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參數(shù)資料
| 型號： | LTC1475 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Low Quiescent Current High Efficiency Step-Down Converters(低靜態(tài)電流，高效率步降轉(zhuǎn)換器) |
| 中文描述： | 低靜態(tài)電流高效率降壓轉(zhuǎn)換器（低靜態(tài)電流，高效率步降轉(zhuǎn)換器） |
| 文件頁數(shù)： | 13/20頁 |
| 文件大?。?/td> | 296K |
| 代理商： | LTC1475 |
13
LTC1474/LTC1475
APPLICATIO
S I
FOR
ATIO
U
W
U
U
Figure 9. LTC1474/LTC1475 Layout Diagram (See Board Layout Checklist)
+
+
V
OUT
V
IN
V
IN
R
SENSE
V
FB
C
OUT
C
IN
10pF
1000pF
R2
100k
LTC1474
R1
D1
LBO
LBI
GND
RUN
SENSE
SW
L
1474/75 F09
8
7
6
5
1
2
3
4
BOLD LINES INDICATE HIGH PATH CURRENTS
0.1
μ
F
OUTPUT DIVIDER REQUIRED WITH
ADJUSTABLE VERSION ONLY
5. Are the signal and power grounds segregated The
signal ground consists of the (–) plate of C
OUT
, Pin 4 of
the LTC1474/LTC1475 and the resistive divider. The
power ground consists of the Schottky diode anode,
the (–) plate of C
IN
and the 0.1
μ
F decoupling capacitor.
6. Is a 100k resistor connected in series between RUN
(Pin 8) and the RUN control voltage The resistor
should be as close as possible to Pin 8.
Design Example (Refer to R
SENSE
and Inductor
Selection)
As a design example, assume V
IN
= 10V, V
OUT
= 3V, and
a maximum average output current I
MAX
= 100mA. With
this information, we can easily calculate all the important
components:
From the equation (1),
R
SENSE
= (0.067/0.1) – 0.25 = 0.42
Using the standard resistors (1
, 1
and 2
) in parallel
provides 0.4
without having to use a more expensive
low value current shunt type resistor (see R
SENSE
Selec-
tion section).
With R
SENSE
= 0.4
, the peak inductor current I
PEAK
is
calculated from (2), neglecting the second term, to be
150mA. The minimum inductance is, therefore, from the
equation (3) and assuming V
D
= 0.4V,
(
0 15 0 1
L
s
H
MIN
=
+
)(
)
=
0 75 3 3 0 4 4 75
.
.
264
.
.
μ
μ
From Figure 3, an inductance of 270
μ
H is chosen from the
recommended region. The CDRH73-271 or CD54-271 is a
good choice for space limited applications.
For the feedback resistors, choose R1 = 1M to minimize
supply current. R2 can then be calculated from the equa-
tion (4) to be:
R
V
1 23
.
R
M
OUT
2
1
1 1 43
=
.
For the catch diode, the MBR0530 will work well in this
application.
For the input and output capacitors, AVX 4.7
μ
F and 100
μ
F,
respectively, low ESR TPS series work well and meet the
RMS current requirement of 100mA/2 = 50mA. They are
available in small “C” case sizes with 0.15
ESR. The
0.15
output capacitor ESR will result in 25mV of output
voltage ripple.
Figure 10 shows the complete circuit for this example.
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| LTC1475CMS8 | 功能描述:IC REG BUCK ADJ 0.75A 8MSOP RoHS:否 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:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LTC1475CMS8#PBF | 功能描述:IC REG BUCK ADJ 0.75A 8MSOP 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:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LTC1475CMS8#TR | 功能描述:IC REG BUCK ADJ 0.75A 8MSOP RoHS:否 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:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LTC1475CMS8#TRPBF | 功能描述:IC REG BUCK ADJ 0.75A 8MSOP 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:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
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