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參數(shù)資料
| 型號： | EL7585ILZ |
| 廠商： | INTERSIL CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | TFT-LCD Power Supply |
| 中文描述： | 3.5 A SWITCHING REGULATOR, 1100 kHz SWITCHING FREQ-MAX, QCC20 |
| 封裝： | 4 X 4 MM, ROHS COMPLIANT, MO-220, QFN-20 |
| 文件頁數(shù)： | 11/18頁 |
| 文件大?。?/td> | 732K |
| 代理商： | EL7585ILZ |
11
FN7345.1
July 1, 2005
Cascaded MOSFET Application
A 20V N-channel MOSFET is integrated in the boost
regulator. For the applications where the output voltage is
greater than 20V, an external cascaded MOSFET is needed
as shown in Figure 22. The voltage rating of the external
MOSFET should be greater than V
BOOST
.
Linear-Regulator Controllers (V
ON
, V
LOGIC
, and
V
OFF
)
The EL7585 includes three independent linear-regulator
controllers, in which two are positive output voltage (V
ON
and V
LOGIC
), and one is negative. The V
ON
, V
OFF
, and
V
LOGIC
linear-regulator controller functional diagrams,
applications circuits are shown in Figures 23, 24, and 25
respectively.
Calculation of the Linear Regulator Base-Emitter
Resistors (R
BL
, R
BP
and R
BN
)
For the pass transistor of the linear regulator, low frequency
gain (Hfe) and unity gain freq. (f
T
) are usually specified in the
datasheet. The pass transistor adds a pole to the loop
transfer function at f
p
=f
T
/Hfe. Therefore, in order to maintain
phase margin at low frequency, the best choice for a pass
device is often a high frequency low gain switching
transistor. Further improvement can be obtained by adding a
base-emitter resistor R
BE
(R
BP
, R
BL
, R
BN
in the Functional
Block Diagram), which increase the pole frequency to:
f
p
=f
T
*(1+ Hfe *re/R
BE
)/Hfe, where re=KT/qIc. So choose the
lowest value R
BE
in the design as long as there is still
enough base current (I
B
) to support the maximum output
current (I
C
).
We will take as an example the V
LOGIC
linear regulator. If a
Fairchild FMMT549 PNP transistor is used as the external
pass transistor, Q5 in the application diagram, then for a
maximum V
LOGIC
operating requirement of 500mA the data
sheet indicates Hfe_min = 100.
The base-emitter saturation voltage is: Vbe_max = 1.25V
(note this is normally a Vbe ~ 0.7V, however, for the Q5
transistor an internal Darlington arrangement is used to
increase it's current gain, giving a 'base-emitter' voltage of
2 x V
BE
).
(Note that using a high current Darlington PNP transistor for
Q5 requires that V
IN
> V
LOGIC
+ 2V. Should a lower input
voltage be required, then an ordinary high gain PNP
transistor should be selected for Q5 so as to allow a lower
collector-emitter saturation voltage).
For the EL7585, the minimum drive current is:
I_DRVL_min = 8mA
The minimum base-emitter resistor, R
BL
, can now be
calculated as:
R
BL
_min = V
BE
_max/(I_DRVL_min - Ic/Hfe_min) =
1.25V/(8mA - 500mA/100) = 417
This is the minimum value that can be used - so, we now
choose a convenient value greater than this minimum value;
say 500
. Larger values may be used to reduce quiescent
current, however, regulation may be adversely affected, by
supply noise if R
BL
is made too high in value.
EL7585
FB
LX
V
BOOST
V
IN
FIGURE 22. CASCADED MOSFET TOPOLOGY FOR HIGH
OUTPUT VOLTAGE APPLICATIONS
-
GMP
+
-
+
36V
ESD
CLAMP
LDO_ON
PG_LDOP
1: Np
FBP
DRVP
7k
R
BP
V
BOOST
0.1μF
0.1μF
CP (TO 36V)
20k
R
P2
R
P1
C
ON
V
ON
(TO 35V)
LX
0.9V
Q3
FIGURE 23. V
ON
FUNCTIONAL BLOCK DIAGRAM
EL7585
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| EL7585ILZ-T13 | 功能描述:IC POWER SUPPLY TFT-LCD 20-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,000 系列:- 應(yīng)用:電源，ICERA E400，E450 輸入電壓:4.1 V ~ 5.5 V 輸出數(shù):10 輸出電壓:可編程 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:42-WFBGA，WLCSP 供應(yīng)商設(shè)備封裝:42-WLP 包裝:帶卷 (TR) |
| EL7585ILZ-T7 | 功能描述:IC POWER SUPPLY TFT-LCD 20-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,000 系列:- 應(yīng)用:電源，ICERA E400，E450 輸入電壓:4.1 V ~ 5.5 V 輸出數(shù):10 輸出電壓:可編程 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:42-WFBGA，WLCSP 供應(yīng)商設(shè)備封裝:42-WLP 包裝:帶卷 (TR) |
| EL7586 | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:TFT-LCD Power Supply |
| EL7586_06 | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:TFT-LCD Power Supply |
| EL7586A | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:TFT-LCD Power Supply |
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