DLPS132 May   2018 DLPA4000

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      System Block Diagram
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Description
    3. 7.3 Feature Description
      1. 7.3.1 Supply and Monitoring
        1. 7.3.1.1 Supply
        2. 7.3.1.2 Monitoring
          1. 7.3.1.2.1 Block Faults
          2. 7.3.1.2.2 Low Battery and UVLO
          3. 7.3.1.2.3 Thermal Protection
      2. 7.3.2 Illumination
        1. 7.3.2.1 Programmable Gain Block
        2. 7.3.2.2 LDO Illumination
        3. 7.3.2.3 Illumination Driver A
        4. 7.3.2.4 External MOSFETs
          1. 7.3.2.4.1 Gate series resistor (RG)
          2. 7.3.2.4.2 Gate series diode (DG)
          3. 7.3.2.4.3 Gate parallel capacitance (CG)
        5. 7.3.2.5 RGB Strobe Decoder
          1. 7.3.2.5.1 Break Before Make (BBM)
          2. 7.3.2.5.2 Openloop Voltage
          3. 7.3.2.5.3 Transient Current Limit
        6. 7.3.2.6 Illumination Monitoring
          1. 7.3.2.6.1 Power Good
          2. 7.3.2.6.2 RatioMetric Overvoltage Protection
      3. 7.3.3 External Power MOSFET Selection
        1. 7.3.3.1 Threshold Voltage
        2. 7.3.3.2 Gate Charge and Gate Timing
        3. 7.3.3.3 On-resistance RDS(on)
      4. 7.3.4 DMD Supplies
        1. 7.3.4.1 LDO DMD
        2. 7.3.4.2 DMD HV Regulator
        3. 7.3.4.3 DMD/DLPC Buck Converters
        4. 7.3.4.4 DMD Monitoring
          1. 7.3.4.4.1 Power Good
          2. 7.3.4.4.2 Overvoltage Fault
      5. 7.3.5 Buck Converters
        1. 7.3.5.1 LDO Bucks
        2. 7.3.5.2 General Purpose Buck Converters
        3. 7.3.5.3 Buck Converter Monitoring
          1. 7.3.5.3.1 Power Good
          2. 7.3.5.3.2 Overvoltage Fault
      6. 7.3.6 Auxiliary LDOs
      7. 7.3.7 Measurement System
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1 SPI
      2. 7.5.2 Interrupt
      3. 7.5.3 Fast-Shutdown in Case of Fault
      4. 7.5.4 Protected Registers
      5. 7.5.5 Writing to EEPROM
    6. 7.6 Register Maps
  8. 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 Component Selection for General-Purpose Buck Converters
    3. 8.3 System Example With DLPA4000 Internal Block Diagram
  9. 9 Power Supply Recommendations
    1. 9.1 Power-Up and Power-Down Timing
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 LED Driver
        1. 10.1.1.1 PowerBlock Gate Control Isolation
        2. 10.1.1.2 VIN to PowerBlocks
        3. 10.1.1.3 Return Current from LEDs and RSense
        4. 10.1.1.4 RC Snubber
        5. 10.1.1.5 Capacitor Choice
      2. 10.1.2 General Purpose Buck 2
      3. 10.1.3 SPI Connections
      4. 10.1.4 RLIM Routing
      5. 10.1.5 LED Connection
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Device Nomenclature
    2. 11.2 Receiving Notification of Documentation Updates
    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)
Orderable Information

7.3.3.3 On-resistance RDS(on)

Consider two issues relative to the drain-to-source on-resistance (RDS(on)) to select a MOSFET. The first consideration is for the high-side MOSFET of the illumination buck-converter the RDS(ON) is a factor in the over-current detection. Secondly, for the other four MOSFETs the power dissipation drives the choice of the MOSFETs RDS(on).

The DLPA4000 measures the drain-to-source voltage drop of the high-side MOSFET when energized to detect an overcurrent situation. When the device detection circuit triggers, and de-energizes the high-side FET, the high-side drive over current threshold (VDC-Th ) is 185 mV . Use Equation 8 to calculate the actual current level, (IOC) that trigger the overcurrent detection.

Equation 8. DLPA4000 q_ioc1_dlps132.gif

Use the on-resistance specification listed in the MOSFET datasheet for a high-temperature condition.For example, the CSD87350Q5D NexFET specifies the on-resistance of 5 mΩ at 125 °C. The overcurrent level for a design that uses this MOSFET is 37 A. This MOSFET is a good choice for a 32-A application.

Power dissipation due to conduction losses determines the on-resistance selection for the low-side MOSFET and the three LED selection MOSFETs. Use Equation 9 to calculate the power dissipated in these MOSFETs.

Equation 9. DLPA4000 q_pdiss_dlps132.gif

where

  • IDS is the FET current

The lower the on-resistance the lower the power dissipation. For example, the on-resistance specified for the CSD17556Q5B MOSFET is 1.2 mΩ. For a drain-to-source current of 32 A with a duty cycle of 25% (when the MOSFET is used as LED selection switch) the dissipation is approximately 0.3 W.