欢迎访问ic37.com |
会员登录 免费注册
发布采购

RT9168 参数 Datasheet PDF下载

RT9168图片预览
型号: RT9168
PDF下载: 下载PDF文件 查看货源
内容描述: 200毫安/ 500毫安固定输出电压LDO稳压器 [200mA/500mA Fixed Output Voltage LDO Regulator]
分类和应用: 稳压器单个低压差线性稳定器
文件页数/大小: 11 页 / 155 K
品牌: RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
 浏览型号RT9168的Datasheet PDF文件第3页浏览型号RT9168的Datasheet PDF文件第4页浏览型号RT9168的Datasheet PDF文件第5页浏览型号RT9168的Datasheet PDF文件第6页浏览型号RT9168的Datasheet PDF文件第8页浏览型号RT9168的Datasheet PDF文件第9页浏览型号RT9168的Datasheet PDF文件第10页浏览型号RT9168的Datasheet PDF文件第11页  
RT9168/A  
Application Information  
Region of Stable Cout ESR v.s Load Current  
100  
Capacitor Selection and Regulator Stability  
Unstable Region  
Stable Region  
COUT = 4.7uF  
COUT = 1uF  
Like any low-dropout regulator, the external capacitors used  
with the RT9168/A must be carefully selected for regulator  
stability and performance.  
10  
1
Using a capacitor whose value is > 1μF on the  
RT9168/A input and the amount of capacitance can be  
increased without limit. The input capacitor must be  
located 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.  
0.1  
Unstable Region  
0.01  
0.001  
0
40  
80  
120  
160  
200  
Load Current (mA)  
Figure 1  
The output capacitor must meet both requirements for  
minimum amount of capacitance and ESR in all LDO  
applications. The RT9168/A is 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 RT9168/A output ensures stability. The  
RT9168/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 capacitor should be located not more than  
0.5" from the VOUT pin of the RT9168/Aand returned to a  
clean analog ground.  
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.  
Load-Transient Considerations  
The RT9168/Aload-transient response graphs (see Typical  
Operating Characteristics) show two components of the  
output response: a DC shift from the output impedance  
due to the load current change, and the transient response.  
The DC shift is quite small due to the excellent load  
regulation of the IC. Typical output voltage transient spike  
for a step change in the load current from 0mAto 50mAis  
tens mV, depending on the ESR of the output capacitor.  
Increasing the output capacitor's value and decreasing the  
ESR attenuates the overshoot.  
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.  
Shutdown Input Operation  
The RT9168/A is shutdown by pulling the EN input low,  
and turned on by driving the input high. If this feature is  
not to be used, the EN input should be tied to VIN to  
keep the regulator on at all times (the EN input must not  
be left floating).  
DS9168/A-15 March 2007  
www.richtek.com  
7