参数资料
| 型号： | LTC3785EUF#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM VM 24-QFN |
| 标准包装： | 91 |
| PWM 型： | 电压模式 |
| 输出数： | 2 |
| 频率 - 最大： | 1MHz |
| 占空比： | 99% |
| 电源电压： | 2.7 V ~ 10 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 ~ 85°C |
| 封装/外壳： | 24-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
LTC3785
APPLICATIONS INFORMATION
( ) 2 ? ( ) ? 100 = 0.67μH
L >
500 ? 10 3 ? 3 ? 40 ? ( 3.3 )
3.3 ? ( 10 – 3.3 ) ? 100
500 ? 10 3 ? 3 ? 40 ? 10
EFFICIENCYCONSIDERATIONS
The percentage efficiency of a switching regulator is
equal to the output power divided by the input power
times 100%.
It is often useful to analyze individual losses to determine
what is limiting the efficiency and which change would
produce the most improvement. Although all dissipative
elements in circuits produce losses, four main sources
account for most of the losses in LTC3785 application
circuits:
1. DC I 2 R losses. These arise from the resistances of the
MOSFETs, sensing resistor (if used), inductor and PC
board traces and cause the efficiency to drop at high
output currents.
2. Transition loss. This loss arises from the brief voltage
transition time of switch A or switch C. It depends upon
the switch voltage, inductor current, driver strength and
MOSFET capacitance, among other factors.
Transition Loss ~ V SW2 ? I L ? C RSS ? f
where C RSS is the reverse transfer capacitance.
3. C IN and C OUT loss. The input capacitor has the difficult
job of filtering the large RMS input current to the regula-
tor in buck mode. The output capacitor has the more
difficult job of filtering the large RMS output current
in boost mode. Both C IN and C OUT are required to have
low ESR to minimize the AC I 2 R loss and sufficient
capacitance to prevent the RMS current from causing
additional upstream losses in fuses or batteries.
4. Other losses. Optional Schottky diodes D1 and D2 are
responsible for conduction losses during dead time
and light load conduction periods. Core loss is the
predominant inductor loss at light loads. Turning on
switch C causes reverse recovery current loss in boost
mode. When making adjustments to improve efficiency,
the input current is the best indicator of changes in
efficiency. If you make a change and the input current
decreases, then the efficiency has increased. If there
is no change in input current, then there is no change
in efficiency.
5. V CC regulator loss. In applications where the input
voltage is above 5V, such as two Li-Ion cells, the V CC
regulator will dissipate some power due the differential
voltage and the average output current to the drive the
gates of the output switches. The V CC pin can be driven
directly from a high efficiency external 5V source if
desired to incrementally improve overall efficiency at
lighter loads.
DESIGN EXAMPLE
As a design example, assume V IN = 2.7V to 10V (3.6V
nominal Li-Ion with 9V adapter), V OUT = 3.3V (5%),
I OUT(MAX) = 3A and f = 500kHz.
Determine the Inductor Value
Setting the Inductor Ripple to 40% and using the equations
in the Inductor Selection section gives:
2.7 3.3 – 2.7
2
L > = 3.7μH
So the worst-case ripple for this application is during buck
mode so a standard inductor value of 3.3μH is chosen.
3785fc
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3785IUF#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:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
| LTC3785IUF#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 |
| LTC3786EMSE#PBF | 功能描述:IC REG CTRLR BST PWM CM 16-MSOP 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 |
| LTC3786EMSE#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 550kHz MSOP16 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 550kHz, MSOP16 |
| LTC3786EMSE#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 16-MSOP 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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