-dc converter

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LP3931

Dual RGB LED Driver with High Current Boost DC-DC

Converter

General Description

The LP3931 is a RGB LED driver with high current boost

DC-DC converter designed for portable wireless applica-

tions. It contains 2 sets of RGB LED drivers that are PWM-

driven with programmable color, intensity and blinking pat-

terns. They additionally feature a FLASH function to support

picture taking with camera-enabled cellular phones.

An efficient magnetic boost DC/DC converter provides the

required bias, operating from a single Li-Ion battery. The

DC/DC converter output voltage is user programmable for

adapting to different LED types and for efficiency optimiza-

tion.

All functions are software controllable through the SPI inter-

face and internal registers.

Typical Application

Features

n High Efficiency Programmable 300 mA Magnetic Boost

DC-DC converter

n 2 separately controlled PWM RGB LED drivers with

programmable color, brightness, turn on/off slopes and

blinking patterns

n FLASH function with up to 6 outputs, each up to

120 mA

n Functions software controlled through SPI interface

n Additional LED on/off and dimming hardware control

n Programmable low current Standby mode

n Low voltage digital interface down to 1.8V

n Space efficient 24-pin LLP package

Applications

n GSM Cellular Phones

n WCDMA, CDMA and CDMA2000 Phones

n PHS and PDC Cellular Phone

DS201173

August 2004

20117301

www.national.com

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Summary of Contents for NS LP3931

Page 1: General Description
General Description Features n High Efficiency Programmable 300 mA Magnetic Boost The LP3931 is a RGB LED driver with high current boost DC-DC converter DC-DC converter designed for portable wireless applica- tions. It contains 2 sets of RGB LED drivers that are PWM-...
Page 2: Ordering Information
Connection Diagrams and Package Mark Information 24-Lead LLP Package, 4 x 4 x 0.8 mm NS Package Number NSQAL024 20117303 20117302 Bottom View Top View 20117304 Package Mark — Top View Note: The actual physical placement of the package marking will vary from part to part. The package marking “XY” designates the date code.
Page 3: Pin Description
Pin Description Pin # Name Type Description Output Open Drain, Green LED2 Output Open Drain, Red LED2 GND_RGB Ground RGB Driver Ground Output Open Drain, Red LED1 Output Open Drain, Green LED1 Output Open Drain, Blue LED1 GND_BOOST Ground Power Switch Ground Output Open Drain, Boost Converter Power Switch Power...
Page 4: Absolute Maximum Ratings
= 25˚C. Limits in boldface type apply over the operating ambient temperature range (−40˚C ≤ T ≤ +85˚C). Unless otherwise noted, specifications apply to the LP3931 Typical Application Circuit (pg. 1) with: V = 2.775V, C = 0.1 µF, C = 10 µF, C...
Page 5: Block Diagram
Note 12: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) are used in setting electrical characteristics. Note 13: V pin (Bandgap reference output) is for internal use only. A capacitor should always be placed between V and GND1. Block Diagram 20117305 LP3931 Block Diagram www.national.com...
Page 6: Modes Of Operation
Modes of Operation RESET: In the RESET mode all the internal registers are reset to the default values (Boost output register 3Fh (5.0V), all other registers 00h). Reset is entered always if input NRST is LOW or internal Power On Reset is active.
Page 7: Spi Interface
SO is connected. The Address and LP3931 is compatible with the SPI serial bus specification Data are transmitted MSB first. The Slave Select signal SS and it operates as a slave. The transmission consists of must be low during the Cycle transmission.
Page 8 Magnetic Boost DC/DC Converter The LP3931 Boost DC/DC Converter generates a 4.1V–5.3V supply voltage for the LEDs from single Li-Ion battery (3V…4.5V). The output voltage is controlled with an 8-bit register in 9 steps. The converter is a magnetic switching PWM mode DC/DC converter with a current limit.
Page 9 Magnetic Boost DC/DC Converter (Continued) Boost Converter Topology 20117310 Magnetic Boost DC/DC Converter Electrical Characteristics Symbol Parameter Conditions Units 3.0V ≤ V ≤ 4.5V Load Current LOAD (FB) = 5V 1 mA ≤ I ≤ 300 mA Voltage Accuracy at FB Pin 3.0V ≤...
Page 10 Boost Output Voltage Control Boost Output Voltage Control User can control the boost output voltage by 8-bit boost output register as follows: Register 0DH BOOST Output Voltage Boost Output [7:0] (typical) 0000 0000 4.15 0000 0001 4.30 0000 0011 4.40 0000 0111 4.55 0000 1111...
Page 11 Boost Converter Typical Performance Characteristics = 3.6V, V = 5.0V if not otherwise stated. (Continued) 20117321 20117317 Boost Typical Waveforms at 100 mA Load Boost Startup with No Load 20117318 20117319 Boost Line Regulation Boost Load Regulation, 50 mA-100 mA www.national.com...
Page 12 Application Note AN1291 describes in detail the RGB driver 20117322 RGB PWM Operating Principle functionality of LP3933. The RGB driver in LP3931 is iden- tical with LP3933. RGB_START is the master enable control for the whole RGB function. The internal PWM and blinking control can be disabled by setting the RGB_PWM control LOW.
Page 13 RGB Driver Electrical Characteristics (R1, G1, B1, R2, G2, B2 outputs) Symbol Parameter Conditions Units Ω ON Resistance DS-ON Off State Leakage Current = 5V, LED driver off 0.03 µA LEAKAGE Maximum Sink Current (Note 5) Maximum Slope Period At Maximum Duty Setting 0.93 SMAX Minimum Slope Period...
Page 14 INDUCTOR, L output ripple magnitude. Multilayer ceramic capacitors with low ESR are the best choice. At the lighter loads, the low The LP3931’s high switching frequency enables the use of ESR ceramics offer a much lower V ripple than the the small surface mount inductor.
Page 15: Control Registers
Recommended External Components (Continued) List of External Components Symbol Symbol Explanation Value Unit Recommended Type Bypass Capacitor Ceramic, X7R VDD1 Bypass Capacitor Ceramic, X7R VDD2 Output Capacitor from FB to GND µF Ceramic, X7R/Y5V Input Capacitor from Battery Voltage to GND µF Ceramic, X7R/Y5V Bypass Capacitor...
Page 16: Application Examples
Application Examples 20117315 LP3931 with One RGB and One FLASH LED 20117316 LP3931 with Two RGB and One FLASH LED www.national.com...
Page 17: Physical Dimensions
Physical Dimensions inches (millimeters) unless otherwise noted 24-Lead LLP Package, 4 x 4 x 0.8 mm NS Package Number NSQAL024 LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION.