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RT9167A-16PB 参数 Datasheet PDF下载

RT9167A-16PB图片预览
型号: RT9167A-16PB
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, 300毫安/ 500毫安LDO稳压器 [Low-Noise, Fixed Output Voltage,300mA/500mA LDO Regulator]
分类和应用: 稳压器
文件页数/大小: 13 页 / 231 K
品牌: RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
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RT9167/A  
Application Information  
Capacitor Selection and Regulator Stability  
capacitor should be located not more than 0.5" from the  
VOUT pin of the RT9167/A and returned to a clean analog  
ground.  
Like any low-dropout regulator, the external capacitors used  
with the RT9167/A must be carefully selected for regulator  
stability and performance.  
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.  
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.  
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.  
The output capacitor must meet both requirements for  
minimum amount of capacitance and ESR in all LDOs  
application. The RT9167/Ais designed specifically to work  
with low ESR ceramic output capacitor in space-saving  
and performance consideration. Using a ceramic capacitor  
whose value is at least 1μF with ESR is > 5mΩ on 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. Figure 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  
Use a 10nF bypass capacitor at BP for low output voltage  
noise. The capacitor, in conjunction with an internal 200kΩ  
resistor, 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  
200kΩ resistor. Figure 2 shows the power on response.  
Region of Stable COUT ESR vs. Load Current  
100  
COUT = 1uF  
Unstable Region  
Stable Region  
CBP = 10nF  
10  
CBP = 10nF  
1
0.1  
Unstable Region  
0.01  
0.001  
VOUT = 3.0V  
0
50  
100  
150  
200  
250  
300  
0
5.0  
Time (ms)  
10.0  
15.0  
Load Current (mA)  
Figure 1  
Figure 2  
www.richtek.com  
8
DS9167/A-26 March 2007