DLPU066A March   2018  – April 2022 DLP3030-Q1

 

  1. 1Calibration Purpose
    1. 1.1 Calibration Purpose
    2. 1.2 Goal of Calibration
  2. 2Calibration Software and Tools
    1. 2.1 Calibration Software and Tools
  3. 3Calibration Setup
    1. 3.1 Calibration Setup
  4. 4Calibration Overview and Theory
    1. 4.1 Goal of Calibration
    2. 4.2 Calibration Background
      1. 4.2.1 Calibration File Parameters
      2. 4.2.2 Coarse Adjustment Parameter Combinations
    3. 4.3 Calibration Process
      1. 4.3.1 Calibration Pre-work: Coarse Combination Determination
      2. 4.3.2 Temperature Charaterization
      3. 4.3.3 Production PGU Calibration
  5. 5Calibration Pre-work
    1. 5.1 Pre-work Overview
    2. 5.2 Coarse Combination Determination
    3. 5.3 Strategically Adjusting Coarse Combination Parameters
      1. 5.3.1 LDC Index
      2. 5.3.2 Optical Sensor Feedback Gain
      3. 5.3.3 Current Limit
    4. 5.4 Coarse Combination Strategies
  6. 6Calibration Procedure
    1. 6.1 Calibration Procedure Overview
    2. 6.2 Calibration Sweep Setup and Coarse Combinations
    3. 6.3 Temperature Characterization
    4. 6.4 Production PGU Calibration
    5. 6.5 Generating a Calibration File
  7. 7Revision History

4.2.1 Calibration File Parameters

For each input backlight value, a series of system parameters are set by the Piccolo microcontroller.Table 4-1 lists all of the parameters defined in the calibration file. The parameters can be divided into two categories: coarse adjustment and fine adjustment parameters.

Coarse adjustment parameters change the brightness of the system significantly. Therefore, a combination of these parameters is assigned to a range of backlight values.

Fine adjustment parameters provide very fine control of the system's brightness and color point. Therefore, once a combination of coarse adjustment parameters is assigned to a backlight range, the fine adjustment parameters can be modified to achieve the desired color point and brightness. Each backlight value has a unique set of fine adjustment parameters, but not all of these are stored in the calibration file. Interpolation is used to reduce the number of values that need to be stored.

Table 4-1 Calibration Parameters
Parameter Type Parameter Description
Coarse Adjustment LDC Index Total time the LEDs are on, calculated according to the following variables:  
Continuous Mode: LED sequence multiplied by time attenuation percentage.  
Discontinuous Mode: LED duty cycle and the number of pulses in each bit of the sequence.  
For more explanation, see the LED Driver for DLP3030-Q1 Displays Application Note (DLPA084).
LED Driver Current Limit PWM The maximum current allowed through the LEDs or the shunt FET.
Optical Feedback Amplifier Gain Amount of gain applied to the response of the photodiode used to sense LED light. Higher gain results in lower brightness. With a higher gain, less LED light is required to achieve the target.
Fine Adjustment R/G/B PWM The target optical response requested from each LED.

The final calibration file is a series of look up tables. Each table is associated with a specific temperature. Within each table there are rows that map backlight values to the coarse and fine adjustment parameters described in Table 4-1. A few example calibration rows are shown in Table 4-2 below. During calibration pre-work, the coarse parameter columns (LDC, Gain, Current Limit) are inputs from the user while the fine adjustment parameters (R/G/B PWM columns) are generated by the calibration algorithm of the ACP.

Table 4-2 Example Calibration Row
Calibration RowBacklight LevelLDCGainCurrent LimitRed PWMGreen PWMBlue PWM
16553501x59000268725672835698
23513201x59000134752305621443
33513121x59000254365433434756
42245621x5900090041328712449