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

3 Description

The LP3943 is an integrated device capable of independently driving 16 LEDs. This device also contains an internal precision oscillator that provides all the necessary timing required for driving each LED. Two prescaler registers, along with two PWM registers, provide a versatile duty-cycle control. The LP3943 contains the ability to dim LEDs in SMBUS/I2C applications where it is required, to cut down on bus traffic.

Traditionally, dimming LEDs using a serial shift register such as 74LS594/5 requires a large amount of traffic on the serial bus. The LP3943 instead requires only the setup of the frequency and duty cycle for each output pin; from then on, only a single command from the host is required to turn each individual open drain output to an ON or OFF state, or to cycle a programmed frequency and duty cycle. Maximum output sink current is 25mA per pin and 200mA per package. Any ports not used for controlling the LEDs can be used for general purpose input/output expansion.

Device Information(1)
PART NUMBERPACKAGEBODY SIZE (NOM)
LP3943WQFN (24)4.00mm × 4.00mm
(1) For all available packages, see the orderable addendum at the end of the data sheet.
LP3943 Typical Application Circuit Typical Application Circuit