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参数资料
| 型号： | LT1938IDD#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 4 A SWITCHING REGULATOR, 3300 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封装： | 3 X 3 MM, LEAD FREE, PLASTIC, MO-229WEED-2, DFN-10 |
| 文件页数： | 9/24页 |
| 文件大小： | 260K |
| 代理商： | LT1938IDD#PBF |
LT1938
17
1938fa
Hot Plugging Safely
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypasscapacitorofLT1938circuits.However,thesecapaci-
tors can cause problems if the LT1938 is plugged into a
live supply (see Linear Technology Application Note 88 for
a complete discussion). The low loss ceramic capacitor,
combined with stray inductance in series with the power
source, forms an under damped tank circuit, and the
voltage at the VIN pin of the LT1938 can ring to twice the
nominal input voltage, possibly exceeding the LT1938’s
rating and damaging the part. If the input supply is poorly
controlled or the user will be plugging the LT1938 into an
energized supply, the input network should be designed
to prevent this overshoot. Figure 9 shows the waveforms
that result when an LT1938 circuit is connected to a 24V
supply through six feet of 24-gauge twisted pair. The
first plot is the response with a 4.7F ceramic capacitor
at the input. The input voltage rings as high as 50V and
the input current peaks at 26A. A good solution is shown
in Figure 9b. A 0.7Ω resistor is added in series with the
APPLICATIONS INFORMATION
Figure 8. A Good PCB Layout Ensures Proper, Low EMI Operation
VIAS TO LOCAL GROUND PLANE
VIAS TO VOUT
VIAS TO RUN/SS
VIAS TO PG
VIAS TO VIN
OUTLINE OF LOCAL
GROUND PLANE
1938 F08
L1
C2
RRT
RPG
RC
R2
R1
CC
VOUT
D1
C1
GND
input to eliminate the voltage overshoot (it also reduces
the peak input current). A 0.1F capacitor improves high
frequency filtering. For high input voltages its impact on
efficiency is minor, reducing efficiency by 1.5 percent for
a 5V output at full load operating from 24V.
High Temperature Considerations
The PCB must provide heat sinking to keep the LT1938
cool. The Exposed Pad on the bottom of the package must
be soldered to a ground plane. This ground should be tied
to large copper layers below with thermal vias; these lay-
ers will spread the heat dissipated by the LT1938. Place
additional vias can reduce thermal resistance further. With
these steps, the thermal resistance from die (or junction)
to ambient can be reduced to
θJA = 35°C/W or less. With
100 LFPM airflow, this resistance can fall by another 25%.
Further increases in airflow will lead to lower thermal re-
sistance. Because of the large output current capability of
the LT1938, it is possible to dissipate enough heat to raise
thejunctiontemperaturebeyondtheabsolutemaximumof
125°C. When operating at high ambient temperatures, the
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1939 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller |
| LT1939EDD#PBF | 功能描述:IC REG DL BUCK/LINEAR 12DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
| LT1939EDD#TRPBF | 功能描述:IC REG DL BUCK/LINEAR 12DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
| LT1939EDD-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller |
| LT1939EDD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller |
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