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RT8223P 参数 Datasheet PDF下载

RT8223P图片预览
型号: RT8223P
PDF下载: 下载PDF文件 查看货源
内容描述: 高效率,主电源控制器,用于笔记本电脑 [High Efficiency, Main Power Supply Controller for Notebook Computer]
分类和应用: 电脑控制器
文件页数/大小: 23 页 / 311 K
品牌: RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
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RT8223P  
Table 3. Power Up Sequencing  
EN  
(V)  
ENC  
(V)  
ENTRIP1  
ENTRIP2  
REF  
Off  
VREG5 VREG3  
SMPS1  
SMPS2  
Off  
Low  
Low  
Low  
X
X
X
X
Off  
On  
Off  
On  
Off  
Off  
“>2.4V”  
=> High  
On  
Off  
“>2.4V”  
=> High  
“>2V”  
Off  
Off  
On  
On  
Off  
On  
Off  
On  
On  
On  
On  
On  
On  
On  
On  
On  
On  
On  
On  
On  
Off  
Off  
On  
On  
Off  
On  
Off  
On  
=> High  
“>2.4V”  
=> High  
“>2V”  
=> High  
“>2.4V”  
=> High  
“>2V”  
=> High  
“>2.4V”  
=> High  
“>2V”  
=> High  
Output Voltage Setting (FBx)  
where LIR is the ratio of the peak to peak ripple current to  
the average inductor current.  
Connect a resistor voltage-divider at the FBxpin between  
VOUTx and GND to adjust the respective output voltage  
between 2V and 5.5V (Figure 4). Referring to Figure 4 as  
an example, choose R2 to be approximately 10kΩ, and  
solve for R1 using the equation :  
Find a low-loss inductor having the lowest possible DC  
resistance that fits in the allotted dimensions. Ferrite cores  
are often the best choice, although powdered iron is  
inexpensive and can work well at 200kHz. The core must  
be large enough not to saturate at the peak inductor current  
(IPEAK) :  
R1 ⎞  
V
= V  
× 1+  
OUTX  
FBX  
⎟⎟  
R2  
where VFBX is 2V.  
IPEAK = ILOAD(MAX) + (LIR/2)×ILOAD(MAX)  
V
IN  
The calculation above shall serve as a general reference.  
To further improve the transient response, the output  
inductance can be reduced even further. This needs to be  
considered along with the selection of the output capacitor.  
V
OUTx  
UGATEx  
PHASEx  
LGATEx  
R1  
R2  
VOUTx  
FBx  
Output Capacitor Selection  
The capacitor value and ESR determine the amount of  
output voltage ripple and load transient response. Thus,  
the capacitor value must be greater than the largest value  
calculated from below equations :  
Figure 4. Setting VOUTX with a Resistor VoltageDivider  
VOUTx  
(ΔILOAD )2 ×L×(K×  
+ tOFF(MIN)  
)
Output Inductor Selection  
V
IN  
VSAG  
=
The switching frequency (on-time) and operating point (%  
ripple or LIR) determine the inductor value as shown in  
the following equation :  
VIN VOUTx  
2×COUT × VOUTx × K×  
t  
OFF(MIN)  
V
IN  
(ΔILOAD)2 ×L  
2×COUT × VOUTx  
tON ×(VIN VOUTx  
LIR×ILOAD(MAX)  
)
VSOAR  
=
L =  
DS8223P-01 June 2011  
www.richtek.com  
21  
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