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| 型号： | LM34919BTL |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, PBGA10 |
| 封装： | MICRO, SMD-10 |
| 文件页数： | 3/20页 |
| 文件大小： | 488K |
| 代理商： | LM34919BTL |
30102734
FIGURE 1. Start Up Sequence
Functional Description
The LM34919B Step Down Switching Regulator features all
the functions needed to implement a low cost, efficient buck
bias power converter capable of supplying at least 0.6A to the
load. This high voltage regulator contains an N-Channel buck
switch, is easy to implement, and is available in micro SMD
package. The regulator’s operation is based on a constant on-
time control scheme, where the on-time is determined by
V
IN. This feature allows the operating frequency to remain
relatively constant with load and input voltage variations. The
feedback control requires no loop compensation resulting in
very fast load transient response. The valley current limit de-
tection circuit, internally set at 0.64A, holds the buck switch
off until the high current level subsides. This scheme protects
against excessively high current if the output is short-circuited
when V
IN is high.
The LM34919B can be applied in numerous applications to
efficiently regulate down higher voltages. Additional features
include: Thermal shutdown, V
CC under-voltage lockout, gate
drive under-voltage lockout, and maximum duty cycle limiter.
Control Circuit Overview
The LM34919B buck DC-DC regulator employs a control
scheme based on a comparator and a one-shot on-timer, with
the output voltage feedback (FB) compared to an internal ref-
erence (2.5V). If the FB voltage is below the reference the
buck switch is turned on for a time period determined by the
input voltage and a programming resistor (R
ON). Following the
on-time the switch remains off until the FB voltage falls below
the reference but not less than the minimum off-time. The
buck switch then turns on for another on-time period. Typi-
cally, during start-up, or when the load current increases
suddenly, the off-times are at the minimum. Once regulation
is established, the off-times are longer.
When in regulation, the LM34919B operates in continuous
conduction mode at heavy load currents and discontinuous
conduction mode at light load currents. In continuous con-
duction mode current always flows through the inductor, nev-
er reaching zero during the off-time. In this mode the
operating frequency remains relatively constant with load and
line variations. The minimum load current for continuous con-
11
www.national.com
LM34919B
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM34919BTL/NOPB | 功能描述:直流/直流开关调节器 RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| LM34919BTLX | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator |
| LM34919BTLX/NOPB | 功能描述:直流/直流开关调节器 RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| LM34919C-Q1 | 制造商:TI 制造商全称:Texas Instruments 功能描述:LM34919C-Q1 Ultra Small 50V, 600 mA Constant On-Time Buck Switching Regulator |
| LM34919CQSD/NOPB | 制造商:Texas Instruments 功能描述:IC REG BUCK ADJ 0.6A 12WSON |
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