- 您现在的位置：买卖IC网 > PDF目录44553 > LM3668SD-3.3/NOPB (NATIONAL SEMICONDUCTOR CORP) 2.05 A DUAL SWITCHING CONTROLLER, 2500 kHz SWITCHING FREQ-MAX, DSO12 PDF资料下载
参数资料
| 型号： | LM3668SD-3.3/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 2.05 A DUAL SWITCHING CONTROLLER, 2500 kHz SWITCHING FREQ-MAX, DSO12 |
| 封装： | ROHS COMPLIANT, LLP-12 |
| 文件页数： | 20/20页 |
| 文件大小： | 2497K |
| 代理商： | LM3668SD-3.3/NOPB |
Circuit Description
The LM3668, a high efficiency Buck or Boost DC-DC con-
verter, delivers a constant voltage from either a single Li-Ion
or three cell NIMH/NiCd battery to portable devices such as
mobiles phone and PDAs. Using a voltage mode architec-
tures with synchronous rectification, the LM3668 has the
ability to deliver up to 1A depending on the input voltage, out-
put voltage, ambient temperature and the chosen inductor.
In addition, the device incorporates a seamless transition
from buck to boost or boost to buck mode. The internal error
amplifier continuously monitors the output to determine the
transition from buck to boost or boost to buck operation. Fig-
ure 2 shows the four switches network used for the buck and
boost operation. Table 1 summarizes the state of the swtiches
in different Modes.
There are three modes of operation depending on the current
required: PWM (Pulse Width Modulation), PFM (Pulse Fre-
quency Modulation), and shutdown. The device operates in
PWM mode at load currents of approximately 80mA or higher
to improve efficiency. Lighter load current causes the device
to automatically switch into PFM mode to reduce current con-
sumption and extend battery life. Shutdown mode turns off
the device, offering the lowest current consumption.
20191405
FIGURE 2. Simplified Diagram of Switches
State of Switches in Different Modes
Mode
Always ON
Always
OFF
Switching
Buck
SW P2
SW N2
SW P1 & N1
Boost
SW P1
SW N1
SW N2 & P2
TABLE 1
Buck Operation
When the input voltage is greater than the output voltage, the
device operates in buck mode where switch P2 is always ON
and P1 & N1 control the output . Figure 4 shows the simplified
circuit for buck mode operation.
20191406
FIGURE 3. Simplified Circuit for Buck Operation
Boost Operation
When the input voltage is smaller than the output voltage, the
device enters boost mode operation where P1 is always ON,
while Switches N2 & P2 control the output. Figure 5 shows
the simplified circuit for boost mode operation.
20191408
FIGURE 4. Simplified Circuit for Boost Operation
PWM Operation
In PWM operation, the output voltage is regulated by switch-
ing at a constant frequency and then modulating the energy
per cycle to control power to the load. In Normal operation,
the internal error amplifier provides an error signal, Vc, from
the feedback voltage and Vref. The error amplifier signal, Vc,
is compared with a voltage, Vcenter, and used to generate
the PWM signals for both Buck & Boost Modes. Signal Vcen-
ter is a DC signal which sets the transition point of the buck
and boost modes. Below are three regions of operation:
Region I, If Vc is less than Vcenter, Buck mode.
Region II, If Vc and Vcenter are equal, both PMOS
switches (P1, P2) are on and both NMOS switches (N1,
N2) are off. The power passes directly from input to output
via P1 & P2
Region III, If Vc is greater than Vcenter, Boost Mode.
The Buck-boost operation is avoided, to improve the efficien-
cy across V
IN and load range.
20191415
FIGURE 5. PWM Generator Block Diagram
9
www.national.com
LM3668
相关PDF资料 |
PDF描述 |
|---|---|
| LM368N-5.0 | 1-OUTPUT TWO TERM VOLTAGE REFERENCE, 5 V, PDIP8 |
| LM3691TLX-1.1 | 1.7 A SWITCHING REGULATOR, 4400 kHz SWITCHING FREQ-MAX, PBGA6 |
| LM3691TL-0.85 | 1.7 A SWITCHING REGULATOR, 4400 kHz SWITCHING FREQ-MAX, PBGA6 |
| LM3691TLX-3.3 | 1.7 A SWITCHING REGULATOR, 4400 kHz SWITCHING FREQ-MAX, PBGA6 |
| LM3691TL-1.0 | 1.7 A SWITCHING REGULATOR, 4400 kHz SWITCHING FREQ-MAX, PBGA6 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3668SD-4550 | 制造商:Texas Instruments 功能描述:Conv DC-DC Single Non-Inv/Inv/Step Up/Step Down 2.5V to 5.5V 12-Pin LLP EP T/R |
| LM3668SD-4550/NOPB | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| LM3668SD-4550EV | 功能描述:电源管理IC开发工具 LM3668SD-4550 EVAL BOARD RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| LM3668SDX-2833 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:1A, High Efficiency Dual Mode Single Inductor Buck-Boost DC/DC Converter |
| LM3668SDX-2833/NOPB | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
发布紧急采购，3分钟左右您将得到回复。