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參數資料
| 型號： | ADP3166 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 5-Bit Programmable 2-, 3-, 4-Phase Synchronous Buck Controller |
| 中文描述： | 5位可編程2 - ，3 - ，4相同步降壓控制器 |
| 文件頁數： | 11/20頁 |
| 文件大小： | 351K |
| 代理商： | ADP3166 |
REV. 0
ADP3166
–11–
Soft Start and Current Limit Latch-Off Delay Times
Because the soft start and current limit latch-off delay functions
share the DELAY pin, these two parameters must be considered
together. The first step is to set
C
DLY
for the soft start ramp.
This ramp is generated with a 20
μ
A internal current source.
The value of
R
DLY
will have a second order impact on the soft-
start time because it sinks part of the current source to ground.
However, as long as
R
DLY
is kept greater than 200 k
, this effect
is minor. The value for
C
DLY
can be approximated using
C
=
A –
μ
V
×
R
t
V
DLY
VID
DLY
SS
VID
20
2
×
(2)
where
t
SS
is the desired soft start time. Assuming an
R
DLY
of 390
k
and a desired a soft start time of 3 ms,
C
DLY
is 36 nF.
The closest standard value for C
CS
is 39 nF. Once
C
DLY
has
been chosen,
R
DLY
can be calculated for the current limit latch
off time using
R
=
t
C
DLY
DLY
DLY
1.
×
(3)
If the result for
R
DLY
is less than 200 k
, then a smaller soft start
time should be considered by recalculating the equation for
C
DLY
or a longer latch-off time should be used. In no case should
R
DLY
be less than 200 k
. In this example, a delay time of 8 ms makes
R
DLY
= 402 k
. The closest standard 5% value is 390 k
.
Inductor Selection
The choice of inductance for the inductor determines the ripple
current in the inductor. Less inductance leads to more ripple
current, which increases the output ripple voltage and conduc-
tion losses in the MOSFETs but allows using smaller-size
inductors and, for a specified peak-to-peak transient deviation,
less total output capacitance. Conversely, a higher inductance
means lower ripple current and reduced conduction losses, but
requires larger-size inductors and more output capacitance for
the same peak-to-peak transient deviation. In any multiphase
converter, a practical value for the peak-to-peak inductor ripple
current is less than 50% of the maximum dc current in the same
inductor. Equation 4 shows the relationship between the induc-
tance, oscillator frequency, and peak-to-peak ripple current in
the inductor. Equation 5 can be used to determine the mini-
mum inductance based on a given output ripple voltage:
×
(
×
L
×
f
V
SW
RIPPLE
Solving Equation 5 for a 10 mV p-p output ripple voltage yields
I =V
– D
f
VID
SW
×
)
1
(4)
L
≥
×
×
)
(
)
V
R
– n
D
VID
OD
1
(5)
L
≥
×
×
(
×
)
1. V
1. m
kHz
1 0 375
10
mV
330
540
– .
=
nH
If the ripple voltage is less than that designed for, the inductor can
be made smaller until the ripple value is met. This will allow opti-
mal transient response and minimum output decoupling.
The smallest possible inductor should be used to minimize the
number of output capacitors. A 600 nH inductor is a good
choice for a starting point, and it gives a calculated ripple cur-
rent of 6.6 A. The inductor should not saturate at the peak
current of 22 A, and should be able to handle the sum of the
power dissipation caused by the average current of 18.7 A in the
winding and the core loss.
Another important factor in the inductor design is the DCR,
which is used for measuring the phase currents. A large DCR
will cause excessive power losses, while too small a value will
lead to increased measurement error. A good rule is to have the
DCR be about 1 to 1 1/2 times the static droop resistance (R
O
).
For our example, we are using an inductor with a DCR of 1.6 m
.
Designing an Inductor
Once the inductance and DCR are known, the next step is either
to design an inductor or to find a standard inductor that comes as
close as possible to meeting the overall design goals. It is also
important to have the inductance and DCR tolerance specified to
keep the accuracy of the system controlled. Using 20% for the
inductance and 8% for the DCR (at room temperature) are rea-
sonable tolerances that most manufacturers can meet.
The first decision in designing the inductor is to choose the core
material. There are several possibilities for providing low core
loss at high frequencies. Two examples are the powder cores
(e.g., Kool-M
μ
from Magnetics, Inc. or Micrometals) and the
gapped soft ferrite cores (e.g., 3F3 or 3F4 from Philips). Low
frequency powdered iron cores should be avoided due to their
high core loss, especially when the inductor value is relatively
low and the ripple current is high.
The best choices for a core geometry are closed-loop types, such
as pot cores, PQ, U, and E cores, or toroids. A good compromise
between price and performance are cores with a toroidal shape.
There are many useful references for quickly designing a power
inductor, such as
Magnetic Designer Software
Intusoft (http://www.intusoft.com)
Designing Magnetic Components for High-Frequency
DC-DC Converters
McLyman, Kg Magnetics
ISBN 1-883107-00-8
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相關代理商/技術參數 |
參數描述 |
|---|---|
| ADP3166JRU-REEL | 功能描述:IC REG BUCK 5BIT 2-4PHAS 28TSSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩壓器 - 專用型 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,000 系列:- 應用:電源，ICERA E400，E450 輸入電壓:4.1 V ~ 5.5 V 輸出數: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 供應商設備封裝:42-WLP 包裝:帶卷 (TR) |
| ADP3166JRU-REEL7 | 功能描述:IC REG BUCK 5BIT 2-4PHAS 28TSSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩壓器 - 專用型 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,000 系列:- 應用:電源，ICERA E400，E450 輸入電壓:4.1 V ~ 5.5 V 輸出數: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 供應商設備封裝:42-WLP 包裝:帶卷 (TR) |
| ADP3166JRUZ-REEL | 功能描述:IC REG BUCK 5BIT 2-4PHAS 28TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩壓器 - 專用型 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,000 系列:- 應用:電源，ICERA E400，E450 輸入電壓:4.1 V ~ 5.5 V 輸出數: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 供應商設備封裝:42-WLP 包裝:帶卷 (TR) |
| ADP3167 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:ADP3160/ADP3167: 5-Bit Programmable 2-Phase Synchronous Buck Controller Data Sheet (Rev. B. 5/02) |
| ADP3167JR | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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