How to select input capacitors?

The first objective in selecting input capacitors is to reduce the ripple voltage amplitude seen at the input of the module. Ceramic capacitors placed right at the input of the regulator are effective in achieving this.

What is a variable capacitor?

Variable capacitors are made as trimmers, that are typically adjusted only during circuit calibration, and as a device tunable during operation of the electronic instrument. The most common group is the fixed capacitors. Many are named based on the type of dielectric.

What type of capacitor should I use?

It is recommended to use a combination of Aluminum Electrolytic (AlEl) and ceramic capacitors. Ceramic capacitors have low ESR and they can reduce the input voltage peak-to-peak ripple, which, in turn, reduces the input ripple current for the input bulk capacitors to handle. Figure 3. Input Capacitor RMS Current Calculation Table 3.

What are the two types of capacitors?

Capacitors are divided into two mechanical groups: Fixed-capacitance devices with a constant capacitance and variable capacitors. Variable capacitors are made as trimmers, that are typically adjusted only during circuit calibration, and as a device tunable during operation of the electronic instrument. The most common group is the fixed capacitors.

How do variable capacitors change capacitance?

Altering the physical parameters that dictate capacitance, such as the conductor plates' surface area (A), spacing between them (d), and permittivity (ε) of the dielectric material between them, can produce this shift in capacitance. The adjustment of the distance (d) between the plates is another feature of certain variable capacitors.

How do I choose the best polymer capacitors?

Find the optimal products for you based on the product type, voltage class, temperature and ripple current. TDK Corporation (TSE:6762) presents the B40910 series of hybrid polymer capacitors which can handle up to 4.6 A (100 kHz, +125 °C).