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| 型号： | LT3990HMSE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 9/22页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.35A 16MSOP |
| 标准包装： | 37 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.21 V ~ 25 V |
| 输入电压： | 4.2 V ~ 62 V |
| PWM 型： | 电流模式，Burst Mode? |
| 频率 - 开关： | 210kHz ~ 2.3MHz |
| 电流 - 输出： | 350mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 150°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TFSOP（0.118"，3.00mm 宽）裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 16-MSOP，裸露焊盘 |
LT3990/LT3990-3.3/LT3990-5
OPERATION
The LT3990 is a constant frequency, current mode step-
down regulator. An oscillator, with frequency set by RT,
sets an RS flip-flop, turning on the internal power switch.
An amplifier and comparator monitor the current flowing
between the V IN and SW pins, turning the switch off when
this current reaches a level determined by the voltage at
V C (see Block Diagram). An error amplifier measures the
output voltage through an external resistor divider tied to
the FB pin and servos the V C node. If the error amplifier’s
output increases, more current is delivered to the output;
if it decreases, less current is delivered.
Another comparator monitors the current flowing through
the catch diode and reduces the operating frequency when
the current exceeds the 450mA bottom current limit. This
foldback in frequency helps to control the output current
in fault conditions such as a shorted output with high
input voltage. Maximum deliverable current to the output
is therefore limited by both switch current limit and catch
diode current limit.
An internal regulator provides power to the control cir-
cuitry. The bias regulator normally draws power from
the V IN pin, but if the BD pin is connected to an external
voltage higher than 3.2V, bias power will be drawn from
the external source (typically the regulated output voltage).
This improves efficiency.
If the EN/UVLO pin is low, the LT3990 is shut down and
draws 0.7μA from the input. When the EN/UVLO pin ex-
ceeds 1.19V, the switching regulator will become active.
The switch driver operates from either V IN or from the
BOOST pin. An external capacitor is used to generate a
voltage at the BOOST pin that is higher than the input
supply. This allows the driver to fully saturate the internal
bipolar NPN power switch for efficient operation.
To further optimize efficiency, the LT3990 automatically
switches to Burst Mode operation in light load situations.
Between bursts, all circuitry associated with controlling
the output switch is shut down reducing the input supply
current to 1.8μA.
The LT3990 contains a power good comparator which
trips when the FB pin is at 90% of its regulated value. The
PG output is an open-drain transistor that is off when the
output is in regulation, allowing an external resistor to pull
the PG pin high. Power good is valid when the LT3990 is
enabled and V IN is above 4.2V.
3990fa
9
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3990IDD#PBF | 功能描述:IC REG BUCK ADJ 0.35A 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 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:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3990IDD#TRPBF | 功能描述:IC REG BUCK ADJ 0.35A 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 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:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3990IDDB | 制造商:LINER 制造商全称:Linear Technology 功能描述:60V, 350mA Step-Down Regulator with 2.5μA Quiescent Current and Integrated Diodes |
| LT3990IDDBPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:60V, 350mA Step-Down Regulator with 2.5μA Quiescent Current and Integrated Diodes |
| LT3990IDDBTRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:60V, 350mA Step-Down Regulator with 2.5μA Quiescent Current and Integrated Diodes |
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