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参数资料
| 型号： | LTC3785EUF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 3 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC24 |
| 封装： | 4 X 4 MM, PLASTIC, MO-220WGGD, QFN-24 |
| 文件页数： | 8/20页 |
| 文件大小： | 275K |
| 代理商： | LTC3785EUF |
LTC3785
3785fc
applicaTions inForMaTion
Determine the Proper Inductor Type Selection
The highest inductor current is during boost mode and
is given by:
IL(MAX_ AV) =
VOUT IOUT
VIN η
where
η = estimated efficiency in this mode (use 80%).
IL(MAX_ AV) =
3.3 3
2.7 0.8
= 4.6A
To limit the maximum efficiency loss of the inductor ESR
to below 5% the equation is:
ESRL(MAX) ~
VOUT IOUT %Loss
IL(MAX_ AV)
2 100
= 24mΩ
A suitable inductor for this application could be a Coiltron-
ics CD1-3R8 which has a rating DC current of 6A and ESR
of 13m.
Choose a Proper MOSFET Switch
Using the same guidelines for ESR of the inductor, one
suitable MOSFET could be the Siliconix Si7940DP which
is a dual MOSFET in a surface mount package with 25m
Ω
at 2.5V and a total gate charge of 12nC.
Checking the power dissipation of each switch will ensure
reliable operation since the thermal resistance of the
package is 60°C/W.
The maximum power dissipation of switch A and C oc-
curs in boost mode. Assuming a junction temperature
of TJ = 100°C with ρ100C = 1.3, the power dissipation at
VIN = 2.7, and using the equations from the Efficiency
Considerations section:
PA(BOOST)
=
3.3
2.7
3
2
1.3 0.025
= 0.43W
PC(BOOST)
=
3.3 – 2.7
(
)3.3
2.72
32 1.3 0.025
+ 13.33
3
2.7
0.45 – 9 500 103
= 0.09W
The maximum power dissipation of switch B and D occurs
in buck mode and is given by:
PB(BUCK)
=
10 – 3.3
10
32 1.3 0.025
= 0.20W
PD(BOOST)
=
3.3
10
32 1.3 0.025
= 0.10W
Now to double check the TJ of the package with 50°C
ambient. Since this is a dual NMOS package we can add
switches A + B and C + D worst-case. For applications
wheretheMOSFETsareinseparatepackageseachdevice’s
maximum TJ would have to be calculated.
TJ(PKG1) = TA + θJA(PA + PB)
= 50 + 60 (0.43 + 0.20) = 88°C
TJ(PKG2) = TA + θJA(PC + PD)
= 50 + 60 (0.09 + 0.10) = 60°C
Set The Maximum Current Limit
The equation for setting the maximum current limit of the
IC is given by:
RILSET =
6000
RDS(ON)A ILIMIT
Ω
Themaximumcurrentisset25%aboveIL(PEAK)toaccount
for worst-case variation at 100°C = 6A.
RILSET =
6000
0.025 6
= 42k
Choose the Input and Output Capacitance
The input capacitance should filter current ripple which is
worst-case in buck mode. Since the input current could
reach 6A, a capacitor ESR of 10m
Ω or less will yield an
input ripple of 60mV.
The output capacitance should filter current ripple which
is worst in boost mode, but is usually dictated by the loop
response, the maximum load transient and the allowable
transient response.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3785EUF#PBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN 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 |
| LTC3785EUF#TRPBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN 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) |
| LTC3785EUF-1#PBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN 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) |
| LTC3785EUF-1#TRPBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC3785EUFPBF | 制造商:Linear Technology 功能描述:10V Synch Buck-Boost Controller LTC3785 |
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