DLPS202A October 2020 – August 2024 TPS99000S-Q1
PRODUCTION DATA
The power supply architecture depends on the amount of power required for the illumination source. For HUD applications that require precise color and white point control, it is highly recommended to preregulate the illumination power supply, as voltage variations can cause variations in the LED output. For non-color critical applications, the designer may choose to completely isolate the illumination driver. In addition, if two or more LEDs are driven in series, then the preregulated voltage must be higher than the voltage of the LEDs. The different architectures are shown below.
Note that the architectures make use of the LM25118 as a preregulator. This part uses a buck-boost architecture that enables it to supply the required 6.5V with a battery voltage input of 6V to 18V. If the battery input can be assured to be above the 6.5V output voltage, then a buck architecture can be used instead, resulting in BOM savings.
In this application, the same preregulator is used to power the 6.5V rail as well as the LM3409. Since the LM3409 input voltage must be kept above 6V, the preregulator is set to 6.5V.
In this application, the preregulator must be designed to operate at a higher output voltage to drive two LEDs in series. Because the TPS99000S-Q1 requires a VIN from 5.5V to 7V, a small buck regulator is used to generate a 6V power rail.
In this application, the power used to drive the illumination is separate from the TPS99000S-Q1. This is possible in applications where the illumination driver can be very simple. Although the LM25118 is shown here, a different regulator would likely be selected in this application because the maximum current requirements are much less with the illumination power path removed.