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参数资料
| 型号： | LTC3786EMSE#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件页数： | 13/34页 |
| 文件大小： | 397K |
| 代理商： | LTC3786EMSE#PBF |
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LTC3786
20
3786fa
applicaTions inForMaTion
Table 2 summarizes the different states in which the FREQ
pin can be used.
Table 2
FREQ PIN
PLLIN/MODE PIN
FREQUENCY
0V
DC Voltage
350kHz
INTVCC
DC Voltage
535kHz
Resistor
DC Voltage
50kHz to 900kHz
Any of the Above
External Clock
Phase Locked to External Clock
Minimum On-Time Considerations
Minimum on-time, tON(MIN), is the smallest time duration
that the LTC3786 is capable of turning on the bottom
MOSFET. It is determined by internal timing delays and
the gate charge required to turn on the top MOSFET. Low
duty cycle applications may approach this minimum
on-time limit.
In forced continuous mode, if the duty cycle falls below
what can be accommodated by the minimum on-time,
the controller will begin to skip cycles but the output will
continuetoberegulated.Morecycleswillbeskippedwhen
VIN increases. Once VIN rises above VOUT, the loop keeps
the top MOSFET continuously on. The minimum on-time
for the LTC3786 is approximately 110ns.
Efficiency Considerations
The percent 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 greatest improvement. Percent efficiency
can be expressed as:
%Efficiency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc., are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, five main sources usually account for most of the
losses in LTC3786 circuits: 1) IC VBIAS current, 2) INTVCC
regulatorcurrent,3)I2Rlosses,4)BottomMOSFETtransi-
tion losses and 5) Body diode conduction losses.
1. The VBIAS current is the DC supply current given in the
ElectricalCharacteristicstable,whichexcludesMOSFET
driver and control currents. VBIAS current typically
results in a small (<0.1%) loss.
2. INTVCC current is the sum of the MOSFET driver and
control currents. The MOSFET driver current results
from switching the gate capacitance of the power MOS-
FETs. Each time a MOSFET gate is switched from low to
high to low again, a packet of charge, dQ, moves from
INTVCC to ground. The resulting dQ/dt is a current out
of INTVCC that is typically much larger than the control
circuit current. In continuous mode, IGATECHG = f(QT +
QB),whereQTandQBarethegatechargesofthetopside
and bottom side MOSFETs.
3. DC I2R losses. These arise from the resistances of the
MOSFETs, sensing resistor, inductor and PC board
traces and cause the efficiency to drop at high output
currents.
4. Transition losses apply only to the bottom MOSFET(s),
andbecomesignificantonlywhenoperatingatlowinput
voltages. Transition losses can be estimated from:
Transition Loss = 1.7
( )
VOUT3
VIN
IMAX CRSS f
5. Body diode conduction losses are more significant at
higherswitchingfrequency.Duringthedeadtime,theloss
inthetopMOSFETsisILVDS,whereVDSisaround0.7V.
At higher switching frequency, the dead time becomes
a good percentage of switching cycle and causes the
efficiency to drop.
Other hidden losses, such as copper trace and internal
batteryresistances,canaccountforanadditionalefficiency
degradation in portable systems. It is very important to
includethesesystem-levellossesduringthedesignphase.
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相关代理商/技术参数 |
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| LTC3786EUD#PBF | 功能描述:IC REG CTRLR BST PWM CM 16-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 |
| LTC3786EUD#PBF | 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 550kHz, QFN16 |
| LTC3786EUD#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 16-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) |
| LTC3786IMSE#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:- 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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