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| 型号： | LTC1503IS8-2#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 6/12页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SWITCHD CAP 2V 8SOIC |
| 标准包装： | 2,500 |
| 类型： | 降压（降压），切换电容（充电泵） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 2V |
| 输入电压： | 2.4 V ~ 6 V |
| 频率 - 开关： | 600kHz |
| 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： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-SOIC |
LTC1503-1.8/LTC1503-2
APPLICATIO S I FOR ATIO
General Operation
S4
φ 2
C1 +
S1
φ 1
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.
V IN
C1
(EXTERNAL)
C1 –
S3
φ 2
V OUT
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 V IN . Inductor-based step-
S2
φ 1
1503-1.8/2 F01a
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 V IN and output load conditions. Internal
control circuitry selects the appropriate step-down con-
version ratio based on V IN , V OUT 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 V IN is
greater than two times the desired V OUT . 3-to-2 mode is
chosen when V IN is greater than 1.5 times V OUT but less
than 2 times V OUT . 1-to-1 mode is chosen when V IN falls
below 1.5 times V OUT . 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
V OUT 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
6
Figure 1a. Step-Down Charge Pump in 2-to-1 Mode
S1 and S2 across V OUT . If the voltage on C1 is greater than
the voltage on C OUT , charge is transferred from C1 onto
C OUT . On phase two, the top plate of C1 is connected to V IN
and the bottom plate is connected to V OUT . If the voltage
across C1 is less than V IN /2 during phase two, charge will
be transferred from C1 onto C OUT thereby boosting the
voltage on C OUT and raising the voltage across C1. Thus,
in 2-to-1 mode, charge transfer from C1 onto C OUT occurs
on both phases of the clock, and the voltage on C OUT is
driven towards 1/2V IN 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 V IN , i.e., I VOUT equals approximately 2 ?
I VIN . 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 V OUT . If the
sum of the voltages across C1 and C2 is greater than V OUT ,
charge is transferred from the flying caps onto C OUT
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 V IN and V OUT . Since the average voltage across
the two capacitors during phase one is V OUT /2, charge will
be transferred from V IN to V OUT through the two flying
caps if V IN minus V OUT /2 is greater than V OUT . In this
manner, charge is again transferred from the flying caps
to the output on both phases of the clock, and the voltage
on C OUT is driven towards (2/3)V IN 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. I VOUT in 3-to-2 mode equals
approximately (3/2)I VIN .
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| LTC1504ACS8 | 功能描述:IC REG BUCK SYNC ADJ 0.5A 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 |
| LTC1504ACS8#PBF | 功能描述:IC REG BUCK SYNC ADJ 0.5A 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: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 |
| LTC1504ACS8#TR | 功能描述:IC REG BUCK SYNC ADJ 0.5A 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 |
| LTC1504ACS8#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 0.5A 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: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 |
| LTC1504ACS8-3.3 | 功能描述:IC REG BUCK SYNC 3.3V 0.5A 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 |
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