SNVS256E November   2003  – October 2024 LP3943

PRODUCTION DATA  

  1.   1
  2. 1Features
  3. 2Applications
  4. 3Description
  5. 4Pin Configuration and Functions
    1.     Pin Functions
  6. 5Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 I2C Interface (SCL and SDA Pins) Timing Requirements
    7. 5.7 Typical Characteristic
  7. 6Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
    4. 6.4 Device Functional Modes
    5. 6.5 Programming
      1. 6.5.1 I2C Data Validity
      2. 6.5.2 I2C START and STOP Conditions
      3. 6.5.3 Transferring Data
      4. 6.5.4 Auto Increment
    6. 6.6 Register Maps
      1. 6.6.1 Binary Format for Input Registers (Read-only)—Address 0x00 and 0x01
      2. 6.6.2 Binary Format for Frequency Prescaler and PWM Registers — Address 0x02 to 0x05
      3. 6.6.3 Binary Format for Selector Registers — Address 0x06 to 0x09
  8.   Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Reducing IQ When LEDs are OFF
      3. 7.2.3 Application Curve
    3. 7.3 System Examples
    4. 7.4 Power Supply Recommendations
    5. 7.5 Layout
      1. 7.5.1 Layout Guidelines
      2. 7.5.2 Layout Example
  9. 7Device and Documentation Support
    1. 7.1 Receiving Notification of Documentation Updates
    2. 7.2 Community Resources
    3. 7.3 Trademarks
  10. 8Revision History
  11.   Mechanical, Packaging, and Orderable Information

6.1 Overview

The LP3943 takes incoming data from the baseband controller and feeds them into several registers that control the frequency and the duty cycle of the LEDs. Two prescaler registers and two PWM registers provide two individual rates to dim or blink the LEDs (for more information on these registers, refer to Table 6-1). Each LED can be programmed in one of four states: ON, OFF, DIM0 rate, or DIM1 rate. Two read-only registers provide status on all 16 LEDs. The LP3943 can be used to drive RGB LEDs and/or single-color LEDs to create a colorful, entertaining, and informative setting. Alternatively, it can also drive RGB LED as a flashlight. This is particularly suitable for accessory functions in cellular phones and toys. Any LED pins not used to drive LED can be used for general purpose parallel input/output (GPIO) expansion.

The LP3943 is equipped with power-on reset that holds the chip in a reset state until VDD reaches VPOR during power up. Once VPOR is achieved, the LP3943 comes out of reset and initializes itself to the default state.

To bring the LP3943 into reset, hold the RST pin LOW for a period of TW. This puts the chip into its default state. The LP3943 can only be programmed after RST signal is HIGH again.