8.2.1 Design Requirements

A pico-projector is created by using a DLP chip set comprised of DLP2010 (.2 WVGA) DMD, DLPC3430 or DLPC3435 controller and DLPA2005 PMIC/LED driver. The DLPC3430 or DLPC3435 does the digital image processing, the DLPA2005 provides the needed analog functions for the projector, and DMD is the display device for producing the projected image. In addition to the three DLP chips in the chip set, other chips may be needed. At a minimum a flash part is needed to store the software and firmware to control the DLPC3430 or DLPC3435. The illumination light that is applied to the DMD is typically from red, green, and blue LEDs. These are often contained in three separate packages, but sometimes more than one color of LED die may be in the same package to reduce the overall size of the pico-projector. For connecting the DLPC3430 or DLPC3435 to the front end for receiving images parallel interface is used. While using parallel interface, I²C should be connected to the front end for sending commands to the DLPC3430 or DLPC3435. The only power supplies needed external to the projector are the battery (SYSPWR) and a regulated 1.8 V supply. The entire pico-projector can be turned on and off by using a single signal called PROJ_ON. When PROJ_ON is high, the projector turns on and begins displaying images. When PROJ_ON is set low, the projector turns off and draws just microamps of current on SYSPWR. When PROJ_ON is set low, the 1.8 V supply can continue to be left at 1.8 V and used by other non-projector sections of the product. If PROJ_ON is low, the DLPA2005 will not draw current on the 1.8 V supply.

8.2.2 Detailed Design Procedure

For connecting together the DLP2010, DLPC3430 or DLPC3435 and DLPA2005, see the reference design schematic. When a circuit board layout is created from this schematic a very small circuit board is possible. An example small board layout is included in the reference design data base. Layout guidelines should be followed to achieve a reliable projector. The optical engine that has the LED packages and the DMD mounted to it is typically supplied by an optical OEM who specializes in designing optics for DLP projectors.

8.2.3 Application Curves

As the LED currents that are driven time-sequentially through the red, green, and blue LEDs are increased, the brightness of the projector increases. This increase is somewhat non-linear, and the curve for typical white screen lumens changes with LED currents. It’s assumed that the same current amplitude is applied to the red, green, and blue LEDs.

8.3.1 Design Requirements

All applications using the DLP 0.2-inch WVGA chipset require the:

• DLPC150 controller, and
• DLPA2005 PMIC, and
• DLP2010 or DLP2010NIR DMD

components for operation. The system also requires an external parallel flash memory device loaded with the DLPC150 configuration and support firmware. DLPC150 does the digital image processing and formats the data for the DMD. DLPA2005 PMIC provides the needed analog functions for the DLPC150 and DLP2010 or DLP2010NIR. The chipset has several system interfaces and requires some support circuitry. The following interfaces and support circuitry are required:

• DLPC150 system interfaces:
  • Control interface
  • Trigger interface
  • Input data interface
  • Illumination interface
• DLPC150 support circuitry and interfaces:
  • Reference clock
  • PLL
  • Program memory flash interface
• DMD interfaces:
  • DLPC150 to DMD digital data
  • DLPC150 to DMD control interface
  • DLPC150 to DMD micromirror reset control interface

8.3.2 Detailed Design Procedure

8.3.3 Application Curve

In a reflective spectroscopy application, a broadband light source illuminates a sample and the reflected light spectrum is dispersed onto the DLP2010NIR. A microprocessor in conjunction with the DLPC150 controls individual DLP2010NIR micromirrors to reflect specific wavelengths of light to a single point detector. The microprocessor uses an analog-to-digital converter to sample the signal received by the detector into a digital value. By sequentially selecting different wavelengths of light and capturing the values at the detector, the microprocessor can then plot a spectral response to the light. This systems allows the measurement of the collected light and derive the wavelengths absorbed by the sample. This process leads to the absorption spectrum shown in Figure 18.