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| 型号： | LT3991EMSE-5#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V 1.2A 10-MSOP |
| 标准包装： | 50 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 4.3 V ~ 55 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 200kHz ~ 2MHz |
| 电流 - 输出： | 1.2A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 10-MSOP 裸露焊盘 |
LT3991/LT3991-3.3/LT3991-5
APPLICATIONS INFORMATION
Table 4. Schottky Diodes. The Reverse Current Values Listed Are
Estimates Based Off of Typical Curves for Reverse Current
vs Reverse Voltage at 25°C.
I R at V R =
V R I AVE V F at 1A V F at 2A 20V 25°C
PART NUMBER (V) (A) (mV) (mV) (μA)
On Semiconductor
MBR0520L 20 0.5 30
MBR0540 40 0.5 620 0.4
Schottky diodes often have larger forward voltage drops
at a given current, so a trade-off can exist between low
load and high load efficiency. Often Schottky diodes with
larger reverse bias ratings will have less leakage at a given
output voltage than a diode with a smaller reverse bias
rating. Therefore, superior leakage performance can be
achieved at the expense of diode size. Table 4 lists several
Schottky diodes and their manufacturers.
MBRM120E
MBRM140
Diodes Inc.
B0530W
B0540W
B120
B130
B140
B150
B220
B230
B140HB
DFLS240L
20
40
30
40
20
30
40
50
20
30
40
40
1
1
0.5
0.5
1
1
1
1
2
2
1
2
530
550
620
500
500
500
700
595
500
500
500
0.5
20
15
1
1.1
1.1
1.1
0.4
20
0.6
1
4
Ceramic Capacitors
Ceramic capacitors are small, robust and have very low
ESR. However, ceramic capacitors can cause problems
when used with the LT3991 due to their piezoelectric nature.
When in Burst Mode operation, the LT3991’s switching
frequency depends on the load current, and at very light
loads the LT3991 can excite the ceramic capacitor at audio
frequencies, generating audible noise. Since the LT3991
operates at a lower current limit during Burst Mode op-
eration, the noise is typically very quiet to a casual ear. If
this is unacceptable, use a high performance tantalum or
electrolytic capacitor at the output.
DFLS140 40
DFLS160 60
DFLS2100 100
B240 40
Central Semiconductor
CMSH1 - 40M 40
CMSH1 - 60M 60
CMSH1 - 40ML 40
CMSH2 - 40M
40
CMSH2 - 60M
60
1.1
1
2
2
1
1
1
2
2
510
500
770
500
700
400
860
500
550
700
1
2.5
0.01
0.45
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LT3991. As pre-
viously mentioned, a ceramic input capacitor combined
with trace or cable inductance forms a high quality (under
damped) tank circuit. If the LT3991 circuit is plugged into a
live supply, the input voltage can ring to twice its nominal
value, possibly exceeding the LT3991’s rating. This situation
is easily avoided (see the Hot Plugging Safely section).
BOOST and BD Pin Considerations
CMSH2 - 40L 40 2 400
CMSH2 - 40 40 2 500
CMSH2 - 60M 60 2 700
An additional consideration is reverse leakage current.
When the catch diode is reversed biased, any leakage
current will appear as load current. When operating under
light load conditions, the low supply current consumed
by the LT3991 will be optimized by using a catch diode
with minimum reverse leakage current. Low leakage
14
Capacitor C3 and the internal boost Schottky diode (see
the Block Diagram) are used to generate a boost volt-
age that is higher than the input voltage. In most cases
a 0.47μF capacitor will work well. Figure 3 shows three
ways to arrange the boost circuit. The BOOST pin must
be more than 2.3V above the SW pin for best efficiency.
For outputs of 3V and above, the standard circuit (Figure 3a)
is best. For outputs between 2.8V and 3V, use a 1μF boost
capacitor. A 2.5V output presents a special case because it
is marginally adequate to support the boosted drive stage
3991fa
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| LT3991IDD#PBF | 功能描述:IC REG BUCK ADJ 1.2A 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 产品培训模块:MIC23xxx HyperLight Load™ Regulators 标准包装:5,000 系列:HyperLight Load® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.8V 输入电压:2.7 V ~ 5.5 V PWM 型:混合物 频率 - 开关:4MHz 电流 - 输出:2A 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘，8-MLF? 包装:带卷 (TR) 供应商设备封装:8-MLF?（2x2） 产品目录页面:1094 (CN2011-ZH PDF) 其它名称:576-3303-2 |
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| LT3991IDDPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:55V, 1.2A Step-Down Regulator with 2.8 Quiescent Current |
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