PT6341 Datasheet, PDF (5/9 Pages) Texas Instruments – 6-A 12-V Input Adjustable Integrated Switching Regulator

Application Notes
PT6340 Series
Capacitor Recommendations for the PT6340
6A Excalibur™ Regulator Series
Input Capacitors:
Output Current ≤4A Continuous (Table 1)
The recommended input capacitance is determined by
740 milli-amperes (rms) minimum ripple current rating,
less than 100mΩ ESR (equivalent series resistance),
and 100µF minimum capacitance. The ripple current
rating, ESR, and operating temperature are the major
considerations when selecting the input capacitor.
It is recommended that tantalum capacitors have a
minimum voltage rating of twice (2×) the maximum dc
voltage, plus the ac ripple. This is necessary to insure
reliability with 12V input voltage bus applications. None
of the 100µF tantalum capacitors were found to meet
this requirement.
Input Capacitors:
Output Current >4A Continuous (Table 2)
The recommended input capacitance is determined by
1.0 amperes (rms) minimum ripple current rating and
100µF minimum capacitance. The ripple current rating,
combined with less than 100mΩ ESR (equivalent series
resistance) value are the major considerations, along
with temperature, when selecting the input capacitor.
It is recommended that tantalum capacitors have a
minimum voltage rating of twice (2×) the maximum dc
voltage, plus the ac ripple. This is necessary to insure
reliability for 12V input voltage bus applications. None
of the 100µF tantalum capacitors were found to meet
this requirement.
Output Capacitors:
Output Current 0–6A (Table 1 & Table 2)
The ESR of the required capacitor must be less than,
or equal to 50mΩ. Electrolytic capacitors have poor
ripple performance at frequencies greater than 400kHz
but excellent low frequency transient response. Above
the ripple frequency, ceramic decoupling 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’s part numbers are identified in the capacitor
tables.
Tantalum Capacitors
Tantalums are acceptable on the output bus but only the
AVX TPS series, Sprague 593D/594/595 series or Kemet
T495/T510 series. These capacitors 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 exhibits considerably higher ESR and lower ripple
current capability. The TAJ series is also less reliable than
the TPS series when determining power dissipation
capability. Tantalum or Oscon capacitor types are recom-
mended for applications where ambient temperatures fall
below 0°C.
Capacitor Tables
Table 1 and Table 2 identify the vendors with acceptable
ESR and maximum allowable ripple current (rms) ratings.
The output capacitors are identified in both tables under
the “Output Bus” column with the required quantity.
The input capacitors are listed in both tables. Table 1 has
the recommended input capacitors when operating the
ISR at a load current of 4Adc or less, and Table 2 identi-
fies input capacitors for ISR load currents greater than
4Adc.
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.
For technical support and more information, see inside back cover or visit www.ti.com