ADP3050 Analog Devices, ADP3050 Datasheet - Page 13

• Manufacturer Part Number: ADP3050
• Description: 200 kHz, 1 A Step-Down High-Voltage Switching Regulator
• Manufacturer: Analog Devices

Multilayer ceramic capacitors can be used in applications where
minimum output voltage ripple is a priority. They have a very
low ESR (a 22 μF ceramic can have an ESR one-fifth that of a
22 μF solid tantalum), but may require more board area for the
same value of output capacitance. A few manufacturers have
recently improved upon their low voltage ceramic capacitors,
providing a smaller package with a lower ESR (NEC Tokin,
Murata, Taiyo Yuden, and AVX). Several ceramics can be used
in parallel to give an extremely low ESR and a good value of
capacitance. If the design is cost sensitive and not severely space
limited, several aluminum electrolytic capacitors can be used in
parallel (their size and ESR are larger than ceramic and solid
tantalum). OS-CON capacitors can also be used, but they are
typically larger and more expensive than ceramic or solid
tantalum capacitors.
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Choosing an Output Capacitor
Use the following steps to choose an appropriate capacitor.
1.
2.
3.
4.
Decide the maximum output ripple voltage for the design,
and this determines your maximum ESR (remember that
V
between 0.5% and 2% of the output voltage. To lower the
output voltage ripple, there are only two choices: either
increase the inductor value, or use an output capacitor with
a lower ESR.
Decide what type of capacitor to use (tantalum, ceramic, or
others). Many more values, sizes, and voltage ratings are
available, so contact each manufacturer for a complete
product list. If a certain type of capacitor must be used and
space permits, use several devices in parallel to reduce the
total ESR.
Check the capacitor voltage rating and ripple current rating
to ensure it works for the application in question. These
ratings are derated for higher temperatures, so always check
the manufacturer’s data sheet.
Make sure the final choice for the output capacitor has
been optimized for cost, size, availability, and performance
yet still meets the required capacitance. The recommended
capacitance is in the 47 μF to 220 μF range.
RIPPLE
≈ ESR × I
RIPPLE
). Typical output ripple voltages range
ADP3050