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| 型号： | LTC3852EUDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 24/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR DOUBLER PWM 24-QFN |
| 标准包装： | 73 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 810kHz |
| 占空比： | 99% |
| 电源电压： | 2.7 V ~ 38 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 是 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 24-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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LTC3852
APPLICATIONS INFORMATION
Further input noise reduction can be achieved by powering
V IN1 through a very small series inductor as shown in
Figure 12. A 10nH inductor will reject the fast current
notches, thereby presenting a nearly constant current
load to the input power supply. For economy, the 10nH
inductor can be fabricated on the PC board with about
1cm (0.4") of PC board trace.
1cm OF PCB TRACE
provide any more capacitance than a 0.22μF 10V X7R
capacitor available in the same 0603 case. In fact, for the
charge pump, these capacitors can be considered roughly
equivalent. The capacitor manufacturer’s data sheet should
be consulted to ensure the desired capacitance at all temp-
eratures and voltages.
Table 1 shows a list of ceramic capacitor manufacturers
and how to contact them:
10nH
12
V IN1
Table 1.
V IN
0.22μF
2.2μF
11
LTC3852
GND1
AVX
Kemet
www.avx.com
www.kemet.com
Murata
www.murata.com
Figure 12. 10nH Inductor Used for
Additional Input Noise Reduction
3852 F12
Taiyo Yuden
TDK
Vishay
www.t-yuden.com
www.component.tdk.com
www.vishay.com
Flying Capacitor Selection
Warning: A polarized capacitor such as tantalum or
aluminum should never be used for the ?ying capacitor
since its voltage can reverse upon start-up of the
charge pump. Low ESR ceramic capacitors should always
be used for the ?ying capacitor.
The ?ying capacitor controls the strength of the charge
pump. In order to achieve the rated output current, it is
necessary to have at least 1μF of capacitance for the ?ying
capacitor.
Ceramic Capacitors
Ceramic capacitors of different materials lose their capac-
itance with higher temperature and voltage at different rates.
For example, a capacitor made of X5R or X7R material
will retain most of its capacitance from –40°C to 85°C
whereas a Z5U or Y5V style capacitor will lose considerable
capacitance over that range. Z5U and Y5V capacitors
may also have a poor voltage coef?cient causing them
to lose 60% or more of their capacitance when the rated
voltage is applied. Therefore when comparing different
capacitors, it is often more appropriate to compare the
amount of achievable capacitance for a given case size
rather than discussing the speci?ed capacitance value. For
example, over rated voltage and temperature conditions,
a 1μF 10V Y5V ceramic capacitor in a 0603 case may not
Ef?ciency Considerations
The percent ef?ciency of a switching regulator is equal to
the output power divided by the input power times 100. It
is often useful to analyze the individual loss components
to determine what limits the ef?ciency and which change
would produce the biggest improvement. The ef?ciency
can be expressed as:
% Ef?ciency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc. are the individual losses as a percentage
of input power.
Although all dissipative elements in the circuit produce
losses, there are ?ve main sources of power loss in
LTC3851 circuits: 1) I 2 R losses, 2) transition losses in the
top MOSFET, 3) gate charge losses within the controller
due to the input capacitance of the power MOSFETs,
4) the DC bias current of the controller (V IN2 ), and 5) the
ef?ciency of the charge pump.
1. I 2 R losses are predicted from the DC resistances of the
fuse (if used), top and bottom MOSFET on-resistances,
the inductor DCR and the current sense resistor (if used).
In continuous conduction mode (CCM), the average
output current ?ows through the inductor (L) and sense
resistor (R SENSE ), but is “chopped” between the top
and bottom MOSFETs. Since the two MOSFETs rarely
have the same R ON , an effective MOSFET resistance
3852f
24
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| LTC3852IUDD#PBF | 功能描述:IC REG CTRLR DOUBLER PWM 24-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3852IUDD#TRPBF | 功能描述:IC REG CTRLR DOUBLER PWM 24-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3853EUJ#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC3853EUJ#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC3853EUJPBF | 制造商:Linear Technology 功能描述:DC-DC Controller Triple Buck 24V QFN40 |
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