Vermes
Advanced Member level 4
The main element of presented device is system A8498. The converter is definitely a better alternative than the popular stabilizer 7805 or LDO e.g. > LM1117-3.3.
The converter can be used everywhere to power any system with a microcontroller or digital without any concern about possible interferences. It is very good for systems using ADC.
Very high efficiency of the converter is provided by the fact, that the device does not heat up as the radiator, as it happens in the case of linear stabilizers or LDO. A wide range of input voltages is another advantage. In this case, the upper limit is restricted to 24V, because a capacitor to 25V was applied at the input, but there is a possibility to increase the voltage to 35V to gain a broader range.
Two different output voltages +3,3V or +5V can be reached at the output using a jumper.
The output current with a choke used is 1A and practically cool system until the current consumption of 600-700mA. After that, it gets slightly warm to 1A.
Size of the converter is 2-3mm bigger than dimensions of the chip 7805.
Simple control is implemented by two transistors NPN (SMD in housings SOT323). They provide two pins, which, after a momentary short circuit, allow the converter to start, unless the output voltage is given to the second input (OFF). OFF input can be connected to any microcontroller pin, which has the ability to programmatically turn off the power.
Below there are three modes of operation of the converter:
It operates really satisfactorily and works very nice in practice. Power supply can be turned on using only one microswitch. The processor can continue to have high state on pin OFF of the converter and the system works.
Some photos of the converter made (despite the headers) in SMD. Resistors used are from 0405 to 0603.
Link to original thread (useful attachment) – Przetwornica IN 8-24V / OUT +3.3V/+5V zamiast 7805 + sterowanie