LTC3672B-1
8
3672B1f
OPERATION
LOW DROPOUT LINEAR REGULATORS (LDOS)
The LTC3672B-1 contains two 150mA  xed-output LDO
regulators. LDO1 takes power from the V
IN1
 pin and regu-
lates a 1.2V output at the LDO1 pin. By connecting V
IN1
 
to the buck regulators 1.8V output, overall conversion
ef ciency can be improved, because the bulk of the step-
down will be done by the buck regulator at higher ef ciency
than what the LDO can do on its own. For example, for
the case of deriving a 1.2V output from a 3.6V input (e.g.
Lithium-Ion battery nominal voltage), using an LDO to
do all of the step-down results in an ef ciency of at most
1.2V/3.6V = 33.3%, using the fact that the upper-bound on
any linear regulators ef ciency is output voltage divided by
input voltage. Feeding the LDO from the output of the buck
regulator, with a typical buck ef ciency of 85%, raises the
ceiling on overall ef ciency to 85% " 1.2V/1.8V = 56.6%.
This can increase battery life by up to 70%!
LDO2 takes power straight from V
IN
 and regulates a 2.8V
output at the LDO2 pin.
For stability, each LDO output must be bypassed to ground
with a minimum 1糉 ceramic capacitor.
APPLICATIONS INFORMATION
BUCK REGULATOR INDUCTOR SELECTION
Many different sizes and shapes of inductors are avail-
able from numerous manufacturers. Choosing the right
inductor from such a large selection of devices can be
overwhelming, but following a few basic guidelines will
make the selection process much simpler.
The buck regulator is designed to work with inductors in
the range of 2.2糎 to 10糎. A 4.7糎 inductor is a good
starting point. Larger value inductors reduce ripple cur-
rent, which improves output ripple voltage. Lower value
inductors result in higher ripple current and improved
transient response time. To maximize ef ciency, choose
an inductor with a low DC resistance. Choose an inductor
with a DC current rating at least 1.5 times larger than the
maximum load current to ensure that the inductor does
not saturate during normal operation. If output short circuit
is a possible condition, the inductor should be rated to
handle the maximum peak current speci ed for the step-
down converters.
Different core materials and shapes will change the size/cur-
rent and price/current relationship of an inductor. Toroid
or shielded pot cores in ferrite or Permalloy" materials
are small and dont radiate much energy, but generally
cost more than powdered iron core inductors with similar
electrical characteristics. Inductors that are very thin or
have a very small volume typically have much higher core
and DCR losses, and will not give the best ef ciency. The
choice of which style inductor to use often depends more
on the price vs size, performance, and any radiated EMI
requirements than on what the buck regulator needs to
operate.
Table 1 shows several inductors that work well with the
buck regulator. These inductors offer a good compromise
in current rating, DCR and physical size. Consult each
manufacturer for detailed information on their entire
selection of inductors.
相关PDF资料
LTC3700EMS#TRPBF IC REG DL BUCK/LINEAR 10MSOP
LTC4151HMS#TRPBF IC PWR MONITOR MS 80V SD 10MSOP
LTC4210-2CS6#TRM IC CONTROLLER HOT SWAP TSOT23-6
LTC4211IMS8 IC CONTROLLER HOT SWAP 8-MSOP
LTC4212IMS#TRPBF IC CTRLR HOTSWAP TIMEOUT 10MSOP
LTC4214-1IMS#TRPBF IC CTRLR HOTSWAP NEGVOLT 10MSOP
LTC4215IUFD#PBF IC CNTRLR HOT SWAP 24-QFN
LTC4216IDE#TRPBF IC CNTRLR HOT SWAP 12-DFN
相关代理商/技术参数
LTC3672BEDC-2#TRMPBF 功能描述:IC REG TRPL BCK/LINEAR 8-DFN 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:*
LTC3672BEDC-2#TRPBF 功能描述:IC REG TRPL BCK/LINEAR 8-DFN 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:*
LTC3675EUFF#PBF 功能描述:IC PMIC PWR SUPPLYED DVR 44-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP(4x4) 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR
LTC3675EUFF#TRPBF 功能描述:IC PMIC PWR SUPPLYED DVR 44-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP(4x4) 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR
LTC3675EUFF-1#PBF 制造商:Linear Technology 功能描述:MISC 制造商:Linear Technology 功能描述:IC PWR SUPPLY + LED DRVR 44QFN 制造商:Linear Technology 功能描述:DP-PMIC Multifunction, 8-Channel Configurable High Power PMIC
LTC3675EUFF-1#TRPBF 制造商:Linear Technology 功能描述:7-CHANNEL CONFI GURABLE HIGH POWER PMIC 制造商:Linear Technology 功能描述:IC PWR SUPPLY + LED DRVR 44QFN 制造商:Linear Technology 功能描述:DP-PMIC Multifunction, 8-Channel Configurable High Power PMIC
LTC3676EUJ#PBF 制造商:Linear Technology 功能描述: 制造商:Linear Technology 功能描述:DP-PMIC Multifunction, PMIC For Applications Processors
LTC3676EUJ-1#PBF 制造商:Linear Technology 功能描述:IC CONV I.MX6 40QFN 制造商:Linear Technology 功能描述:DP-PMIC Multifunction, PMIC For Applications Processors