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| 型号： | LT1940EFE |
| 厂商： | Linear Technology |
| 文件页数： | 16/20页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1.4A DL 16TSSOP |
| 标准包装： | 95 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 1.25 V ~ 22 V |
| 输入电压： | 3.6 V ~ 25 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 1.1MHz |
| 电流 - 输出： | 1.4A |
| 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： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 16-TSSOP-EP |
LT1940/LT1940L
APPLICATIO S I FOR ATIO
capacitors. Although two inductors are required, each will
be smaller than the inductor required for a single-phase
regulator. This may be important when there are tight
height restrictions on the circuit. The Typical Applications
section shows circuits with maximum heights of 1.4mm,
1.8mm and 2.1mm.
There is one special consideration regarding the two-
phase circuit. When the difference between the input
voltage and output voltage is less than 2.5V, then the boost
circuits may prevent the two channels from properly
sharing current. If, for example, channel 1 gets started
first, it can supply the load current, while channel 2 never
switches enough current to get its boost capacitor charged.
In this case, channel 1 will supply the load until it reaches
current limit, the output voltage drops, and channel 2 gets
started. The solution is to generate a boost supply gener-
ated from either SW pin that will service both BOOST pins.
The low profile, single output 5V to 3.3V converter shown
in the Typical Applications section shows how to do this.
Generating an Output Under 1.25V
The LT1940 regulates its feedback pins to 1.25V. Two
resistors can be used to program an output that is higher
than 1.25V. Generating an output voltage that is less than
the internal reference is generally more difficult, but the
LT1940 can easily generate an output voltage less than
1.25V if the other output is greater than 1.25V. Figure 9
shows how.
V OUT1 , which must be greater than 1.25V, is used as a
reference voltage for the feedback divider from V OUT2 to
the FB2 pin (R3 and R4). Calculate the resistor values with
these equations:
R2/R1 = V OUT1 /1.25V - 1
R4/R3 = (1.25V – V OUT2 )/(V OUT1 – 1.25V)
R5 prevents the current through R3 and R4 from pulling
V OUT2 high when there is no load current.
R5 < (R3 + R4) V OUT2 /(V OUT1 – V OUT2 ).
If V OUT1 is out of regulation (during start-up or if it is
overloaded or shorted) then V OUT2 will regulate to a higher
voltage than intended. To avoid this, the power good
output from the channel 1 (PG1) is tied to the compensa-
tion pin (V C2 ) of the channel 2. This disables channel 2
until V OUT1 is in regulation. Accuracy is good, especially
when R4/R3 is small.
For example, for V OUT1 = 3.3V and V OUT2 = 1.2V, choose
R1 = 10k, R2 = 16.5k, R3 = 10k, R4 = 243 ? and R5 = 4.7k.
Other Linear Technology Publications
Application notes AN19, AN35 and AN44 contain more
detailed descriptions and design information for buck
regulators and other switching regulators. The LT1376
data sheet has a more extensive discussion of output
ripple, loop compensation and stability testing. Design
note DN100 shows how to generate a dual (+ and –) output
supply using a buck regulator.
R3
V OUT1
R2
SW1
LT1940
FB2
R4
FB1
SW2
V OUT2
R1
PG1 GND V C2
R5
1940 F09
Figure 9. This circuit can be used when V OUT1 is greater than 1.25V and V OUT2 is less than 1.25V.
1940fa
16
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1940EFE#PBF | 功能描述:IC REG BUCK ADJ 1.4A DL 16TSSOP 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 |
| LT1940EFE#TR | 功能描述:IC REG BUCK ADJ 1.4A DL 16TSSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 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:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT1940EFE#TRPBF | 功能描述:IC REG BUCK ADJ 1.4A DL 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 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:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT1940EFEPBF | 制造商:Linear Technology 功能描述:LT1940 adj 1.4A SD dc-dc converter |
| LT1940LEFE | 功能描述:IC REG BUCK ADJ 1.4A DL 16TSSOP 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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