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参数资料
| 型号： | LT3740EDHC |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 0.14 A SWITCHING CONTROLLER, 330 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | 5 X 3 MM, PLASTIC, MO-229WJED-1, DFN-16 |
| 文件页数： | 2/20页 |
| 文件大小： | 234K |
| 代理商： | LT3740EDHC |
LT3740
10
3740fc
APPLICATIONS INFORMATION
Choose MOSFET Sensing or Resistor Sensing
The LT3740 can use either the bottom MOSFET on-
resistance or an external sensing resistor for current
sensing. Simplicity and high efciency are the benets
of using bottom MOSFET on-resistance. However, some
MOSFETs have a wide on-resistance variation. As discussed
previously, the gate-source voltage and the temperature
also affect the MOSFET on-resistance. These factors affect
the accuracy of the inductor current limit. The inductor
saturation current will need enough margin to cover
the current limit variation. In the cases where the input
voltage supply has sufcient current limit, a wide current
limit variation of the controller may be tolerated. As the
load increases to reach the input supply current limit, the
input voltage corrupts, and limits the total power in the
circuit.
To reduce the current limit variation, a more accurate
external sensing resistor can be used between the bottom
MOSFET source and ground. Connect SN+ and SN– pins
to the two terminals of the resistor.
Power Dissipation
The resulting power dissipation in the MOSFETs are:
PTOP = DTOP IL2 RDS(ON),TOP
PBOT = DBOT IL2 RDS(ON),BOT
If an external sensing resistor is used, the extra power
dissipation in the sensing resistor is:
PRS = DBOT IL2 Rs
The power losses in the bottom MOSFET and external
sensing resistor are greatest during an output short-circuit,
where maximum inductor current and maximum bottom
duty cycle occur.
Besides I2R power loss, there are transition losses and
gate drive losses. The transition losses that increase with
the input voltage and inductor current are mainly in the
top MOSFET. The losses can be estimated with a constant
k = 1.7A–1 as:
Transition Loss = k VIN2 IL CRSS FS
The gate drive losses increase with the gate drive power
supply voltage, gate voltage and gate capacitance as
shown below:
PGD,TOP = VBIAS CGS,TOP VGS,TOP FS
PGD,BOT = VBGDP CGS,BOT VGS,BOT FS
Duty Cycle Limits
At the start of each oscillator cycle, the top MOSFET turns
off and the bottom MOSFET turns on with a 500ns duty
cycle on the top MOSFET. If the maximum duty cycle is
reached, due to a dropping input voltage for example, the
output voltage will droop out of regulation.
Lower ripple current reduces core losses in the inductor,
ESR losses in the output capacitors and output voltage
ripple. The highest efciency is obtained with a small
ripple current. However, achieving this requires a large
inductor. There is a trade off between component size
and efciency.
A reasonable starting point is to choose a ripple current
that is about 30% of IOUT(MAX). The largest ripple current
occurs at the highest VIN. To guarantee that ripple current
does not exceed a specied maximum, the inductance
should be chosen according to:
L
= 1–
V
OUT
V
IN(MAX)
V
OUT
F
S ΔIL(MAX)
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| LT3740EDHC#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LT3740EDHC#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT3740EDHC-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Wide Operating Range, Valley Mode, No RSENSE? Synchronous Step-Down Controller |
| LT3740EDHC-TR | 制造商:LINER 制造商全称:Linear Technology 功能描述:Wide Operating Range, Valley Mode, No RSENSE? Synchronous Step-Down Controller |
| LT3740EDHC-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Wide Operating Range, Valley Mode, No RSENSE? Synchronous Step-Down Controller |
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