Collection! 19 methods and techniques for converting 5V to 3.3V

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Collection! 19 methods and techniques for converting 5V to 3.3V [Copy link]

Tip 1: Use an LDO regulator to power a 3.3V system from a 5V supply

Standard three-terminal linear regulators typically have a dropout voltage of 2.0-3.0V. They cannot be used to reliably convert 5V to 3.3V. Low Dropout (LDO) regulators, which have a dropout voltage of several hundred millivolts, are ideal for such applications. Figure 1-1 is a block diagram of a basic LDO system with the corresponding currents labeled. As can be seen from the figure, an LDO consists of four main parts:

1. Turn on the transistor

2. Bandgap reference source

3. Operational Amplifier

4. Feedback resistor divider

When choosing an LDO, it is important to know how to differentiate between the various LDOs. The device's quiescent current, package size, and model are important device parameters. Determining the various parameters based on the specific application will result in the optimal design.

The quiescent current IQ of an LDO is the ground current IGND of the device when the device is operating at no load. IGND is the current used by the LDO for voltage regulation. When IOUT>>IQ, the efficiency of the LDO can be approximated by dividing the output voltage by the input voltage. However, at light loads, IQ must be included in the efficiency calculation. LDOs with lower IQ have higher light load efficiency. Improvements in light load efficiency have a negative impact on LDO performance. LDOs with higher quiescent current respond faster to sudden changes in line and load.

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Tip 2: Low-cost power supply system using Zener diodes

A low-cost voltage regulator solution using a Zener diode is detailed here.

A simple, low-cost 3.3V regulator can be made using a Zener diode and a resistor, as shown in Figure 2-1. This circuit is a cost-effective alternative to an LDO regulator in many applications. However, this regulator is more load sensitive than an LDO regulator. It is also less energy efficient because R1 and D1 always dissipate power. R1 limits the current flowing into D1 and the PICmicro MCU, keeping VDD within the allowable range. The value of R1 needs to be carefully considered because the reverse voltage of the Zener diode will change as the current through the Zener diode changes.

R1 is chosen so that at maximum load - usually when the PICmicro MCU is running and driving its output high - the voltage drop across R1 is low enough to keep the PICmicro MCU operating while at minimum load - usually when the PICmicro MCU is reset - VDD does not exceed the power rating of the Zener diode nor the maximum VDD of the PICmicro MCU.