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參數(shù)資料
| 型號(hào)： | LM3102MH |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SIMPLE SWITCHER㈢ Synchronous 1MHz 2.5A Step-Down Voltage Regulator |
| 中文描述： | SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | PLASTIC, TSSOP-20 |
| 文件頁數(shù)： | 13/18頁 |
| 文件大?。?/td> | 330K |
| 代理商： | LM3102MH |
Applications Information
EXTERNAL COMPONENTS
The following guidelines can be used to select external com-
ponents.
R
FB1
and R
FB2
: These resistors should be chosen from stan-
dard values in the range of 1.0 k
to 10 k
, satisfying the
following ratio:
R
FB1
/R
FB2
= (V
OUT
/0.8V) - 1
For V
= 0.8V, the FB pin can be connected to the output
directly with a pre-load resistor drawing more than 20 μA. It is
because the converter operation needs a minimum inductor
current ripple to maintain good regulation when no load is
connected.
R
:
Equation (2) can be used to select R
if a desired op-
erating frequency is selected. But the minimum value of
R
is determined by the minimum on-time. It can be calcu-
lated as follows:
(7)
(8)
If R
calculated from (2) is smaller than the minimum value
determined in (8), a lower frequency should be selected to re-
calculate R
by (2). Alternatively, V
can also be limited
in order to keep the frequency unchanged. The relationship
of V
IN(MAX)
and R
ON
is shown in
Figure 5
.
On the other hand, the minimum off-time of 260 ns can limit
the maximum duty ratio. Larger R
should be selected in any
application requiring large duty ratio.
30021329
FIGURE 5. Maximum V
IN
for selected R
ON
L:
The main parameter affected by the inductor is the ampli-
tude of inductor current ripple (I
LR
). Once I
LR
is selected, L can
be determined by:
(9)
where V
IN
is the maximum input voltage and f
SW
is determined
from (2).
If the output current I
is determined, by assuming that
I
OUT
= I
L
, the higher and lower peak of I
LR
can be determined.
Beware that the higher peak of I
should not be larger than
the saturation current of the inductor and current limits of the
main and synchronous MOSFETs. Also, the lower peak of
I
LR
must be positive if CCM operation is required.
30021331
FIGURE 6. Inductor selection for V
OUT
= 3.3V
30021332
FIGURE 7. Inductor selection for V
OUT
= 0.8V
Figure 6
and
Figure 7
show curves on inductor selection for
various V
OUT
and R
ON
. For small R
ON
, according to (8), V
IN
is
limited. Some curves are therefore limited as shown in the
figures.
C
:
The capacitor on the V
output provides not only noise
filtering and stability, but also prevents false triggering of the
V
UVLO at the main MOSFET on/off transitions. C
should be no smaller than 680 nF for stability, and should be
a good quality, low ESR, ceramic capacitor.
C
OUT
and C
OUT3
:
C
OUT
should generally be no smaller than
10 μF. Experimentation is usually necessary to determine the
minimum value for C
, as the nature of the load may require
a larger value. A load which creates significant transients re-
quires a larger C
OUT
than a fixed load.
C
is a small value ceramic capacitor located close to the
LM3102 to further suppress high frequency noise at V
OUT
. A
100 nF capacitor is recommended.
13
www.national.com
L
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3102MH/NOPB | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 SYNC 1MHZ 2.5A STEP- DOWN VLTG REG RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| LM3102MHX | 制造商:Texas Instruments 功能描述:Conv DC-DC Single Step Down 4.5V to 42V 20-Pin TSSOP EP T/R |
| LM3102MHX/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM3102QMH/NOPB | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 SIMPLE SWITCHER Sync 1MHz 2.5A SD Vtg Reg RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| LM3102QMHX/NOPB | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 SIMPLE SWITCHER Sync 1MHz 2.5A SD Vtg Reg RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
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