8.2.1 Application Overview

Figure 21 shows the system block diagram for a DLP headlight module. The system uses the DLPC230-Q1, TPS99000-Q1, and the DLP5531-Q1 automotive DMD to enable a headlight projection system with unprecedented resolution and grayscale light control. The combination of the DLPC230-Q1 and TPS99000-Q1 removes the need for external SDRAM and a dedicated microprocessor. The chipset manages the illumination control of LED sources, power sequencing functions, and system management functions. Additionally, the chipset supports numerous system diagnostic and built-in self test (BIST) features. The following paragraphs describe the functionality of the chipset used for a headlight projection system in more detail.

The DLPC230-Q1 is a controller for the DMD and the light sources in the DLP headlight module. It receives input video from the host and synchronizes DMD and light source timing in order to achieve the desired video. The DLPC230-Q1 formats input video data that is displayed on the DMD. It synchronizes these video segments with light source timing in order to create a video with grayscale shading.

The DLPC230-Q1 receives inputs from a host processor in the vehicle. The host provides commands and input video data. Host commands can be sent using either the I²C bus or SPI bus. The bus that is not being used for host commands can be used as a read-only bus for diagnostic purposes. Input video can be sent over an OpenLDI bus or a parallel 24-bit bus. The 24-bit bus can be limited to only 8-bits of data for single light source systems such as headlights. The SPI flash memory provides the embedded software for the DLPC230-Q1’s ARM core, any calibration data, and default settings. The TPS99000-Q1 provides diagnostic and monitoring information to the DLPC230-Q1 using an SPI bus and several other control signals such as PARKZ, INTZ, and RESETZ to manage power-up and power-down sequencing. The TMP411 uses an I²C interface to provide the DMD array temperature to the DLPC230-Q1.

The outputs of the DLPC230-Q1 are configuration and monitoring commands to the TPS99000-Q1, timing controls to the LED or laser driver, control and data signals to the DMD, and monitoring and diagnostics information to the host processor. The DLPC230-Q1 communicates with the TPS99000-Q1 over an SPI bus. It uses this to configure the TPS99000-Q1 and to read monitoring and diagnostics information from the TPS99000-Q1. The DLPC230-Q1 sends drive enable signals to the LED or laser driver, and synchronizes this with the DMD mirror timing. The control signals to the DMD are sent using a sub-LVDS interface.

The TPS99000-Q1 is a highly integrated mixed-signal IC that controls DMD power, the timing and amplitude of the LEDs or lasers, and provides monitoring and diagnostics information for the DLP headlight module. The power sequencing and monitoring blocks of the TPS99000-Q1 properly power up the DMD and provide accurate DMD voltage rails (–16 V, 8.5 V, and 10 V), and then monitor the system’s power rails during operation. The integration of these functions into one IC significantly reduces design time and complexity. The TPS99000-Q1 also has several output signals that can be used to control a variety of LED or laser driver topologies. The TPS99000-Q1 has several general-purpose ADCs that designers can use for system level monitoring, such as over-brightness detection.

The TPS99000-Q1 receives inputs from the DLPC230-Q1, the power rails it monitors, the host processor, and potentially several other ADC ports. The DLPC230-Q1 sends configuration and control commands to the TPS99000-Q1 over an SPI bus and several other control signals. The DLPC230-Q1’s clocks are also monitored by the watchdogs in the TPS99000-Q1 to detect any errors. The power rails are monitored by the TPS99000-Q1 in order to detect power failures or glitches and request a proper power down of the DMD in case of an error. The host processor can read diagnostics information from the TPS99000-Q1 using a dedicated SPI bus, which enables independent monitoring. Additionally the host can request the image to be turned on or off using a PROJ_ON signal. Lastly, the TPS99000-Q1 has several general-purpose ADCs that can be used to implement system level monitoring functions.

The outputs of the TPS99000-Q1 are diagnostic information and error alerts to the DLPC230-Q1, and control signals to the LED or laser driver. The TPS99000-Q1 can output diagnostic information to the host and the DLPC230-Q1 over two SPI buses. In case of critical system errors, such as power loss, it outputs signals to the DLPC230-Q1 that trigger power down or reset sequences. It also has output signals that can be used to implement various LED or laser driver topologies.

The DMD is a micro-electro-mechanical system (MEMS) device that receives electrical signals as an input (video data), and produces a mechanical output (mirror position). The electrical interface to the DMD is a sub-LVDS interface with the DLPC230-Q1. The mechanical output is the state of more than 1.3 million mirrors in the DMD array that can be tilted ±12°. In a projection system the mirrors are used as pixels in order to display an image.