Low voltage power supply unit

In this post, we introduce simple and flexible, regulated low voltage power supply unit. This power supply has provision for 4 outputs such as 1.5V, 1.8V, 2.5V and 3.3V. We mainly build this low voltage power supply unit to test (and power-up) low voltage MCUs, CPLDs, and radio receivers. For this power supply, we choose 1.8V, 2.5V and 3.3V to get it compatible with most of the LVTTL/LVCMOS devices. Other than that, we include 1.5V because there are several analog ICs are available for that voltage level.

This power supply unit is based on LM1117/AMS1117 voltage regulator series and for this design, we use AMS1117-1.5, AMS111-1.8, AMS1117-2.5, and AMS1117-3.3 fixed voltage regulators. Except to above regulators, this board can be used with AMS1117-2.85 and AMS1117-5.0 regulators.

Internal view of the low voltage power supply unit.

In our prototype, we use center-tapped 6V (1A) step down transformer with this power supply unit. All the wiring diagrams to transformer and rotary switch are provided with the schematic.

The given PCB design for this power supply unit is based on the SOT-223 (SMD) version of voltage regulators. Even though it uses SMD components this PCB can build with single side PCB. The dimension of the PCB is set to 89mm × 69mm. All PCB designs and schematics of this power supply unit are available to download at google drive.

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