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參數(shù)資料
| 型號(hào)： | LT1956-5IGN |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3 A SWITCHING REGULATOR, 570 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.150 INCH, PLASTIC, SSOP-16 |
| 文件頁數(shù)： | 2/24頁 |
| 文件大?。?/td> | 437K |
| 代理商： | LT1956-5IGN |
10
LT1956/LT1956-5
APPLICATIO S I FOR ATIO
WU
UU
V
I
ESR
ESL
dI
dt
RIPPLE
LP P
=
()( )+()
-
Σ
where:
ESR = equivalent series resistance of the output
capacitor
ESL = equivalent series inductance of the output
capacitor
dI/dt = slew rate of inductor ripple current = VIN/L
Peak-to-peak ripple current (ILP-P) through the inductor
and into the output capacitor is typically chosen to be
between 20% and 40% of the maximum load current. It is
approximated by:
I
VV
V
Vf L
LP P
OUT
IN
OUT
IN
- =
()(
)
()( )( )
–
Example: with VIN = 12V, VOUT = 5V, L = 18H, ESR = 0.1
and ESL = 10nH, output ripple voltage can be approxi-
mated as follows:
IA
dI
dt
V
L
V
IN
RIPPLE
LP-P
P-P
=
()
()
()(
)
=
==
=
()( )+
()(
)
=+
=
512 5
12 500 10
18 10
0 324
12
18 10
067 10
0 324 0 1
10 10
0 67 10
0 0324 0 0067
0 039
36
6
96
.
.
..
.
..
.
–
Σ
To reduce output ripple voltage further requires an in-
crease in the inductor value or a reduction in the capacitor
ESR. The latter can effect loop stability since the ESR
forms a useful zero in the overall loop response. Typically
the inductor value is adjusted with the trade-off being a
physically larger inductor with the possibility of increased
component height and cost. Choosing a smaller inductor
with lighter loads may result in discontinuous operation
but the LT1956 is designed to work well in both continu-
ous or discontinuous mode.
Peak Inductor Current and Fault Current
To ensure that the inductor will not saturate, the peak
inductor current should be calculated knowing the maxi-
mum load current. An appropriate inductor should then
be chosen. In addition, a decision should be made whether
or not the inductor must withstand continuous fault
conditions.
If maximum load current is 0.5A, for instance, a 0.5A
inductor may not survive a continuous 2A overload condi-
tion. Dead shorts will actually be more gentle on the
inductor because the LT1956 has frequency and current
limit foldback.
Peak current can be significantly higher than output cur-
rent, especially with smaller inductors and lighter loads,
so don’t omit this step. Powdered iron cores are forgiving
because they saturate softly, whereas ferrite cores satu-
rate abruptly. Other core materials fall somewhere in
between. The following formula assumes continuous mode
of operation, but errs only slightly on the high side for
discontinuous mode, so it can be used for all conditions.
I
II
I
VV
V
Vf L
PEAK
OUT
LP P
OUT
IN
OUT
IN
=
+
=
()(
)
()( )( )()
()
–
-
22
Table 2
VENDOR/
VALUE
IDC(MAX)
DCR
HEIGHT
PART NO.
(
H)
(Amps)
(Ohms)
(mm)
Coiltronics
TP3-4R7
4.7
1.5
0.181
2.2
CTX5-1P
5
2.0
0.041
4.2
TP4-100
10
1.5
0.146
3.0
CTX10-1P
10
1.7
0.057
4.2
CTX15-1P
15
1.4
0.087
4.2
CTX20-2P
20
1.5
0.097
4.2
Sumida
CDRH4D28-4R7
4.7
1.32
0.072
3.0
CDRH5D28-100
10
1.30
0.065
3.0
CDRH6D28-150
15
1.40
0.084
3.0
CDRH6D28-180
18
1.32
0.095
3.0
CDRH6D38-220
22
1.30
0.096
4.0
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| LT1956EFE#PBF | 功能描述:IC REG BUCK ADJ 1.5A 16TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開關(guān):2MHz 電流 - 輸出:500mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:6-UFDFN 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2 |
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