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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： | 6/20页 |
| 文件大小： | 234K |
| 代理商： | LT3740EDHC |
LT3740
14
3740fc
APPLICATIONS INFORMATION
Selecting a standard value of 2.0μH results in a ripple
current of:
ΔI
L =
2.5V
(300kHz) (2
μH)
1–
2.5V
15V
= 3.47A
Set Range = VIN. At minimum input voltage VIN = 7V,
the maximum current sensing voltage is 145mV. Use an
external sensing resistor of 12mΩ. The inductor current
valley will be clamped to 12A. The ripple current at VIN= 7V
is 2.68A, there is about 33% of margin for the 10A load
current to cover the maximum current sensing voltage
variation.
For the case of using MOSFET on-resistance for current
sensing, choosing a Si4840 (RDS(ON) = 0.008Ω (NOM)
0.0095Ω (MAX) for VGS = 7V, θJA = 40°C/W) yields a
nominal sense voltage of:
VSN(NOM) = (10A)(1.3)(0.0095Ω) =123mV
To check if the current limit is acceptable, assume a junc-
tion temperature of about 55°C above a 70°C ambient
with
ρ125°C = 1.5:
I
LIMIT =
145mV
1.5 0.0095
Ω
+
2.68A
2
= 11.5A
Double check the assumed TJ in the MOSFET at VIN = 7V
with maximum load current:
PBOT = DBOT IL2 RDS(ON), BOT
P
BOT = 1–
2.5V
7V
10A
()2 1.50.0095=0.92W
Double check the assumed TJ in the MOSFET:
TJ = 70°C + (0.92W)(40°C/W) = 107°C
The power dissipation in the bottom MOSFET increases
with input voltage. For VIN = 20V,
P
BOT = 1–
2.5V
20V
10A
()2 1.50.0095Ω=1.25W
Double check the assumed TJ in the MOSFET:
TJ = 70°C + (1.25W)(40°C/W) = 120°C
Choose a Si4840 (CRSS = 200pF) for the top MOSFET and
check its power dissipation at maximum load current with
ρ100°C = 1.3:
P
TOP =
2.5V
20V
10A
()2 1.30.0095Ω+17(20V)2
10A 200pF 300kHz
= 0.15W + 0.41W = 0.56W
TJ = 70°C + (0.56W)(40°C/W) = 92°C
This analysis shows that careful attention to heat sinking
will be necessary in this circuit.
Check the reverse current comparator margin. The maxi-
mum ripple current happens at maximum input voltage:
ΔI
L(MAX) =
2.5V
300kHz 2
μH
1–
2.5V
20V
= 3.65A
At no load, the maximum reverse current voltage is:
R
S
ΔI
L(MAX)
2
= 12mΩ
3.65A
2
= 22mV
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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) |
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