I am doing a project where the components require 3.3v input instead of 5v, but my arduino pro mini can only supply 5v. Thus, I bought a lm1117t-3.3 voltage regulator to regulate the voltage, but the output from the voltage regulator is not 3.3v, but around 1v. This is the way I connected the voltage regulator, please give me some suggestions to overcome this problem, thank you.
Electrical – How to use a LM1117T-3.3 voltage regulator to convert voltage
voltage-regulator
Related Solutions
The datasheet states that 2.2 uF is a minimum required for for stability. The typical output capacitance (Table 3) is stated as 10 uF. Adding more capacitance will smooth the output more and ensure better stability, but there are some side effects (below).
Just to make all of this clear as to why you need this capacitance, see the figure below. An LDO is simply a transistor (A) that is controlled by a feedback loop (B and C). The error amplifier is trying to make B equal to the internally generated Reference Voltage.
Now when a large load current is pulsed (like in a digital circuit), Vout will droop. This makes B too low, then C has to drive A on harder so it can compensate. This takes time. So if the pulses of load current are too fast, the loop will not be able to compensate quickly enough, and you can have oscillation.
The solution is to put a charge bank, i.e. a capacitor out there to source the quick pulses of current, and the slower job of controlling the average current is left to the regulator.
So why not go insanely big on this capacitance? There are a couple of reasons:
- Cost. Big caps cost more.
- Space. They take up more space.
- Charge/discharge time. When you turn the circuit on, the capacitor has to charge up. This will cause the voltage on Vout to more slowly rise. Some circuits don't like to turn on slowly. Also, the charge has to be discharged when powering down. This is usually less important.
Finally, the input capacitance question. This is usually less clearly defined. The main point that is important is that you have a good enough source so that the LDO internal reference works well. A good idea is to look at what the datasheet test circuits use. This one shows a 0.1 uF capacitor placed on the input.
It cannot be either the PAM2301/AME5110, this is because those are switching regulators and there are no inductors on that board's top. Secondly the fact that there SMD codes are BA*** or BAR** respectively which does not match your model.
It is possible that it is RT9193 5 volt LDO regulator from richtek. This is as its code is BA, the LG is the lot code. And it is obvious it is the 5v version because of your VCC reading.
The manual is here, this is found on s-manuals where there is a table of smd codes linking to datasheets where you can look for the respective component, this works as you can look for the respective component according to functionality.
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Best Answer
This is how a typical LM1117 3 Pin Fixed Regulator is shown in circuit schematics:
This is symbolic/logical, NOT! Physically.
This is how they are typically physically wired, text side forward:
If you physically wired it as you show, Vin-Gnd-Vout, that will not work, and may have damaged it.
Of course, not all regulators use this pin out. The LM780x series does use Vin-Gnd-Vout. Always check the data sheet for your part's manufacturer.
Additionally, the LM1117 series requires a 10 µF Tantalum output capacitor. It may also need an input capacitor depending on how far the power supply is. It also has a minimum output load to be stable. 5 mA or so should be enough. A Led + Resistor would work.