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参数资料
| 型号： | LTC3780IG#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 19/30页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 24-SSOP |
| 标准包装： | 1,800 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 440kHz |
| 占空比： | 99% |
| 电源电压： | 4 V ~ 36 V |
| 降压： | 是 |
| 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-SSOP（0.209"，5.30mm 宽） |
| 包装： | 带卷 (TR) |
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LTC3780
APPLICATIONS INFORMATION
? I OUT ( MAX ) 2 ? ρ T ? R DS ( ON )
P B , BUCK =
Power MOSFET Selection and
Efficiency Considerations
The LTC3780 requires four external N-channel power MOS-
FETs, two for the top switches (switch A and D, shown in
Figure 1) and two for the bottom switches (switch B and C
shown in Figure 1). Important parameters for the power
MOSFETs are the breakdown voltage V BR,DSS , threshold
voltage V GS,TH , on-resistance R DS(ON) , reverse transfer
capacitance C RSS and maximum current I DS(MAX) .
Switch B operates in buck mode as the synchronous
rectifier. Its power dissipation at maximum output current
is given by:
V IN – V OUT
V IN
Switch C operates in boost mode as the control switch.
Its power dissipation at maximum current is given by:
( V OUT – V IN ) V OUT ? I
? ρ T ? R DS ( ON )
V IN 2
+ k ? V OUT 3 ?
I OUT ( MAX )
? C RSS ? f
The drive voltage is set by the 6V INTV CC supply. Con-
sequently, logic-level threshold MOSFETs must be used
in LTC3780 applications. If the input voltage is expected
to drop below 5V, then the sub-logic threshold MOSFETs
should be considered.
P C , BOOST =
V IN
2
OUT ( MAX )
? V
?
P A , BOOST = ? OUT ? I OUT ( MAX ) ? ? ρ T ? R DS ( ON )
? V
?
V IN
P D , BOOST = ? ? OUT ? I OUT ( MAX ) ? ? ρ T ? R DS ( ON )
In order to select the power MOSFETs, the power dis-
sipated by the device must be known. For switch A, the
maximum power dissipation happens in boost mode, when
it remains on all the time. Its maximum power dissipation
at maximum output current is given by:
2
? V IN ?
where ρ T is a normalization factor (unity at 25°C) ac-
counting for the significant variation in on-resistance with
temperature, typically about 0.4%/°C as shown in Figure 9.
For a maximum junction temperature of 125°C, using a
value ρ T = 1.5 is reasonable.
2.0
1.5
1.0
where C RSS is usually specified by the MOSFET manufactur-
ers. The constant k, which accounts for the loss caused
by reverse recovery current, is inversely proportional to
the gate drive current and has an empirical value of 1.7.
For switch D, the maximum power dissipation happens in
boost mode, when its duty cycle is higher than 50%. Its
maximum power dissipation at maximum output current
is given by:
2
V OUT ? V IN ?
For the same output voltage and current, switch A has the
highest power dissipation and switch B has the lowest
power dissipation unless a short occurs at the output.
From a known power dissipated in the power MOSFET, its
junction temperature can be obtained using the following
formula:
T J = T A + P ? R TH(JA)
0.5
0
–50
0 50 100
JUNCTION TEMPERATURE (°C)
150
The R TH(JA) to be used in the equation normally includes
the R TH(JC) for the device plus the thermal resistance from
the case to the ambient temperature (R TH(JC) ). This value
of T J can then be compared to the original, assumed value
used in the iterative calculation process.
3780 F09
Figure 9. Normalized R DS(ON) vs Temperature
3780ff
For more information www.linear.com/LTC3780
19
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3780IUH | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 32-Pin QFN EP |
| LTC3780IUH#PBF | 功能描述:IC REG CTRLR BST PWM CM 32-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 |
| LTC3780IUH#PBF | 制造商:Linear Technology 功能描述:DC/DC Controller IC |
| LTC3780IUH#TR | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 32-Pin QFN EP T/R |
| LTC3780IUH#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 32-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 |
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