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參數(shù)資料
| 型號： | LTC3642IMS8E-3.3E#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.13 A SWITCHING REGULATOR, PDSO8 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-8 |
| 文件頁數(shù)： | 4/20頁 |
| 文件大?。?/td> | 306K |
| 代理商： | LTC3642IMS8E-3.3E#PBF |
LTC3642
12
3642fa
APPLICATIONS INFORMATION
This formula has a maximum at VIN = 2VOUT, where
IRMS = IOUT/2. This simple worst-case condition is
commonly used for design because even signicant
deviations do not offer much relief. Note that ripple current
ratings from capacitor manufacturers are often based
only on 2000 hours of life which makes it advisable to
further derate the capacitor, or choose a capacitor rated
at a higher temperature than required. Several capacitors
may also be paralleled to meet size or height requirements
in the design.
The output capacitor, COUT, lters the inductor’s ripple
current and stores energy to satisfy the load current
when the LTC3642 is in sleep. The output voltage ripple
during a burst cycle is dominated by the output capacitor
equivalent series resistance (ESR) and can be estimated
by the following equation:
V
VI
ESR
OUT
PEAK
160
<
≤
Δ
where the lower limit of VOUT/160 is due to the 5mV
feedback comparator hysteresis.
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:
CL
I
V
OUT
PEAK
OUT
>
50
2
Typically, a capacitor that satises the ESR requirement is
adequate to lter the inductor ripple. To avoid overheating,
the output capacitor must also be sized to handle the ripple
current generated by the inductor. The worst-case ripple
current in the output capacitor is given by IRMS = IPEAK/2.
Multiple capacitors placed in parallel may be needed to
meet the ESR and RMS current handling requirements.
Dry tantalum, special polymer, aluminum electrolytic,
and ceramic capacitors are all available in surface mount
packages. Special polymer capacitors offer very low ESR
but have lower capacitance density than other types.
Tantalum capacitors have the highest capacitance density
but it is important only to use types that have been surge
tested for use in switching power supplies. Aluminum
electrolytic capacitors have signicantly higher ESR but
can be used in cost-sensitive applications provided that
consideration is given to ripple current ratings and long-
term reliability. Ceramic capacitors have excellent low ESR
characteristics but can have high voltage coefcient and
audible piezoelectric effects. The high quality factor (Q)
of ceramic capacitors in series with trace inductance can
also lead to signicant ringing.
Using Ceramic Input and Output Capacitors
Higher value, lower cost ceramic capacitors are now
becoming available in smaller case sizes. Their high ripple
current, high voltage rating and low ESR make them ideal
for switching regulator applications. However, care must
be taken when these capacitors are used at the input and
output. When a ceramic capacitor is used at the input and
the power is supplied by a wall adapter through long wires,
a load step at the output can induce ringing at the input,
VIN. At best, this ringing can couple to the output and be
mistaken as loop instability. At worst, a sudden inrush
of current through the long wires can potentially cause a
voltage spike at VIN large enough to damage the part.
For applications with inductive source impedance, such
as a long wire, a series RC network may be required in
parallel with CIN to dampen the ringing of the input supply.
Figure 5 shows this circuit and the typical values required
to dampen the ringing.
LTC3642
VIN
CIN
LIN
3642 F05
4 CIN
R =
LIN
CIN
Figure 5. Series RC to Reduce VIN Ringing
Output Voltage Programming
For the adjustable version, the output voltage is set by
an external resistive divider according to the following
equation:
VV
R
OUT =+
08
1
2
.
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| LTC3642IMS8E-5#PBF | 功能描述:IC REG BUCK SYNC 5V 50MA 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:- 標準包裝: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) 供應商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LTC3642IMS8E-5#TRPBF | 功能描述:IC REG BUCK SYNC 5V 50MA 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:- 標準包裝: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) 供應商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LTC3642IMS8EPBF | 制造商:Linear Technology 功能描述:DC-DC Converter Step-Down 4.5-45V MSOP8 |
| LTC3646EDE#PBF | 制造商:Linear Technology 功能描述: 制造商:Linear Technology 功能描述:IC REG BUCK SYNC ADJ 1A 14DFN 制造商:Linear Technology 功能描述:BUCK 4-40V 3MHZ 1A 2-30V 14DFN 制造商:Linear Technology 功能描述:BUCK, 4-40V, 3MHZ, 1A, 2-30V, 14DFN 制造商:Linear Technology 功能描述:DP-SWREG/Monolithic, 40V, 1A, 100uA IQ Synchronous Step-Down Converter 制造商:Linear Technology 功能描述:DC-DC CONVERTER, BUCK, ADJ, 3MHZ, DFN-14, Primary Input Voltage:40V, No. of Outputs:1, Output Current:1A, No. of Pins:14, Operating Temperature Min:-40C, Operating Temperature Max:85C, MSL:MSL 1 - Unlimited, Package / Case:14-DFN , RoHS Compliant: Yes |
| LTC3646EDE#TRPBF | 制造商:Linear Technology 功能描述:IC REG BUCK SYNC ADJ 1A 14DFN 制造商:Linear Technology 功能描述:DP-SWREG/Monolithic, 40V, 1A, 100uA IQ Synchronous Step-Down Converter 制造商:Linear Technology 功能描述:DC-DC CONVERTER, BUCK, ADJ, 3MHZ, DFN-14, Primary Input Voltage:40V, No. of Outputs:1, Output Current:1A, No. of Pins:14, Operating Temperature Min:-40C, Operating Temperature Max:85C, MSL:MSL 1 - Unlimited, Package / Case:14-DFN , RoHS Compliant: Yes |
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