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参数资料
| 型号： | LT1945IMS#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | DUAL SWITCHING CONTROLLER, PDSO8 |
| 封装： | LEAD FREE, PLASTIC, MSOP-8 |
| 文件页数： | 5/8页 |
| 文件大小： | 121K |
| 代理商： | LT1945IMS#PBF |
LT1945
5
1945fa
APPLICATIONS INFORMATION
Choosing an Inductor
Several recommended inductors that work well with the
LT1945 are listed in Table 1, although there are many other
manufacturers and devices that can be used. Consult each
manufacturer for more detailed information and for their
entire selection of related parts. Many different sizes and
shapes are available. Use the equations and recommenda-
tions in the next few sections to nd the correct inductance
value for your design.
Table 1. Recommended Inductors
PART
VALUE (μH)
MAX DCR (Ω)
VENDOR
LQH3C4R7
LQH3C100
LQH3C220
4.7
10
22
0.26
0.30
0.92
Murata
(714) 852-2001
www.murata.com
CD43-4R7
CD43-100
CDRH4D18-4R7
CDRH4D18-100
4.7
10
4.7
10
0.11
0.18
0.16
0.20
Sumida
(847) 956-0666
www.sumida.com
DO1608-472
DO1608-103
DO1608-223
4.7
10
22
0.09
0.16
0.37
Coilcraft
(847) 639-6400
www.coilcraft.com
Inductor Selection—Boost Regulator
The formula below calculates the appropriate inductor value
to be used for a boost regulator using the LT1945 (or at
least provides a good starting point). This value provides
a good tradeoff in inductor size and system performance.
Pick a standard inductor close to this value. A larger value
can be used to slightly increase the available output current,
but limit it to around twice the value calculated below, as
too large of an inductance will increase the output voltage
ripple without providing much additional output current.
A smaller value can be used (especially for systems with
output voltages greater than 12V) to give a smaller physical
size. Inductance can be calculated as:
L
VV
V
I
t
OUT
IN MIN
D
LIM
OFF
=
+
()
where VD = 0.4V (Schottky diode voltage), ILIM = 350mA
and tOFF = 400ns; for designs with varying VIN such as
battery powered applications, use the minimum VIN value
in the above equation. For most regulators with output
voltages below 7V, a 4.7μH inductor is the best choice,
even though the equation above might specify a smaller
value. This is due to the inductor current overshoot that
occurs when very small inductor values are used (see
Current Limit Overshoot section).
For higher output voltages, the formula above will give large
inductance values. For a 2V to 20V converter (typical LCD
Bias application), a 21μH inductor is called for with the
above equation, but a 10μH inductor could be used without
excessive reduction in maximum output current.
Inductor Selection—SEPIC Regulator
The formula below calculates the approximate inductor
value to be used for a SEPIC regulator using the LT1945.
As for the boost inductor selection, a larger or smaller
value can be used.
L
VV
I
t
OUT
D
LIM
OFF
=
+
2
OPERATION
current in inductors L1 and L2 begins ramping up. Once
the switch current reaches 350mA, comparator A2 resets
the one-shot, which turns off Q3 for 400ns. L2 continues
to deliver current to the output while Q3 is off. Q3 turns on
again and the inductor currents ramp back up to 350mA,
then A2 again resets the one-shot. This switching action
continues until the output voltage is charged up (until the
NFB1 pin reaches –1.23V), then A1 turns off the internal
circuitry and the cycle repeats.
The second switching regulator is a step-up converter
(which generates a positive output) but the basic operation
is the same.The LT1945 contains additional circuitry to
provide protection during start-up and under short-circuit
conditions. When the FB2 pin voltage is less than approxi-
mately 600mV, the switch off-time is increased to 1.5μs
and the current limit is reduced to around 250mA (70%
of its normal value). This reduces the average inductor
current and helps minimize the power dissipation in the
power switch and in the external inductor and diode.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1946 | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.2MHz Boost DC/DC Converter with 1.5A Switch and Soft-Start |
| LT1946/LT1946A | 制造商:LINER 制造商全称:Linear Technology 功能描述:4A, 2MHz Dual Phase Step-Up DC/DC Converter in 3mm 3mm DFN |
| LT1946A | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.2MHz Step-Up DC/DC Converter in SOT-23 |
| LT1946AEMS8E | 功能描述:IC REG BOOST ADJ 1.5A 8MSOP 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: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 |
| LT1946AEMS8E#PBF | 功能描述:IC REG BOOST ADJ 1.5A 8MSOP 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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