The solution presented in Figure 3-3, Figure 3-4 and Figure 3-5 was based on modifications to the RTG4 development board. In a new RTG4 design, TI recommends a power distribution as the one shown in Figure 3-1. In this case, an isolated DC-DC converter using TI's portfolio of TPS7H500X-SP controllers is used to generate the 5-V input voltage to the switching and linear point of load regulators. The recommended power-up sequence for this power distribution is shown in Figure 3-2. Since the RTG4 supports DDR memories, a DDR termination regulator will be needed as part of the power distribution as shown in Figure 2-1. For such device, the TPS7H3301-SP has been included in this grounds-up recommended power distribution. The TPS7H3301-SP is TI's radiation hardened double data rate (DDR) 3-A termination regulator that supports all standard DDR memory configurations and incorporates a built-in reference voltage buffer, eliminating the need for an additional supply to produce the DDR reference. In addition, as it is a linear device, it provides significant area savings and simplicity when compared to switching devices that require inductor and more components for the device to operate. For more information, please refer to the TPS7H3301-SP product page. Notice the 1.5-V input voltage to the TPS7H3301-SP shown in Figure 3-1 is the high current supply providing the output current for the DDR termination voltage.

This implementation ensures all power-up sequencing requirements are met as well as providing board area savings as TI offers the smallest, thermally enhanced radiation hardened DC-DC converter and LDO packages in the industry (TPS7H1101A-SP: 11.00 mm × 9.60 mm, TPS50601-SP: 12.70 mm × 7.38 mm, TPS7H4001-SP: 21.59 mm × 7.62 mm).