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參數(shù)資料
| 型號(hào)： | LTC3728LIUH-1#TR |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3 A DUAL SWITCHING CONTROLLER, 590 kHz SWITCHING FREQ-MAX, PQCC32 |
| 封裝： | 5 X 5 MM, PLASTIC, MO-220WHHD, QFN-32 |
| 文件頁數(shù)： | 6/32頁 |
| 文件大?。?/td> | 475K |
| 代理商： | LTC3728LIUH-1#TR |
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LTC3728L-1
14
3728l1fc
APPLICATIONS INFORMATION
25% of the current limit determined by RSENSE. Lower
inductor values (higher ΔIL) will cause this to occur at
lower load currents, which can cause a dip in efciency in
the upper range of low current operation. In Burst Mode
operation, lower inductance values will cause the burst
frequency to decrease.
Inductor Core Selection
Usually, high inductance is preferred for small current
ripple and low core loss. Unfortunately, increased induc-
tance requires more turns of wire or a smaller air gap in
the inductor core, resulting in high copper loss or low
saturation current. Once the value of L is known, the actual
inductor must be selected. There are two popular types
of core material of commercial available inductors. Ferrite
core inductors usually have very low core loss and are
preferred at high switching frequencies, so design goals
can concentrate on copper loss and preventing satura-
tion. However, ferrite core saturates “hard”, which means
that inductance collapses abruptly when the peak design
current is exceeded. This results in an abrupt increase in
inductor ripple current and consequent output voltage
ripple. One advantage of the LTC3728L-1 is its current
mode control that detects and limits cycle-by-cycle peak
inductor current. Therefore, accurate and fast protection
is achieved if the inductor is saturated in steady state or
during transient mode.
Powdered iron core inductors usually saturate “soft”, which
means the inductance drops in a linear fashion when the
current increases. However, the core loss of the powder
iron inductor is usually higher than the ferrite inductor.
So designs with high switching frequency should also
address inductor core loss.
Inductor manufacturers usually provide inductance, DCR,
(peak) saturation current and (DC) heating current ratings
in the inductor data sheet. A good supply design should
not exceed the saturation and heating current rating of
the inductor.
Power MOSFET and D1 Selection
Two external power MOSFETs must be selected for each
controller in the LTC3728L-1: One N-channel MOSFET for
the top (main) switch, and one N-channel MOSFET for the
bottom (synchronous) switch.
The peak-to-peak drive levels are set by the INTVCC
voltage. This voltage is typically 5V during start-up
(see EXTVCC Pin Connection). Consequently, logic-level
threshold MOSFETs must be used in most applications.
The only exception is if low input voltage is expected (VIN
< 5V); then, sub-logic level threshold MOSFETs (VGS(TH)
< 3V) should be used. Pay close attention to the BVDSS
specication for the MOSFETs as well; most of the logic
level MOSFETs are limited to 30V or less.
Selection criteria for the power MOSFETs include the “ON”
resistance RDS(ON), Miller capacitance CMILLER, input
voltage and maximum output current. Miller capacitance,
CMILLER, can be approximated from the gate charge curve
usually provided on the MOSFET manufacturers’ data
sheet. CMILLER is equal to the increase in gate charge
along the horizontal axis while the curve is approximately
at divided by the specied change in VDS. This result is
then multiplied by the ratio of the application applied VDS
to the Gate charge curve specied VDS. When the IC is
operating in continuous mode the duty cycles for the top
and bottom MOSFETs are given by:
Main Switch Duty Cycle
=
VOUT
VIN
Synchronous Switch Duty Cycle
=
VIN –VOUT
VIN
The MOSFET power dissipations at maximum output
current are given by:
PMAIN =
VOUT
VIN
IMAX
()2 1+
()R
DS(ON) +
VIN
()2 IMAX
2
RDR
() C
MILLER
()
1
VINTVCC –VTHMIN
+
1
VTHMIN
f
()
PSYNC =
VIN –VOUT
VIN
IMAX
()2 1+
()R
DS(ON)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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| LTC3728LXCUH | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3728LXCUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 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 升壓:是 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 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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