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參數(shù)資料
| 型號： | LTC1626 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Low Voltage, High Efficiency Step-Down DC/DC Converter(低壓，高效率，步降DC/DC變換器) |
| 中文描述： | 低，高效率步電壓型DC / DC轉(zhuǎn)換器（低壓，高效率，步降直流/直流變換器） |
| 文件頁數(shù)： | 7/12頁 |
| 文件大?。?/td> | 242K |
| 代理商： | LTC1626 |
7
LTC1626
sequence, the LTC1626 will delay entering Burst Mode
operation and efficiency will be degraded at low currents.
APPLICATIO
S I
FOR
ATIO
U
W
U
U
the P-channel switch duty cycle. At high input voltages,
the diode conducts most of the time. As V
IN
approaches
V
OUT
, the diode conducts only a small fraction of the time.
The most stressful condition for the diode is when the
regulator output is shorted to ground.
Under short-circuit conditions, the diode must safely
handle I
SC(PK)
at close to 100% duty cycle. Most LTC1626
circuits will be well served by either an MBRM5819 or an
MBRS130LT3. An MBR0520LT1 is a good choice for
I
OUT(MAX)
≤
500mA.
Input Capacitor (C
IN
) Selection
In continuous mode, the input current of the converter is
a square wave of duty cycle V
OUT
/V
IN
. To prevent large
voltage transients, a low effective series resistance (ESR)
input capacitor must be used. In addition, the capacitor
must handle a high RMS current. The C
IN
RMS current is
given by:
(
I
I
V
V
V
V
A
RMS
OUT
OUT
IN
OUT
IN
≈
)
[
]
( )
1 2
/
This formula has a maximum at V
IN
= 2V
OUT
, where
I
RMS
= I
OUT
/2. This simple worst case is commonly used
to design because even significant deviations do not offer
much relief. Note that capacitor manufacturer’s ripple
current ratings are often based on only 2000 hours life-
time. This make it advisable to further derate the capacitor,
or choose a capacitor rated at a higher temperature than
required. Do not underspecify this component An addi-
tional 0.1
μ
F ceramic capacitor is also required on PWR V
IN
for high frequency decoupling.
Output Capacitor (C
OUT
) Selection
The selection of C
OUT
is driven by the ESR for proper
operation of the LTC1626. The required ESR of C
OUT
is:
ESR
COUT
< 50mV/I
RIPPLE
where I
RIPPLE
is the ripple current of the inductor. For the
case where the I
RIPPLE
is 25mV/R
SENSE
, the required ESR
of C
OUT
is:
Kool M
μ
is a registered trademark of Magnetics, Inc.
INPUT VOLTAGE (V)
200
180
160
140
120
100
80
60
40
20
0
F
1626 F03
5.0 5.5 6.0 6.5 7.0 7.5
4.5
2.5
3.5 4.0
3.0
FIGURE 1 CIRCUIT
Inductor Core Selection
With the value of L selected, the type of inductor must be
chosen. Basically, there are two kinds of losses in an
inductor—core and copper losses.
Core losses are dependent on the peak-to-peak ripple
current and core material. However, they are independent
of the physical size of the core. By increasing inductance,
the peak-to-peak inductor ripple current will decrease,
therefore reducing core loss. Utilizing low core loss mate-
rial, such as molypermalloy or Kool M
μ
will allow the user
to concentrate on reducing copper loss and preventing
saturation.
Although higher inductance reduces core loss, it increases
copper loss as it requires more windings. When space is
not a premium, larger wire can be used to reduce the wire
resistance. This also prevents excessive heat dissipation
in the inductor.
Catch Diode Selection
Losses in the catch diode depend on forward drop and
switching times. Therefore, Schottky diodes are a good
choice for low drop and fast switching times.
The catch diode carries the load current during the off-
time. The average diode current is therefore dependent on
Figure 3. Operating Frequency vs Supply Voltage
for Circuit Shown in Figure 1
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1626CS | 制造商:Linear Technology 功能描述:Low Volt Hi Eff Stepdn DC/DC Conv. |
| LTC1627CS8 | 功能描述:IC REG BUCK SYNC ADJ 0.5A 8SOIC 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:- 標準包裝: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 |
| LTC1627CS8#PBF | 功能描述:IC REG BUCK SYNC ADJ 0.5A 8SOIC 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:- 標準包裝: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 |
| LTC1627CS8#TR | 功能描述:IC REG BUCK SYNC ADJ 0.5A 8SOIC 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:- 標準包裝: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 |
| LTC1627CS8#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 0.5A 8SOIC 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:- 標準包裝: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 |
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