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參數(shù)資料
| 型號(hào)： | SC471 |
| 廠商： | Semtech Corporation |
| 英文描述： | Synchronous Buck Controller with Multi-Level VOUT Transition Support |
| 中文描述： | 同步降壓控制器具有多層次VOUT電源支持過渡 |
| 文件頁數(shù)： | 13/27頁 |
| 文件大?。?/td> | 634K |
| 代理商： | SC471 |
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13
2006 Semtech Corp.
SC471/SC471A
www.semtech.com
POWER MANAGEMENT
Applications Information
(continued)
V
OUT
FB
R1
R2
D0/D1
D0/D1
RTN
750mV
(FB threshold)
FB
DH
DL
Final
VOUT
Initial
VOUT
Voltage overshoot
VOUT
R3/R4
Figure 8
The overshoot can be approximated by the following
equation, where ICL is the current limit, V
is the desired
setpoint for the
fi
nal voltage, L is in
μ
H and COUT is in
μ
F.
V
MAX
=
√
( ICL
2
* L/C
OUT
+ V
FINAL
2
)
This overshoot can be eliminated by using a small RC
circuit to smooth the voltage seen at FB, see Figure 9.
The presence of Rs/Cs will prevent the rapid changes at
D0/D1 from moving FB too quickly. The result is a gradual
change from VOUT
to VOUT
, which prevents the
build-up of high inductor current and reduces overshoot.
Note: Cs can be connected to either VOUT or GND. VOUT is
preferred because this results in higher ripple seen at the FB
pin, which improves stability.
RTN
750mV
(FB threshold)
FB
DH
DL
Final
VOUT
Initial
VOUT
VOUT
V
OUT
FB
R1
R2
RS
CS
VS
D0/D1
R3/R4
D0/D1
CS
Figure 9
Note: that Rs/Cs are part of the FB resistor divider and therefore
affect the output voltage sensing. To minimize the effect of
this, select Rs and Cs according to the following guidelines:
The total of Rs + R3/R4 should be chosen to give the
correct total resistance needed to adjust VOUT. Set RS
= R3/R4.
Cs should be chosen to give a time constant equal to
approximately 18
μ
sec for 325 kHz operation. Note that
Cs is charging through a resistive network composed of
Rs/R1/R2/R3/R4. The effective resistance seen by Cs
is equal to the parallel combination of (R1 + Rs) and R3
or R4. For example, if the values for R1/R2/Rs/R3 are
10K/50K/18.7K/18.7K, then the effective resistance for
(10K + 18.7K) paralleled with 18.7K, which is 11.2K. To
set a time constant of 18
μ
sec, CS should be approximately
18
μ
sec/11.2k = 1600pF.
相關(guān)PDF資料 |
PDF描述 |
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| SC471A | Synchronous Buck Controller with Multi-Level VOUT Transition Support |
| SC471AMLTRT | Synchronous Buck Controller with Multi-Level VOUT Transition Support |
| SC472B | Single-Phase Single Chip Graphics Core Power Supply |
| SC473 | Single-Phase Single Chip Graphics Core Power Supply |
| SC473EVB | Single-Phase Single Chip Graphics Core Power Supply |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC471_08 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Synchronous Buck Controller with Multi-Level VOUT Transition Support |
| SC471A | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Synchronous Buck Controller with Multi-Level VOUT Transition Support |
| SC471AEVB | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Synchronous Buck Controller with Multi-Level VOUT Transition Support |
| SC471AMLTRT | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Synchronous Buck Controller with Multi-Level VOUT Transition Support |
| SC471EVB | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Synchronous Buck Controller with Multi-Level VOUT Transition Support |
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