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參數(shù)資料
| 型號(hào)： | LT3470ETS8 |
| 廠商： | Linear Integrated Systems |
| 英文描述： | Micropower Buck Regulator with Integrated Boost and Catch Diodes |
| 中文描述： | 微功耗降壓穩(wěn)壓器與集成升壓二極管和捕捉 |
| 文件頁(yè)數(shù)： | 9/16頁(yè) |
| 文件大?。?/td> | 205K |
| 代理商： | LT3470ETS8 |
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9
LT3470
3470f
current is reduced at high temperatures—see inductor
vendors for more information.
Input Capacitor
Step-down regulators draw current from the input supply
in pulses with very fast rise and fall times. The input
capacitor is required to reduce the resulting voltage ripple
at the V
IN
pin of the LT3470 and to force this switching
current into a tight local loop, minimizing EMI. The input
capacitor must have low impedance at the switching
frequency to do this effectively. A 1
μ
F to 2.2
μ
F ceramic
capacitor satisfies these requirements.
If the input source impedance is high, a larger value
capacitor may be required to keep input ripple low. In this
case, an electrolytic of 10
μ
F or more in parallel with a 1
μ
F
ceramic is a good combination. Be aware that the input
capacitor is subject to large surge currents if the LT3470
circuit is connected to a low impedance supply, and that
some electrolytic capacitors (in particular tantalum) must
be specified for such use.
Output Capacitor and Output Ripple
The output capacitor filters the inductor’s ripple current
and stores energy to satisfy the load current when the
LT3470 is quiescent. In order to keep output voltage ripple
low, the impedance of the capacitor must be low at the
LT3470’s switching frequency. The capacitor’s equivalent
series resistance (ESR) determines this impedance. Choose
one with low ESR intended for use in switching regulators.
The contribution to ripple voltage due to the ESR is
approximately I
LIM
ESR. ESR should be less than ~150m
.
The value of the output capacitor must be large enough to
accept the energy stored in the inductor without a large
change in output voltage. Setting this voltage step equal to
1% of the output voltage, the output capacitor must be:
C
L
I
V
OUT
LIM
OUT
>
50
2
Where I
LIM
is the top current limit with V
FB
= 0V (see
Electrical Characteristics). For example, an LT3470 pro-
ducing 3.3V with L = 33
μ
H requires 22
μ
F. The calculated
value can be relaxed if small circuit size is more important
than low output ripple.
Sanyo’s POSCAP series in B-case and provides very good
performance in a small package for the LT3470. Similar
performance in traditional tantalum capacitors requires a
larger package (C-case). With a high quality capacitor
filtering the ripple current from the inductor, the output
voltage ripple is determined by the delay in the LT3470’s
feedback comparator. This ripple can be reduced further
by adding a small (typically 22pF) phase lead capacitor
between the output and the feedback pin.
APPLICATIU
W
U
U
Table 2. Inductor Vendors
VENDOR
Coilcraft
URL
www.coilcraft.com
PART SERIES
DO1605
ME3220
DO3314
CR32
CDRH3D16/HP
CDRH3D28
CDRH2D18/HP
DB320C
D52LC
WE-PD2 Typ S
WE-TPC Typ S
SD10
LQH43C
LQH32C
INDUCTANCE RANGE (
μ
H)
10 to 47
10 to 47
10 to 47
10 to 47
10 to 33
10 to 47
10 to 15
10 to 27
10 to 47
10 to 47
10 to 22
10 to 47
10 to 47
10 to 15
SIZE (mm)
1.8
×
5.4
×
4.2
2.0
×
3.2
×
2.5
1.4
×
3.3
×
3.3
3.0
×
3.8
×
4.1
1.8
×
4.0
×
4.0
3.0
×
4.0
×
4.0
2.0
×
3.2
×
3.2
2.0
×
3.8
×
3.8
2.0
×
5.0
×
5.0
3.2
×
4.0
×
4.5
1.6
×
3.8
×
3.8
1.0
×
5.0
×
5.0
2.6
×
3.2
×
4.5
1.6
×
2.5
×
3.2
Sumida
www.sumida.com
Toko
www.tokoam.com
Würth Elektronik
www.we-online.com
Coiltronics
Murata
www.cooperet.com
www.murata.com
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT3470ETS8#PBF | 制造商:Linear Technology 功能描述:DC-DC CONVERTER BUCK ADJ 20 制造商:Linear Technology 功能描述:DC-DC CONVERTER, BUCK, ADJ, 200mA, TSOT-23-8; Primary Input Voltage:40V; No. of Outputs:1; Output Current:200mA; No. of Pins:8; Operating Temperature Min:-40C; Operating Temperature Max:85C; Package / Case:8-TSOT-23 ;RoHS Compliant: Yes |
| LT3470ETS8#TR | 制造商:Linear Technology 功能描述:Conv DC-DC Single Step Down 4V to 40V 8-Pin TSOT-23 T/R |
| LT3470ETS8#TRM | 制造商:Linear Technology 功能描述:Conv DC-DC Single Step Down 4V to 40V 8-Pin TSOT-23 T/R |
| LT3470ETS8#TRMPBF | 功能描述:IC REG BUCK ADJ 0.2A TSOT23-8 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)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(kāi)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(yè)面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2 |
| LT3470ETS8#TRMPBF | 制造商:Linear Technology 功能描述:DC/DC Converter IC 制造商:Linear Technology 功能描述:IC, BUCK REGULATOR, 8-TSOT-23 |
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