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參數(shù)資料
| 型號： | LTC3411 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | 1.25A, 4MHz, Synchronous Step-Down DC/DC Converter |
| 中文描述： | 電流1.25A，4MHz，同步降壓型DC / DC轉(zhuǎn)換器 |
| 文件頁數(shù)： | 8/20頁 |
| 文件大?。?/td> | 288K |
| 代理商： | LTC3411 |
LTC3411
8
sn3411 3411fs
APPLICATIU
A general LTC3411 application circuit is shown in
Figure5. External component selection is driven by the
load requirement, and begins with the selection of the
inductor L1. Once L1 is chosen, C
IN
and C
OUT
can be
selected.
W
U
U
Operating Frequency
Selection of the operating frequency is a tradeoff between
efficiency and component size. High frequency operation
allows the use of smaller inductor and capacitor values.
Operation at lower frequencies improves efficiency by
reducing internal gate charge losses but requires larger
inductance values and/or capacitance to maintain low
output ripple voltage.
The operating frequency, f
O
, of the LTC3411 is determined
by an external resistor that is connected between the R
T
pin and ground. The value of the resistor sets the ramp
current that is used to charge and discharge an internal
timing capacitor within the oscillator and can be calculated
by using the following equation:
R
f
T
O
=
( )
( )
9 78 10
11
.
1 08
.
or can be selected using Figure 2.
The maximum usable operating frequency is limited by the
minimum on-time and the duty cycle. This can be calcu-
lated as:
f
O(MAX)
≈
6.67 (V
OUT
/ V
IN(MAX)
) (MHz)
The minimum frequency is limited by leakage and noise
coupling due to the large resistance of R
T
.
Inductor Selection
Although the inductor does not influence the operating
frequency, the inductor value has a direct effect on ripple
current. The inductor ripple current
I
L
decreases with
higher inductance and increases with higher V
IN
or V
OUT
:
=
I
V
f
L
V
V
L
OUT
O
OUT
IN
1
Accepting larger values of
I
L
allows the use of low
inductances, but results in higher output voltage ripple,
greater core losses, and lower output current capability.
A reasonable starting point for setting ripple current is
I
L
=0.3 I
LIM
, where I
LIM
is the peak switch current limit.
The largest ripple current
I
L
occurs at the maximum
input voltage. To guarantee that the ripple current stays
below a specified maximum, the inductor value should be
chosen according to the following equation:
L
V
f
I
V
V
OUT
O
L
OUT
IN MAX
(
=
)
1
The inductor value will also have an effect on Burst Mode
operation. The transition from low current operation begins
when the peak inductor current falls below a level set by the
burst clamp. Lower inductor values result in higher ripple
current which causes this to occur at lower load currents.
This causes a dip in efficiency in the upper range of low
current operation. In Burst Mode operation, lower induc-
tance values will cause the burst frequency to increase.
R
T
(k
)
0
0
F
0.5
1.5
2.0
2.5
1000
4.5
T
A
= 25
°
C
3411 F02
1.0
500
1500
3.0
3.5
4.0
Figure 2. Frequency vs R
T
Inductor Core Selection
Different core materials and shapes will change the size/
current and price/current relationship of an inductor. Tor-
oid or shielded pot cores in ferrite or permalloy materials
are small and don’t radiate much energy, but generally cost
more than powdered iron core inductors with similar
electrical characteristics. The choice of which style induc-
tor to use often depends more on the price vs size require-
ments and any radiated field/EMI requirements than on
what the LTC3411 requires to operate. Table 1 shows some
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3411A | 制造商:LINER 制造商全稱:Linear Technology 功能描述:1.25A, 4MHz, Synchronous Step-Down DC/DC Converter |
| LTC3411AEDD#PBF | 功能描述:IC REG BUCK SYNC ADJ 1.25A 10DFN 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:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC3411AEDD#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 1.25A 10DFN 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:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC3411AEDD-PBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:1.25A, 4MHz, Synchronous Step-Down DC/DC Converter |
| LTC3411AEDD-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:1.25A, 4MHz, Synchronous Step-Down DC/DC Converter |
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