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参数资料
| 型号： | PTN78000WAZ |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 电源模块 |
| 英文描述： | 1-OUTPUT 22.5 W DC-DC REG PWR SUPPLY MODULE |
| 封装： | ROHS COMPLIANT, DIP-5 |
| 文件页数： | 13/25页 |
| 文件大小： | 668K |
| 代理商： | PTN78000WAZ |
Optional Input/Output Filters
Input/Output Capacitors
PTN78000W
2
5
+
4
GND
A
B
1
3
GND
UDG05086
VO
VI
VO
VI
Inhibit
C1
2.2
F
50 V
Ceramic
C2
2.2
F
50 V
Ceramic
(Required)
C3
100
F
(Required)
C4
2.2
F
Ceramic
RSET
VOAdjust
π Filters
SLTS230B – NOVEMBER 2004 – REVISED OCTOBER 2007 .......................................................................................................................................... www.ti.com
Power modules include internal input and output ceramic capacitors in all their designs. However, some
applications require much lower levels of either input reflected or output ripple/noise. This application note
describes various filters and design techniques found to be successful in reducing both input and output
ripple/noise.
The easiest way to reduce output ripple and noise is to add one or more 1-F ceramic capacitors, such as C4
shown in Figure 31. Ceramic capacitors should be placed close to the output power terminals. A single 1-F
capacitor reduces the output ripple/noise by 10% to 30% for modules with a rated output current of less than 3 A.
(Note: C3 is recommended to improve the regulators transient response and does not reduce output ripple and
noise.)
Switching regulators draw current from the input line in pulses at their operating frequency. The amount of
reflected (input) ripple/noise generated is directly proportional to the equivalent source impedance of the power
source including the impedance of any input lines. The addition of C1, minimum 1-F ceramic capacitor, near the
input power pins, reduces reflected conducted ripple/noise by 30% to 50%.
Figure 31. Adding High-Frequency Bypass Capacitors To The Input and Output
If a further reduction in ripple/noise level is required for an application, higher order filters must be used. A
π (pi)
filter, employing a ferrite bead (Fair-Rite part number 2673000701 or equivalent) in series with the input or output
terminals of the regulator reduces the ripple/noise by at least 20 db (see Figure 32 and Figure 33). In order for
the inductor to be effective in reduction of ripple and noise ceramic capacitors are required. (Note: see Capacitor
Recommendations for the PTN78000W for addtional information on vendors and component suggestions.)
These inductors plus ceramic capacitors form an excellent filter because of the rejection at the switching
frequency (650 kHz - 1 MHz). The placement of this filter is critical. It must be located as close as possible to the
input or output pins to be efffective. The ferrite bead is small (12,5 mm x 3 mm), easy to use, low cost, and has
low dc resistance. Fair-Rite also manufactures a surface-mount bead (part number 2773021447), through hole
(part number 2673000701) rated to 5 A, but in this application, it is effective to 5 A on the output bus. Inductors
in the range of 1 H to 5 H can be used in place of the ferrite inductor bead.
20
Copyright 2004–2007, Texas Instruments Incorporated
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| PTN78020AAS | 功能描述:DC/DC转换器 4A Wide Inp/Neg Out Adj Module RoHS:否 制造商:Murata 产品: 输出功率: 输入电压范围:3.6 V to 5.5 V 输入电压（标称）: 输出端数量:1 输出电压（通道 1）:3.3 V 输出电流（通道 1）:600 mA 输出电压（通道 2）: 输出电流（通道 2）: 安装风格:SMD/SMT 封装 / 箱体尺寸: |
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