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參數(shù)資料
| 型號： | sp6650 |
| 英文描述： | High Efficiency 600mA Synchronous Buck Regulator(高效率,600mA同步補償穩(wěn)壓器) |
| 中文描述： | 600mA的高效率同步降壓穩(wěn)壓器（高效率，600mA的同步補償穩(wěn)壓器） |
| 文件頁數(shù)： | 11/17頁 |
| 文件大小： | 170K |
| 代理商： | SP6650 |
11
Rev. 2/4/02
SP6650 High Efficiency 600mA Synchronous Buck Regulator
Copyright 2002 Sipex Corporation
External Component Selection
Inductor
According to the pulse frequency modulation
(PFM) algorithm, the peak to peak output ripple
current can be calculated as:
I
LR
≈
K
ON
L
K
ON
= 2.7
μ
s*V is a constant for SP6650 and is
set by the parameters of the internal ON-time
calculation circuitry. For the recommended 22
μ
H
inductor, typical ripple currents are I
LR
= 123mA
in discontinuous conduction mode (DCM) op-
eration. During continuous conduction mode,
the speed of the loop comparator determines the
current ripple. It is approximately equal to 200mA
with a 22
μ
H inductor.
The value of the inductor is chosen based on the
constant K
ON
and acceptable current ripple. Two
additional inductor parameters are important: its
current rating and its DC resistance.
When the current through the inductor reaches
the level of I
sat
, inductance drops down to 70%
from the nominal. This non-linear change can
cause stability problems or excessive fluctuation
in current ripple. To avoid this, the inductor
should be chosen with saturation current at least
equal to the maximum output current of the
converter plus half of the ripple. To provide the
best converter performance in dynamic condi-
tions such as start-up and load transients, induc-
tors with saturation current close to the chosen
I
LIM
are recommended.
The second important inductor parameter, DC
resistance, directly defines the efficiency of the
converter, therefore, the inductor should be cho-
sen with the minimum possible DC resistance
for a particular design. Recommended types of
the inductors for different applications are given
in Table 1. Preferred inductors for on board
power supplies with the SP6650 converter are
shielded inductors to minimize radiated mag-
netic fields emissions.
APPLICATION INFORMATION
All components recommended for typical de-
signs like those shown in the applications sche-
matics are given in Table 1.
Input and Output Capacitors
Output capacitor is often selected based on the
requirement on the output ripple voltage. In a
Buck regulator, the output ripple is determined
by ESR (equivalent series resistor) of the output
capacitors and inductor ripple current
V
OR
= ESR * I
LR
,
where V
OR
= peak to peak output ripple voltage.
SP6650’s adaptive on-time scheme provides a
constant inductor ripple that is independent of
input voltages and thus makes it easier to select
the output capacitor. In many power supply
designs, the ripple voltage needs to be less than
3% of the DC output voltage. Using low ESR
tantalum or electrolytic capacitors to reduce the
output ripple.
Due to the nature of the PFM control, certain
output ripple is required for stable operation.
The loop comparator requires minimum of 15mV
ripple on the FB pin to reliably toggle the com-
parator output. That translates to an output ripple
of
V
OR(MIN)
= 15mV * V
OUT
V
REF
where V
REF
= 1.25V is the internal reference
voltage.
To reduce the output ripple and improve stabil-
ity, a small capacitor can be paralleled with the
feedback voltage divider as shown on page 1
.
This capacitor forms a high pass filter with
feedback resistor to increase the ripple voltage
seen by the FB pin. The value of the capacitor
should be in the range of 100pF to 500pF.
Although the 3.3V output can be programmed
simply by connecting the FB pin to the ground,
using this external feedback scheme can signifi-
cantly reduce the output ripple. For output ripple
less than 15mV, for instance when ceramic
capacitors are used, an artificial ramp can be
generated and superimposed onto the output.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP6650EB | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP6650EU | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP6650EU/TR | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:High Efficiency 600mA Synchronous Buck Regulator Ideal for portable designs powered with Li Ion battery |
| SP6650EU-L | 功能描述:DC/DC 開關(guān)控制器 High Eff 600mA Synchronous RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| SP6650EU-L/TR | 功能描述:DC/DC 開關(guān)控制器 High Eff 600mA Synchronous RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
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