參數(shù)資料
型號: R1230D201G-TR
廠商: RICOH COMPANY LTD
元件分類: 穩(wěn)壓器
英文描述: SWITCHING REGULATOR, 575 kHz SWITCHING FREQ-MAX, PDSO8
封裝: 0.9 MM HEIGHT, SON-8
文件頁數(shù): 5/26頁
文件大?。?/td> 284K
代理商: R1230D201G-TR
R1230D
13
How to Adjust Output Voltage and about Phase Compensation
As for Adjustable Output type, feedback pin (VFB) voltage is controlled to maintain 0.8V.
Output Voltage, VOUT is as following equation;
VOUT: R1+R2 = VFB: R2
VOUT = VFB × (R1 + R2)/R2
Thus, with changing the value of R1 and R2, output voltage can be set in the specified range.
In the DC/DC converter, with the load current and external components such as L and C, phase might be behind 180
degree. In this case, the phase margin of the system will be less and stability will be worse. To prevent this, phase
margin should be secured with proceeding the phase. A pole is formed with external components L and COUT.
OUT
LC
1/2
~
Fpole
π
A zero (signal back to zero) is formed with R1 and Cb.
Fzero ~ 1/(2π×R1×Cb)
First, choose the appropriate value of R1, R2 and Cb.
Set R1+R2 value 100k or less.
For example, if L = 10H, COUT = 10F, the cut off frequency of the pole is approximately 16kHz.
To make the cut off frequency of the pole higher than 16kHz, set R1 = 42k and Cb = 100pF.
If VOUT is set at 1.5V, R2 = 48k is appropriate.
If a ceramic capacitor is desirable as COUT in your application, nonetheless of the usage of both the fixed output voltage
type and adjustable output type, add 0.2 or more resistance to compensate the ESR. Further, if a ceramic capacitor is
desirable to use as COUT without adding another resister to compensate the ESR, phase should be back drastically. To
make it, R2 value should be smaller compared to R1. As a result, the set output voltage may be large. For example, to
make VOUT = 1.5V, constants are R1 = 42k, R2 = 48k, and Cb = 100pF. If the ceramic capacitor is used, under the
heavy load condition, oscillation may be result. On the other hand, if R2 = 12k and VOUT = 3.6V, phase back becomes
also large, and even if the device is used with a heavy load, the operation will be stable.
Rb is effective for reducing the noise on VFB, however, it is not always necessary. If it is necessary, use as much as
30k as Rb.
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