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参数资料
| 型号： | LTC1503CMS8-2#TR |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 电源模块 |
| 英文描述： | 1-OUTPUT DC-DC REG PWR SUPPLY MODULE |
| 封装： | PLASTIC, MSOP-8 |
| 文件页数： | 9/12页 |
| 文件大小： | 187K |
| 代理商： | LTC1503CMS8-2#TR |
6
LTC1503-1.8/LTC1503-2
General Operation
The two most common methods for providing regulated
step-down DC/DC conversion are linear DC/DC conversion
(used by LDOs) and inductor-based DC/DC conversion.
Linear regulation provides low cost and low complexity, but
the conversion efficiency is poor since all of the load cur-
rent must come directly from VIN. Inductor-based step-
down conversion provides the highest efficiency, but the
solution cost and circuit complexity are much higher. The
LTC1503-X provides the efficiency advantages associated
with inductor-based circuits as well as the cost and sim-
plicity advantages of an inductorless converter.
The LTC1503-X is a switched capacitor step-down DC/DC
converter. The part uses an internal switch network and
fractional conversion ratios to achieve high efficiency over
widely varying VIN and output load conditions. Internal
control circuitry selects the appropriate step-down con-
version ratio based on VIN, VOUT and load conditions to
optimize efficiency. The part has three possible step-down
modes: 2-to-1, 3-to-2 or 1-to-1 (gated switch) step-down
mode. Only two external flying caps are needed to operate
in all three modes. 2-to-1 mode is chosen when VIN is
greater than two times the desired VOUT. 3-to-2 mode is
chosen when VIN is greater than 1.5 times VOUT but less
than 2 times VOUT. 1-to-1 mode is chosen when VIN falls
below 1.5 times VOUT. An internal mode skip function will
switch the step-down ratio as needed to maintain output
regulation under heavy load conditions.
Regulation is achieved by sensing the divided down output
voltage and enabling the charge pump as needed to boost
the output back into regulation. This method of regulation
allows the LTC1503-X to achieve high efficiency at very
light loads. The part has shutdown capability as well as
user controlled inrush current limiting. In addition, the
part can withstand an indefinite short-circuit condition on
VOUT and is also overtemperature protected.
Step-Down Charge Pump Operation
Figure 1a shows the charge pump switch configuration
that is used for 2-to-1 step down. When the charge pump
is enabled in this mode, a two phase nonoverlapping clock
generates the switch control signals. On phase one of the
clock, flying capacitor C1 is connected through switches
Figure 1a. Step-Down Charge Pump in 2-to-1 Mode
S1 and S2 across VOUT. If the voltage on C1 is greater than
the voltage on COUT, charge is transferred from C1 onto
COUT. On phase two, the top plate of C1 is connected to VIN
and the bottom plate is connected to VOUT. If the voltage
across C1 is less than VIN/2 during phase two, charge will
be transferred from C1 onto COUT thereby boosting the
voltage on COUT and raising the voltage across C1. Thus,
in 2-to-1 mode, charge transfer from C1 onto COUT occurs
on both phases of the clock, and the voltage on COUT is
driven towards 1/2VIN until the output is back in regula-
tion. Since charge current is sourced from ground on
phase one of the clock, current multiplication is realized
with respect to VIN, i.e., IVOUT equals approximately 2
IVIN. This results in significant efficiency improvement
relative to a linear regulator.
The 3-to-2 conversion mode also uses a nonoverlapping
clock for switch control but requires two flying capacitors
and a total of seven switches (see Figure 1b). On phase
one, C1 and C2 are connected in series across VOUT. If the
sum of the voltages across C1 and C2 is greater than VOUT,
charge is transferred from the flying caps onto COUT
thereby reducing the average voltage on the flying caps
and raising the voltage on the output capacitor. On phase
two, the two flying capacitors are connected on parallel
between VIN and VOUT. Since the average voltage across
the two capacitors during phase one is VOUT/2, charge will
be transferred from VIN to VOUT through the two flying
caps if VIN minus VOUT/2 is greater than VOUT. In this
manner, charge is again transferred from the flying caps
to the output on both phases of the clock, and the voltage
on COUT is driven towards (2/3)VIN until the part is back in
regulation. As in 2-to-1 mode, charge current is sourced
from ground on phase one of the clock which results in
increased power efficiency. IVOUT in 3-to-2 mode equals
approximately (3/2)IVIN.
S4
φ2
S1
φ1
S3
φ2
S2
φ1
C1
(EXTERNAL)
C1+
C1–
1503-1.8/2 F01a
VIN
VOUT
APPLICATIO S I FOR ATIO
WU
UU
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1503CS8-1.8 | 功能描述:IC REG BUCK SWITCHED CAP 8SOIC 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 |
| LTC1503CS8-1.8#PBF | 功能描述:IC REG BUCK SWITCHED CAP 8SOIC 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 |
| LTC1503CS8-1.8#TR | 功能描述:IC REG BUCK SWITCHED CAP 8SOIC 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 |
| LTC1503CS8-1.8#TRPBF | 功能描述:IC REG BUCK SWITCHED CAP 8SOIC 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:500 系列:- 类型:切换式电容器（充电泵），反相 输出类型:固定 输出数:1 输出电压:-3V 输入电压:2.3 V ~ 5.5 V PWM 型:Burst Mode? 频率 - 开关:900kHz 电流 - 输出:100mA 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:SOT-23-6 细型，TSOT-23-6 包装:带卷 (TR) 供应商设备封装:TSOT-23-6 其它名称:LTC1983ES6-3#TRMTR |
| LTC1503CS8-2 | 功能描述:IC REG BUCK SWITCHD CAP 2V 8SOIC 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: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 |
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