Power Supply Schematic

[Billi Mayhue]

Beloware my three different needs of powersupply for low noise applications(Analog Front end using THS4541 and ADC3669) for which i have chosen TPS54120, I request TI to kindly drop comments if any major flaws are observed in the design.

I am wondering if you have looked at the TPS62912 or TPS62913 for this application. The noise and ripple performance of the device may meet your needs and has been used on several AFE and ADC designs shown on the product page at www.ti.com\tps62913. The efficiency would also be better, as well as the solution size.

For the output RMS noise, TPS54120 is better since there is a LDO inside. If you can accept the higher RMS noise level, you may consider TPS62913/912 since they have much better efficiency and solution size.

It is true that 4uVrms is lower than 20uVrms as a noise figure. The real question is what do you need in your application. It may be that you do not need 4uVrms, but can accept the noise of the TPS62913.

Yes, LDO_GND and PGND should be different for all three regulators. The LDO_GND and PGND should be connected together locally at each regulator side. Each regulator should refer to EVM user's guide layout.

The final project I wanted to build was a wall adapter with a USB socket to charge my iPhone. But first I wanted to start by creating a simple circuit that converts from the main power voltage, 220V or 110V, to 5V.

Caution: Do NOT connect anything you make yourself to the power mains if you are not 100% sure about what you are doing. Doing it wrong can cause serious damage, even death. Use the information provided here at your own risk.

If you want a perfectly safe and extremely useful power supply circuit, you should check out this portable USB charger that I built. It even includes a downloadable step-by-step tutorial on how to build it yourself.

There are a lot of opinions on the web about these capacitors. Some suggest 0.1 F capacitors, and others suggest 100 F capacitors. And some suggest using both a 0.1 F and a 100 F capacitor in parallel.

I bought this Chinese HW-131 breadboard power supply, which seems to be a Chinese clone of another Chinese product, the YwRobot MB U2. There are reports of unreliability with that device run off 12V, the suggestion is to run it of less than 12V if you are drawing notable power from it because heatsinking is marginal, using the small board. And definitely test all the output voltages before wiring this to something valuable.

It uses a AMS1117 3.3 and 5V regulator, and the minimum input voltage is 6.5V, due to the regulator dropout of 1.3V, so I will look around for something more suited to this. A breadboard tends to get shorts easily, and I could see the AMS1117 getting shirty trying to dissipate 12W into a short at 1A current limit ? The schematic matches this Addicore one

Absolute maximum junction temp is stated at 125C, and their example calculations say a good board will get thermal resistance of 45C/W, so if we start at 20C the chip can dissipate 2W max. I favour 12V since I can split the 12V off an existing LED lamp power supply, and sockets are a premium around the computer.

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