參數(shù)資料
型號(hào): PTH08000WAZT
廠商: TEXAS INSTRUMENTS INC
元件分類: 電源模塊
英文描述: 1-OUTPUT DC-DC REG PWR SUPPLY MODULE
封裝: ROHS COMPLIANT, DIP-6
文件頁數(shù): 20/20頁
文件大?。?/td> 661K
代理商: PTH08000WAZT
www.ti.com
CAPACITOR RECOMMENDATIONS FOR THE PTH08000W WIDE-OUTPUT ADJUST
Input Capacitor
Output Capacitors (Optional)
Ceramic Capacitors
Tantalum Capacitors
Capacitor Table
SLTS248B – JUNE 2005 – REVISED FEBRUARY 2008
POWER MODULES
The minimum required input capacitor is 100 F of capacitance. When VO > 3.4 V, the 100-F electrolytic
capacitance must be rated for 650-mArms ripple current . For VO < 3.4 V, the ripple current rating must be at
least 500 mArms. The ripple current rating of electrolytic capacitors is a major consideration when they are used
at the input.
When specifying regular tantalum capacitors for use at the input, a minimum voltage rating of 2
× (maximum dc
voltage + ac ripple) is highly recommended. This is standard practice to ensure reliability. Polymer-tantalum
capacitors are not affected by this requirement.
For improved ripple reduction on the input bus, ceramic capacitors can also be added to complement the
required electrolytic capacitance.
No output capacitance is required for normal operation. However, applications with load transients (sudden
changes in load current) can benefit by adding external output capacitance. A 100-F electrolytic or ceramic
capacitor can be used to improve transient response. Adding a 100-F nonceramic capacitor allows the module
to meet its transient response specification. A high-quality computer-grade electrolytic capacitor should be
adequate.
Electrolytic capacitors should be located close to the load circuit. These capacitors provide decoupling over the
frequency range, 2 kHz to 150 kHz. Aluminum electrolytic capacitors are suitable for ambient temperatures
above 0
°C. For operation below 0°C, tantalum or Os-Con-type capacitors are recommended. When using one or
more nonceramic capacitors, the calculated equivalent ESR should be no lower than 10m
(14m using the
manufacturer's maximum ESR for a single capacitor). A list of preferred low-ESR-type capacitors are identified in
Above 150 kHz, the performance of aluminum electrolytic capacitors becomes less effective. To further improve
the reflected input ripple current, or the output transient response, multilayer ceramic capacitors must be added.
Ceramic capacitors have low ESR and their resonant frequency is higher than the bandwidth of the regulator.
When placed at the output, their combined ESR is not critical as long as the total value of ceramic capacitance
does not exceed 220 F. Also, to prevent the formation of local resonances, do not exceed the maximum
number of capacitors specified in the capacitor table.
Additional tantalum-type capacitors can be used at both the input and output, and are recommended for
applications where the ambient operating temperature can be less than 0
°C. The AVX TPS, Sprague
593D/594/595, and Kemet T495/T510/T520 capacitors series are suggested over many other tantalum types due
to their rated surge, power dissipation, and ripple current capability. As a caution, many general-purpose
tantalum capacitors have considerably higher ESR and lower ripple current capability. These capacitors are also
less reliable as they have lower power dissipation capability and surge current ratings. Tantalum capacitors that
do not have a stated ESR or surge current rating are not recommended for power applications. When specifying
Os-Con and polymer-tantalum capacitors for the output, the minimum ESR limit is encountered well before the
maximum capacitance value is reached.
The capacitor table, Table 3, identifies the characteristics of capacitors from a number of vendors with
acceptable ESR and ripple current (rms) ratings. The recommended 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 rating
and ESR (at 100 kHz) are critical parameters necessary to ensure both optimum regulator performance and long
capacitor life.
Copyright 2005–2008, Texas Instruments Incorporated
9
Product Folder Link(s) :PTH08000W
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