参数资料
| 型号： | LT1776IS8#TR |
| 厂商： | Linear Technology |
| 文件页数： | 7/20页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.7A 8SOIC |
| 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： | 1.24 V ~ 34 V |
| 输入电压： | 7.4 V ~ 40 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 200kHz |
| 电流 - 输出： | 700mA |
| 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： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-SOIC |
LT1776
TI M I N G DIAGRA M S
High dV/dt Mode
V IN
V SW
0
SWDR
SWON
BOOST
SWOFF
1776 TD01
OPERATIO
The LT1776 is a current mode switching regulator IC that
has been optimized for high efficiency operation in high
input voltage, low output voltage buck topologies. The
Block Diagram shows an overall view of the system.
Several of the blocks are straightforward and similar to
those found in traditional designs, including: Internal Bias
Regulator, Oscillator and Feedback Amplifier. The novel
portion includes an elaborate Output Switch section and
Logic Section to provide the control signals required by
the switch section.
The LT1776 operates much the same as traditional
current mode switchers, the major difference being its
specialized output switch section. Due to space con-
straints, this discussion will not reiterate the basics of
current mode switcher/controllers and the “buck” topol-
ogy. A good source of information on these topics is
Application Note 19.
Output Switch Theory
One of the classic problems in delivering low output
voltage from high input voltage at good efficiency is that
minimizing AC switching losses requires very fast volt-
age (dV/dt) and current (dI/dt) transition at the output
device. This is in spite of the fact that in a bipolar
Low dV/dt Mode
V IN
V SW
0
SWDR
SWON
BOOST
SWOFF
1776 TD02
Fast positive-going slew rate action is provided by lateral
PNP Q3 driving the Darlington arrangement of Q1 and Q2.
The extra β available from Q2 greatly reduces the drive
requirements of Q3.
Although desirable for dynamic reasons, this topology
alone will yield a large DC forward voltage drop. A second
lateral PNP, Q4, acts directly on the base of Q1 to reduce
the voltage drop after the slewing phase has taken place.
To achieve the desired high slew rate, PNPs Q3 and Q4 are
“force-fed” packets of charge via the current sources
controlled by the boost signal.
Please refer to the High dV/dt Mode Timing Diagram. A
typical oscillator cycle is as follows: The logic section first
generates an SWDR signal that powers up the current
comparator and allows it time to settle. About 1 μ s later, the
SWON signal is asserted and the BOOST signal is pulsed
for a few hundred nanoseconds. After a short delay, the
V SW pin slews rapidly to V IN . Later, after the peak switch
current indicated by the control voltage V C has been
reached (current mode control), the SWON and SWDR
signals are turned off, and SWOFF is pulsed for several
hundred nanoseconds. The use of an explicit turn-off
device, i.e., Q5, improves turn-off response time and thus
aids both controllability and efficiency.
implementation, slow lateral PNPs must be included in
the switching signal path.
7
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1777 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Low Noise Step-Down Switching Regulator |
| LT1777C | 制造商:LINER 制造商全称:Linear Technology 功能描述:Low Noise Step-Down Switching Regulator |
| LT1777CS | 功能描述:IC REG BUCK ADJ 0.7A 16SOIC RoHS:否 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:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LT1777CS#PBF | 功能描述:IC REG BUCK ADJ 0.7A 16SOIC 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:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LT1777CS#TR | 功能描述:IC REG BUCK ADJ 0.7A 16SOIC RoHS:否 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:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
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