For technical support and more information, see inside back cover or visit www.ti.com

Table 1: Input/Output Capacitors

N/R –Not recommended. The voltage rating does not meet the minimin operating limits.

Capacitor Recommendations for

the

Dual-Output PT6980 Regulator Series

Input Capacitors:

The recommended input capacitance is determined by 1.0

ampere minimum ripple current rating and 330µF minimum

capacitance . Ripple current and <100m

Ω equivalent se-

ries resistance (ESR) values are the major considerations,

along with temperature, when designing with different

types of capacitors. Tantalum capacitors have a recommended

minimum voltage rating of 2

× the maximum DC voltage +

AC ripple. This is necessary to insure reliability for input

voltage bus applications

than 50m

Ω. Electrolytic capacitors have poor ripple per-

formance at frequencies greater than 400kHz but excellent

low frequency transient response. Above the ripple fre-

quency, 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

have an ESR of up to 200m

Ω for optimum performance

and ripple reduction. (Note: Vendor part numbers for the

PT6980 Series

Tantalum Capacitors

Tantalum type capacitors may be used at the output, but

only the AVX TPS series, Sprague 593D/594/595 series,

or Kemet T495/T510 series. The AVX TPS series, Kemet

or Sprague series tantalums are recommended over many

other 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 also less reliable than

the AVX TPS series when determining power dissipation

capability. Tantalum or Oscon® types are recommended

for applications where ambient temperatures fall below 0°C.

Capacitor Table

Table 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

(Equivalent Series Resistance at 100kHz) are critical parameters

necessary to insure both optimum regulator performance and

long capacitor life.

Application Notes

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