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參數(shù)資料
| 型號： | SP7648ER |
| 英文描述： | Low Reference High Efficiency Boost Regulator |
| 中文描述： | 高效率低參考升壓穩(wěn)壓器 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 236K |
| 代理商： | SP7648ER |
6
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator Copyright 2005 Sipex Corporation
THEORY OF OPERATION
Figure 1. Inductor Current vs. Load
At light loads (as shown in plot A in Figure 1)
the charge cycle will last the maximum value
for
t
ON
: For a 3V battery this would be as
follows: T
ON
= K
ON
/ V
BATT
= 3.5V
μ
S/ 3V =
1.17
μ
S. The current built up in the coil during
the charge cycle gets fully discharged in the
discontinuous conduction mode (DCM).
When the current in the coil has reached
zero, the synchronous rectifier switch is
opened and the voltage across the coil (from
V
BATT
to LX) is shorted internally to eliminate
inductive ringing. With increasing load (as
shown in plot B in Figure 1) this inductor
damping time becomes shorter, because
the output will quickly drop below its regula-
tion point due to heavier load. If the load
current increases further, the SP7648 en-
ters continuous conduction mode (CCM)
where there is always current flowing in the
inductor. The charge time remains at maxi-
mum T
ON
as long as the inductor peak
current limit is not reached as shown in plot
C in Figure 1. The inductor peak current limit
can be programmed by tying a resistor R
LIM
from the R
LIM
pin to ground where:
I
PEAK
= 1600 / R
LIM
When the peak current limit is reached the
charge time is short-cycled. In plot D of
Figure 1, the switch current reaches the
peak current limit during the charge period
which ends the charge cycle and starts the
discharge cycle. However, full load is not yet
achieved because at the end of the mini-
mum discharge time the output was still
within regulation. Maximum load is reached
when this discharge time has shrunk to the
minimum allowed value T
OFF
as shown in
Plot E of Figure 1.
_____________________ COMPONENT
SELECTION
Selection of capacitors for SP7648 power
supply circuits can be made through the use
of the Component Selection Table. Capaci-
tor equivalent series resistance (ESR) in the
range of 0.2 to 0.3
is a requirement for
obtaining sufficient output voltage ripple for
the SP7648 to properly regulate under its
load. For example, in the SP7648 applica-
tion circuit a 10
μ
F, 10V, X5R, surface mount
ceramic output filter capacitor is used.
Ceramic capacitors have an ESR too low to
produce enough output ripple for the SP7648
to regulate the output; therefore, a 0.33
resistor is added in series with the 10
μ
F
capacitor at the V
OUT
pin. Designers should
select input and output capacitors with a
rating exceeding the inductor current ripple,
which is typically set by the inductor value
and the K
ON
value as given in the following
relationship:
I
L(RIPPLE)
= K
ON
/L, where K
ON
= 3.5V*
μ
S
Inductor Current vs. Load
Ton Max.
Toff Min.
E. Iripple=Toff* (Vo
- Vi)/L
llim
llim
llim
llim
llim
Ton Max.
Ton Max.
Ton Max.
Ton Max.
Toff Min.
D. Toff*= (Vo
- Vi)/L<Iripple<Ton*Vi/L
Toff Min.
Toff Min.
Toff Min.
C. Iripple=Ton*Vi/L
B. Iripple=Ton*Vi/L
A. Iripple=Ton*Vi/L
E
D
C
B
A
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SP7648EU | Low Reference High Efficiency Boost Regulator |
| SP7648TR | Low Reference High Efficiency Boost Regulator |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP7648ER/TR | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:PackageLow Reference High efficiency Boost Regulator |
| SP7648ER-L | 功能描述:LED照明驅(qū)動器 Efficiency Boost Regulator RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風格:SMD/SMT 封裝 / 箱體:SO-16N |
| SP7648ER-L/TR | 功能描述:DC/DC 開關(guān)控制器 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 |
| SP7648EU | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP7648EU/TR | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Reference High Efficiency Boost Regulator |
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