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参数资料
| 型号： | LTC3250ES6-1.5#TRM |
| 厂商： | Linear Technology |
| 文件页数： | 7/12页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 1.5V 0.25A SOT23-6 |
| 标准包装： | 1 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 1.5V |
| 输入电压： | 3.1 V ~ 5.5 V |
| PWM 型： | Burst Mode? |
| 频率 - 开关： | 1.5MHz |
| 电流 - 输出： | 250mA |
| 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 |
| 包装： | 剪切带 (CT) |
| 供应商设备封装： | SOT-23-6 |
| 产品目录页面： | 1339 (CN2011-ZH PDF) |
| 其它名称： | LTC3250ES6-1.5 LTC3250ES6-1.5#TRMCT LTC3250ES6-1.5-ND |
LTC3250-1.5/LTC3250-1.2
OPERATIO
(Refer to Simplified Block Diagram)
current. For an ideal 2 to 1 step-down charge pump the
power efficiency is given by:
0.15 ? for the LTC3250-1.5 and 0.12 ? for the
LTC3250-1.2. For a 250mA load current change the output
voltage will change by about 37mV for the LTC3250-1.5
= =
η≡
P OUT
P IN
V OUT ? I OUT
1
V IN ? I OUT
2
2 V OUT
V IN
and by 30mV for the LTC 3250-1.2. If the ESR of the output
capacitor is greater than the closed-loop-output imped-
ance the part will cease to roll-off in a simple one-pole
fashion and poor load transient response or instability
The switching losses and quiescent current of the
LTC3250-1.5/LTC3250-1.2 are designed to minimize effi-
ciency loss over the entire output current range, causing
only a couple % error from the theoritical efficiency. For
example with V IN = 3.6V, I OUT = 100mA and V OUT regulat-
ing to 1.5V the measured efficiency is 80.6% which is in
close agreement with the theoretical 83.3% calculation.
V OUT Capacitor Selection
could result. Ceramic capacitors typically have excep-
tional ESR performance and combined with a tight board
layout should yield excellent stability and load transient
performance.
Further output noise reduction can be achieved by filtering
the LTC3250-1.5/LTC3250-1.2 output through a very small
series inductor as shown in Figure 1. A 10nH inductor will
10nH
The ESR and value of capacitors used with the LTC3250-
1.5/LTC3250-1.2 determine several important parameters
such as regulator control loop stability, output ripple, and
V OUT
LTC3250-1.5/
LTC3250-1.2
(TRACE INDUCTANCE)
4.7 μ F
V OUT
0.22 μ F
charge pump strength.
The value of C OUT directly controls the amount of output
ripple for a given load current. Increasing the size of C OUT
will reduce the output ripple.
To reduce output noise and ripple, it is suggested that a
low ESR (<0.1 ? ) ceramic capacitor (4.7 μ F or greater) be
used for C OUT . Tantalum and aluminum capacitors are not
recommended because of their high ESR.
Both ESR and value of the C OUT can significantly affect the
stability of the LTC3250-1.5/LTC3250-1.2. As shown in
the block diagram, the LTC3250-1.5/LTC3250-1.2 use a
control loop to adjust the strength of the charge pump to
match the current required at the output. The error signal
of this loop is stored directly on the output charge storage
capacitor. Thus the charge storage capacitor also serves
to form the dominant pole for the control loop. To prevent
ringing or instability it is important for the output capacitor
to maintain at least 2.5 μ F of capacitance over all condi-
tions (see “Ceramic Capacitor Selection Guidelines” sec-
tion).
Likewise excessive ESR on the output capacitor will tend
to degrade the loop stability of the LTC3250-1.5/LTC3250-
GND
3250 F01
Figure 1. 10nH Inductor Used for
Additional Output Noise Reduction
reject the fast output transients, thereby presenting a
nearly constant output voltage. For economy the 10nH
inductor can be fabricated on the PC board with about 1cm
(0.4") of PC board trace.
V IN Capacitor Selection
The constant frequency architecture used by the
LTC3250-1.5/LTC3250-1.2 makes input noise filtering
much less demanding than conventional charge pump
regulators. On a cycle by cycle basis, the LTC3250-1.5/
LTC3250-1.2 input current will go from I OUT /2 to 0mA.
Lower ESR will reduce the voltage steps caused by chang-
ing input current, while the absolute capacitor value will
determine the level of ripple. For optimal input noise and
ripple reduction, it is recommended that a low ESR 1 μ F or
greater ceramic capacitor be used for C IN (see “Ceramic
Capacitor Selection Guidelines” section). Aluminum and
tantalum capacitors are not recommended because of
their high ESR.
1.2. The closed-loop output resistance is designed to be
3250fa
7
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相关代理商/技术参数 |
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| LTC3251 | 制造商:LINER 制造商全称:Linear Technology 功能描述:500mA High Efficiency, Low Noise, Inductorless Step-Down DC/DC Converter |
| LTC3251-1.2 | 制造商:LINER 制造商全称:Linear Technology 功能描述:500mA High Efficiency, Low Noise, Inductorless Step-Down DC/DC Converter |
| LTC3251-1.5 | 制造商:LINER 制造商全称:Linear Technology 功能描述:500mA High Efficiency, Low Noise, Inductorless Step-Down DC/DC Converter |
| LTC3251EMSE | 功能描述:IC REG BUCK SWITCHED CAP 10MSOP 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 |
| LTC3251EMSE#PBF | 功能描述:IC REG BUCK SWITCHED CAP 10MSOP 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 |
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