DLPS052 October   2015 DLPA3000


  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Block Diagram
  4. Revision History
  5. Pin Configuration and Functions
    1.     Pin 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 Parameters
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Supply and Monitoring
        1. Supply
        2. Monitoring
          1. Block Faults
          2. Low Battery and UVLO
          3. Auto LED Turn Off Functionality
          4. Thermal Protection
      2. 7.3.2 Illumination
        1. Programmable Gain Block
        2. LDO Illum
        3. Illumination Driver A
        4. RGB Strobe Decoder
          1. Break Before Make (BBM)
          2. Openloop Voltage
          3. Transient Current Limit
        5. Illumination Monitoring
          1. Power Good
          2. Ratio Metric Overvoltage Protection
        6. Load Current and Supply Voltage
        7. Illumination Driver Plus Power FETS Efficiency
      3. 7.3.3 DMD Supplies
        1. LDO DMD
        2. DMD HV Regulator
          1. Power-Up and Power-Down Timing
        3. DMD/DLPC Buck Converters
        4. DMD Monitoring
          1. Power Good
          2. Overvoltage Fault
      4. 7.3.4 Buck Converters
        1. LDO Bucks
        2. General Purpose Buck Converters
        3. Buck Converter Monitoring
          1. Power Good
          2. Overvoltage Fault
        4. Buck Converter Efficiency
      5. 7.3.5 Auxiliary LDOs
      6. 7.3.6 Measurement System
      7. 7.3.7 Digital Control
        1. SPI
        2. Interrupt
        3. Fast-Shutdown in Case of Fault
        4. Protected Registers
        5. Writing to EEPROM
    4. 7.4 Device Functional Modes
    5. 7.5 Register Maps
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Typical Application Setup Using DLPA3000
        1. Design Requirements
        2. Detailed Design Procedure
        3. Application Curve
      2. 8.2.2 Typical Application with DLPA3000 Internal Block Diagram
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 SPI Connections
    4. 10.4 RLIM Routing
    5. 10.5 LED Connection
    6. 10.6 Thermal Considerations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Device Nomenclature
    2. 11.2 Related Links
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Package Option Addendum
      1. 12.1.1 Packaging Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)

Illumination Driver A

The illumination driver of the DLPA3000 is a buck converter with two internal low-ohmic N-channel FETs (see Figure 7). The theory of operation of a buck converter is explained in Understanding Buck Power Stages in Switchmode Power Supplies (SLVA057). For proper operation, selection of the external components is very important, especially the inductor LOUT and the output capacitor COUT. For best efficiency and ripple performance, an inductor and capacitor should be chosen with low equivalent series resistance (ESR).

DLPA3000 Illum_Buck.gifFigure 7. Typical Illumination Driver Configuration

Several factors determine the component selection of the buck converter, such as input voltage (SYSPWR), desired output voltage (VLED) and the allowed output current ripple. Configuration starts with selecting the inductor LOUT.

The value of the inductance of a buck power stage is selected such that the peak-to-peak ripple current flowing in the inductor stays within a certain range. Here, the target is set to have an inductor current ripple, kI_RIPPLE, less than 0.3 (30%). The minimum inductor value can be calculated given the input and output voltage, output current, switching frequency of the buck converter (ƒSWITCH= 600 kHz) and inductor ripple of 0.3 (30%):

Equation 1. DLPA3000 EQ_Illum_Buck_Lout.gif

Example: VIN= 12 V, VOUT= 4.3 V, IOUT= 6 A results in an inductor value of LOUT= 2.7 µH

Once the inductor is selected, the output capacitor COUT can be determined. The value is calculated using the fact that the frequency compensation of the illumination loop has been designed for an LC-tank resonance frequency of 15 kHz:

Equation 2. DLPA3000 EQ_Illum_Buck_fres.gif

Example: COUT= 41.7 µF given that LOUT= 2.7 µH. A practical value is 2 × 22 µF. Here a parallel connection of two capacitors is chosen to lower the ESR even further.

The selected inductor and capacitor determine the output voltage ripple. The resulting output voltage ripple VLED_RIPPLE is a function of the inductor ripple kI_RIPPLE, output current IOUT, switching frequency ƒSWITCH and the capacitor value COUT:

Equation 3. DLPA3000 EQ_Illum_Buck_VLED_RIPPLE.gif

Example: kI_RIPPLE= 0.3, IOUT= 6 A, ƒSWITCH= 600 kHz and COUT= 44 µF results in an output voltage ripple of VLED_RIPPLE= 8.5 mVpp

As can be seen, this is a relative small ripple.

It is strongly advised to keep the capacitance value low. The larger the capacitor value the more energy is stored. In case of a VLED going down, stored energy needs to be dissipated. This might result in a large discharge current. For a VLED step down from V1 to V2, while the LED current was I1. The theoretical peak reverse current is:

Equation 4. DLPA3000 EQ_I2max.gif

For the single-LED case, it is advised to keep COUT at maximum 44µF.

Two other components need to be selected in the buck converter. The value of the input-capacitor (pin ILLUM_A_VIN) should be equal to or greater than the selected output capacitance COUT, in this case >44 µF. The capacitor between ILLUM_A_SWITCH and ILLUM_A_BOOST is a charge pump capacitor to drive the high side FET. The recommended value is 100 nF.