7.3.2 RGB Strobe Decoder

DLPA2000 contains RGB color-sequential circuitry that is composed of three NMOS switches, the LED driver, the strobe decoder, and the LED current control. The NMOS switches are connected to the terminals of the external LED package and turn the currents through the LEDs on and off. Package connections are shown in Figure 6 and Figure 9 and the corresponding switch map is in Table 1.

The LED_SEL[1:0] signals typically receive a rotating code switching from RED to GREEN to BLUE and then back to RED. When the LED_SEL[1:0] input signals select a specific color, the NMOSFETs are controlled based on the color selected, and a 10-bit current control DAC for this color is selected that provides a control current to the RGB LEDs' feedback control network.

Figure 6. Switch Connection for a Common-Anode LED Assembly

The switching of the three NMOS switches is controlled such that switches are returned to the open position first before the closed connections are made (break before make). The dead time between opening and closing switches is controlled through the BBM register. Switches that already are in the closed position (and are to remain in the closed state according to the SWCNTRL register) are not opened during the BBM delay time.

Figure 7. BBM Timing (See Register 0Bh in Figure 26)