參數(shù)資料
型號(hào)： LTC3809EMS-1
廠商： LINEAR TECHNOLOGY CORP
元件分類(lèi)： 穩(wěn)壓器
英文描述： 1 A SWITCHING CONTROLLER, 600 kHz SWITCHING FREQ-MAX, PDSO10
封裝： PLASTIC, MSOP-10
文件頁(yè)數(shù)： 6/24頁(yè)
文件大?。?/td> 318K
代理商： LTC3809EMS-1
LTC3809-1
38091f
14
MOSFETs that do not work well at high input voltages (e.g.,
VIN > 5V) may work fine at lower voltages (e.g., 3.3V).
Selecting the N-channel MOSFET is typically easier, since
for a given RDS(ON), the gate charge and turn-on and turn-
off delays are much smaller than for a P-channel MOSFET.
Inductor Value Calculation
Given the desired input and output voltages, the inductor
value and operating frequency, fOSC, directly determine
the inductor’s peak-to-peak ripple current:
I
V
VV
fL
RIPPLE
OUT
IN
OUT
OSC
=
–
Lower ripple current reduces core losses in the inductor,
ESR losses in the output capacitors and output voltage
ripple. Thus, highest efficiency operation is obtained at
low frequency with a small ripple current. Achieving this,
however, requires a large inductor.
A reasonable starting point is to choose a ripple current
that is about 40% of IOUT(MAX). Note that the largest ripple
current occurs at the highest input voltage. To guarantee
that ripple current does not exceed a specified maximum,
the inductor should be chosen according to:
L
VV
fI
V
IN
OUT
OSC
RIPPLE
OUT
IN
≥
–
Burst Mode Operation Considerations
The choice of RDS(ON) and inductor value also determines
the load current at which the LTC3809-1 enters Burst
Mode operation. When bursting, the controller clamps the
peak inductor current to approximately:
I
V
R
BURST PEAK
SENSE MAX
DS ON
()
=
1
4
APPLICATIO S I FOR ATIO
WU
UU
The corresponding average current depends on the amount
of ripple current. Lower inductor values (higher IRIPPLE)
will reduce the load current at which Burst Mode operation
begins.
The ripple current is normally set so that the inductor
current is continuous during the burst periods. Therefore,
IRIPPLE ≤ IBURST(PEAK)
This implies a minimum inductance of:
L
VV
fI
V
MIN
IN
OUT
OSC
BURST PEAK
OUT
IN
≤
–
()
A smaller value than LMIN could be used in the circuit,
although the inductor current will not be continuous
during burst periods, which will result in slightly lower
efficiency. In general, though, it is a good idea to keep
IRIPPLE comparable to IBURST(PEAK).
Inductor Core Selection
Once the value of L is known, the type of inductor must be
selected. Actual core loss is independent of core size for a
fixed inductor value, but is very dependent on the induc-
tance selected. As inductance increases, core losses go
down. Unfortunately, increased inductance requires more
turns of wire and therefore copper losses will increase.
Ferrite designs have very low core losses and are preferred
at high switching frequencies, so design goals can con-
centrate on copper loss and preventing saturation. Ferrite
core material saturates “hard”, which means that induc-
tance collapses abruptly when the peak design current is
exceeded. Core saturation results in an abrupt increase in
inductor ripple current and consequent output voltage
ripple. Do not allow the core to saturate!
相關(guān)PDF資料
PDF描述
LTC3810IG#TR SWITCHING CONTROLLER, PDSO28
LTC3810EG SWITCHING CONTROLLER, PDSO28
LTC3812EFE-5 1 A SWITCHING CONTROLLER, PDSO16
LTC3812IFE-5#TR 1 A SWITCHING CONTROLLER, PDSO16
LTC3812EFE-5#TR 1 A SWITCHING CONTROLLER, PDSO16
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC3809EMSE 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:否 類(lèi)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)
LTC3809EMSE#PBF 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:是 類(lèi)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)
LTC3809EMSE#TR 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:否 類(lèi)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)
LTC3809EMSE#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:是 類(lèi)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)
LTC3809EMSE-1 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:否 類(lèi)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)
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