Application Notes

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ATH06T033 & ATH06T05 Series

Table 2-1: Recommended Input/Output Capacitors

ATH06T033/T05: Capacitor Recommendations

Input Capacitor

The recommended input capacitance is determined by

100 µF minimum capacitance, and 300 mA (rms) mini-

mum ripple current rating.

Ripple current and less than 300 m

Ω equivalent series

resistance (ESR) values are the major considerations,

along with temperature, when designing with different

types of capacitors.

Tantalum capacitors have a recommended minimum volt-

age rating of twice 2

× (the maximum DC voltage + AC

ripple). This is standard practice for tantalum capacitors

to insure reliability.

Output Capacitors (Optional)

The ESR of the recommended capacitors is equal to or

less than 300 m

Ω. Electrolytic capacitors have marginal

ripple performance at frequencies greater than 400 kHz

but excellent low frequency transient response. Above the

ripple frequency, ceramic capacitors are necessary to

improve the transient response and reduce any high

frequency noise components apparent during higher

current excursions.

Tantalum/ Ceramic Capacitors

Tantalum capacitors are acceptable on the output bus.

Tantalum, Os-con, or ceramic capacitor types are recom-

mended for applications where ambient temperatures fall

below 0 °C. Ceramic capacitors may be used instead of

electrolytic types on both the input and output bus. The

input bus must have the minimum amount of capacitance.

A single 10 µF ceramic capacitor may also be used on the

output bus to reduce output ripple.

Capacitor Table

Table 2-1 identifies the characteristics of capacitors from

a number of vendors with acceptable ESR and ripple

current (rms) ratings. The number of capacitors required

at both the input and output buses is identified for

each capacitor type.

This is not an extensive capacitor list. Capacitors from other

vendors are available with comparable specifications. Those

listed are for guidance. The RMS ripple current rating and

ESR are the critical parameters necessary to insure both opti-

mum regulator performance and long capacitor life.

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