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Application Notes
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ATH15T033 & ATH15T05 Series
Table 2-1: Recommended Input/Output Capacitors
ATH15T033/T05: Capacitor Recommendations
Input Capacitor
The recommended input capacitor(s) is determined by
the 470 μF minimum capacitance, and 700 mA rms mini-
mum ripple current rating.
Ripple current and <100 m
equivalent series resistance
(ESR) values are the major considerations, along with
temperature, when designing with different types of capaci-
tors. Tantalum capacitors have a recommended minimum
voltage rating of twice
2
×
(the maximum DC voltage +
AC ripple). This is standard practice for tantalum capaci-
tors to insure reliability.
Output Capacitors (Optional)
The recommended ESR of the capacitors is equal to or
less than 150 m
. 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. Preferred low-ESR type capacitor
part numbers are identified in Table 2-1.
Tantalum Capacitors
Tantalum type capacitors can be used for the output but
only the AVX TPS, Sprague 593D/594/595 or Kemet
T495/T510 series. These capacitors are recommended
over many other tantalum types due to their higher rated
surge, power dissipation, and ripple current capability.
As a caution, the TAJ series by AVX is not recommended.
This series has considerably higher ESR, reduced power
dissipation, and lower ripple current capability. The TAJ
series is less reliable than the AVX TPS series when deter-
mining power dissipation capability. Tantalum, ceramic or
Os-con types are recommended for applications where
ambient temperatures fall below 0 °C.
Ceramic capacitors may be substituted for electrolytic
types with the minimum capacitor value for improved
ripple reduction on the input and output bus.
Capacitor Table
Table 1 identifies the characteristics of capacitors from a
number of vendors with acceptable ESR and ripple cur-
rent (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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