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RT9167A-50CS 参数 Datasheet PDF下载

RT9167A-50CS图片预览
型号: RT9167A-50CS
PDF下载: 下载PDF文件 查看货源
内容描述: 低噪声固定输出电压200MA / 500MA LDO稳压器 [LOW NOISE FIXED OUTPUT VOLTAGE 200MA/500MA LDO REGULATOR]
分类和应用: 稳压器输出元件
文件页数/大小: 14 页 / 257 K
品牌: ETC [ ETC ]
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RT9167/A  
Applications Guides  
Capacitor Selection and Regulator Stability  
Region of Stable C  
ESR vs. Load Current  
OUT  
100  
Like any low-dropout regulator, the external capacitors  
used with the RT9167/A must be carefully selected for  
regulator stability and performance.  
C
= 4.7µF  
OUT  
10  
C
= 1µF  
OUT  
Using a capacitor whose value is > 1µF on the  
RT9167/A input and the amount of capacitance can be  
increased without limit. The input capacitor must be  
located a distance of not more than 0.5" from the input  
pin of the IC and returned to a clean analog ground.  
Any good quality ceramic or tantalum can be used for  
this capacitor. The capacitor with larger value and  
lower ESR (equivalent series resistance) provides  
better PSRR and line-transient response.  
1
0.1  
0.01  
0.001  
0
40  
80  
120  
160  
200  
Load Current (mA)  
Fig. 1  
The output capacitor must meet both requirements for  
minimum amount of capacitance and ESR in all LDOs  
application. The RT9167/A is designed specifically to  
work with low ESR ceramic output capacitor in space-  
Note that some ceramic dielectrics exhibit large  
capacitance and ESR variation with temperature. It  
may be necessary to use 2.2µF or more to ensure  
stability at temperatures below -10°C in this case. Also,  
tantalum capacitors, 2.2µF or more may be needed to  
maintain capacitance and ESR in the stable region for  
strict application environment.  
saving and performance consideration. Using  
a
ceramic capacitor whose value is at least 1uF with  
ESR is > 5mon the RT9167/A output ensures  
stability. The RT9167/A still works well with output  
capacitor of other types due to the wide stable ESR  
range. Fig.1 shows the curves of allowable ESR range  
as a function of load current for various output  
voltages and capacitor values. Output capacitor of  
larger capacitance can reduce noise and improve  
load-transient response, stability, and PSRR. The  
output capacitor should be located not more than  
Tantalum capacitors maybe suffer failure due to surge  
current when it is connected to a low-impedance  
source of power (like a battery or very large capacitor).  
If a tantalum capacitor is used at the input, it must be  
guaranteed to have a surge current rating sufficient for  
the application by the manufacture.  
0.5" from the V  
to a clean analog ground.  
pin of the RT9167/A and returned  
OUT  
Use a 10nF bypass capacitor at BP for low output  
voltage noise. The capacitor, in conjunction with an  
internal 200Kresistor, which connects bypass pin  
and the band-gap reference, creates an 80Hz low-  
pass filter for noise reduction. Increasing the  
capacitance will slightly decrease the output noise,  
but increase the start-up time. The capacitor  
connected to the bypass pin for noise reduction must  
have very low leakage. This capacitor leakage  
current causes the output voltage to decline by a  
proportional amount to the current due to the voltage  
drop on the internal 200Kresistor. Fig. 2 shows the  
power on response.  
www.richtek-ic.com.tw  
DS9167/A-10 July 2001  
8
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