参数资料
| 型号： | LT1938IDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 2.2A 10DFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.27 V ~ 20 V |
| 输入电压： | 3.6 V ~ 25 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 300kHz ~ 2.8MHz |
| 电流 - 输出： | 2.2A |
| 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-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-DFN（3x3） |
LT1938
APPLICATIONS INFORMATION
BD
V OUT
6.0
5.5
TO START
V IN
V IN
BOOST
LT1938
C3
5.0
4.5
4.7μF
GND
SW
4.0
3.5
TO RUN
(4a) For V OUT > 2.8V
BD
D2
V OUT
3.0
2.5
2.0
0.001
0.01 0.1
LOAD CURRENT (A)
V OUT = 3.3V
T A = 25°C
L = 4.7μH
f = 800kHz
1 10
V IN
4.7μF
V IN
BOOST
LT1938
SW
GND
C3
8.0
7.0
6.0
TO START
5.0
TO RUN
(4b) For 2.5V < V OUT < 2.8V
4.0
BD
BOOST
V OUT
3.0
2.0
0.001
0.01
0.1
V OUT = 5V
T A = 25°C
L = 4.7μH
f = 800kHz
1
10
V IN
V IN
LT1938
C3
LOAD CURRENT (A)
1938 F05
4.7μF
GND
SW
Figure 5. The Minimum Input Voltage Depends on
Output Voltage, Load Current and Boost Circuit
1938 F04
(4c) For V OUT < 2.5V
Figure 4. Three Circuits For Generating The Boost Voltage
proper start-up, the minimum input voltage is also limited
by the boost circuit. If the input voltage is ramped slowly,
or the LT1938 is turned on with its RUN/SS pin when the
output is already in regulation, then the boost capacitor
may not be fully charged. Because the boost capacitor is
charged with the energy stored in the inductor, the circuit
will rely on some minimum load current to get the boost
circuit running properly. This minimum load will depend
on input and output voltages, and on the arrangement of
the boost circuit. The minimum load generally goes to
zero once the circuit has started. Figure 5 shows a plot
of minimum load to start and to run as a function of input
voltage. In many cases the discharged output capacitor
will present a load to the switcher and the minimum input
to start will be the same as the minimum input to run.
This occurs, for example, if RUN/SS is asserted after V IN
is applied. The plots show the worst-case situation where
V IN is ramping very slowly. For lower start-up voltage, the
boost diode can be tied to V IN ; however, this restricts the
input range to one-half of the absolute maximum rating
of the BOOST pin.
At light loads, the inductor current becomes discontinu-
ous and the effective duty cycle can be very high. This
reduces the minimum input voltage to approximately
300mV above V OUT . At higher load currents, the inductor
current is continuous and the duty cycle is limited by the
maximum duty cycle of the LT1938, requiring a higher
input voltage to maintain regulation.
1938fa
15
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| 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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