參數(shù)資料
型號(hào)： LTC3833EUDC#PBF
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PQCC20
封裝： 3 X 3 MM, LEAD FREE, PLASTIC, QFN-20
文件頁(yè)數(shù)： 18/36頁(yè)
文件大?。?/td> 513K
代理商： LTC3833EUDC#PBF
LTC3833
25
3833f
APPLICATIONS INFORMATION
The gain of the loop increases with RITHandthebandwidth
of the loop increases with decreasing CITH1. If RITH is
increased by the same factor that CITH1 is decreased, the
zero frequency will be kept the same, thereby keeping the
phase the same in the most critical frequency range of the
feedbackloop.Inaddition,afeedforwardcapacitor,CFF,can
beaddedtoimprovethehighfrequencyresponse,asshown
in Figure 1. Capacitor CFF provides phase lead by creating
a high frequency zero with RFB2 which improves the phase
margin. The output voltage settling behavior is related to
thestabilityoftheclosed-loopsystemandwilldemonstrate
overall performance of the step-down regulator.
Insomeapplications,amoreseveretransientcanbecaused
by switching in loads with large (>10μF) input capacitors.
If the switch connecting the load has low resistance and
is driven quickly, then the discharged input capacitors are
effectively put in parallel with COUT,causingarapiddropin
VOUT. No regulator can deliver enough current to prevent
this problem. The solution is to limit the turn-on speed of
the load switch driver. A Hot Swap controller is designed
specifically for this purpose and usually incorporates cur-
rent limiting, short-circuit protection and soft starting.
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 most 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, four main sources account for
most of the losses:
1. I2R losses. These arise from the resistances of the
MOSFETs, inductor and PC board traces and cause
the efficiency to drop at high output currents. In
continuous mode the average output current flows
though the inductor L, but is chopped between the
top and bottom MOSFETs. If the two MOSFETs have
approximately the same RDS(ON), then the resistance
of one MOSFET can simply by summed with the re-
sistances of L and the board traces to obtain the DC
I2R loss. For example, if RDS(ON) = 0.01Ω and RL =
0.005Ω, the loss will range from 15mW to 1.5W as
the output current varies from 1A to 10A.
2. Transition loss. This loss arises from the brief amount
of time the top MOSFET spends in the saturated region
during switch node transitions. It depends upon the
inputvoltage,loadcurrent,driverstrengthandMOSFET
capacitance,amongotherfactors.Thelossissignificant
at input voltages above 20V.
3. INTVCC current. This is the sum of the MOSFET driver
and control currents. The MOSFET driver current re-
sults from switching the gate capacitance of the power
MOSFETs. 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
controller IQ current. In continuous mode, IGATECHG =
f(Qg(TOP)+Qg(BOT)),whereQg(TOP)andQg(BOT)arethe
gate charges of the topside and bottom side MOSFETs,
respectively.
Supplying INTVCC power through EXTVCC could save
severalpointsofefficiency,especiallyforhighVINappli-
cations.ConnectingEXTVCCtoanoutput-derivedsource
will scale the VIN current required for the driver and
controller circuits by a factor of Duty Cycle/Efficiency.
Forexample,ina20Vto5Vapplication,10mAofINTVCC
current results in approximately 2.5mA of VIN current.
This reduces the mid-current loss from 10% or more
(if the driver was powered directly from VIN) to only a
few percent.
4. CIN loss. The input capacitor has the difficult job of
filtering the large RMS input current to the regulator. It
must have a very low ESR to minimize the AC I2R loss
and sufficient capacitance to prevent the RMS current
from causing additional upstream losses in cabling,
fuses or batteries.
Other losses, which include the COUT ESR loss, bottom
MOSFET reverse-recovery loss and inductor core loss
generally account for less than 2% additional loss.
相關(guān)PDF資料
PDF描述
LTC3833IFE#PBF SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PDSO20
LTC3835IGN-1#TR 3 A SWITCHING CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PDSO16
LTC3835EDHC-1#TRPBF 3 A SWITCHING CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PDSO16
LTC3835IGN-1 3 A SWITCHING CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PDSO16
LTC3835IUFD 3 A SWITCHING CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PQCC20
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC3833IFE#PBF 功能描述:IC REG CTRLR BUCK PWM CM 20TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC3833IFE#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 20TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC3833IUDC#PBF 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC3833IUDC#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC3834EDHC-1#PBF 功能描述:IC REG CTRLR BUCK PWM CM 16-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無(wú) 升壓:是 回掃:是 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR)
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