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参数资料
| 型号： | LTC3828EUH#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 32-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 590kHz |
| 占空比： | 99.4% |
| 电源电压： | 4.5 V ~ 28 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 ~ 85°C |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3828
APPLICATIONS INFORMATION
of MOSFET gate charge losses. In addition to this basic
trade-off, the effect of inductor value on ripple current and
low current operation must also be considered.
The inductor value has a direct effect on ripple current.
The inductor ripple current Δ I L decreases with higher
inductance or frequency and increases with higher V IN :
is achieved if the inductor is saturated in steady state or
during transient mode.
Powder iron 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
V OUT ? 1 – OUT ?
Δ I L =
1
( f )( L )
? V ?
? V IN ?
design with high switching frequency should pay attention
to the inductor core loss too.
Inductor manufacturers usually provide inductance, DCR,
Accepting larger values of Δ I L allows the use of low
inductances, but results in higher output voltage ripple
and greater core losses. A reasonable starting point for
setting ripple current is Δ I L = 0.3(I MAX ). The maximum
Δ I L occurs at the maximum input voltage.
The inductor value also has secondary effects. The tran-
sition to Burst Mode operation begins when the average
inductor current required results in a peak current below
25% of the current limit determined by R SENSE . Lower
inductor values (higher Δ I L ) will cause this to occur at
lower load currents, which can cause a dip in ef?ciency in
the upper range of low current operation. In Burst Mode
operation, lower inductance values will cause the burst
frequency to decrease.
Inductor Selection
Usually, high inductance is preferred for small current
ripple and low core loss. Unfortunately, increased induc-
tance requires more turns of wire or small air gap of the
inductor, 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
saturation. However, ferrite core saturates “hard”, which
means that inductance collapses abruptly when the peak
design current is exceeded. This results in an abrupt in-
crease in inductor ripple current and consequent output
(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 LTC3828: 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 INTV CC voltage.
This voltage is typically 5V during start-up. Consequently,
logic-level threshold MOSFETs must be used in most ap-
plications. The only exception is if low input voltage is ex-
pected (V IN < 5V); then, sub-logic level threshold MOSFETs
(V GS(TH) < 3V) should be used. Pay close attention to the
BV DSS speci?cation 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, R DS(ON) , Miller capacitance, C MILLER , input
voltage and maximum output current. Miller capacitance,
C MILLER , can be approximated from the gate charge curve
usually provided on the MOSFET manufacturers’ data
sheet. C MILLER is equal to the increase in gate charge
along the horizontal axis while the curve is approximately
?at divided by the speci?ed change in V DS . This result is
then multiplied by the ratio of the application applied V DS
to the Gate charge curve speci?ed V DS . When the IC is
operating in continuous mode the duty cycles for the top
and bottom MOSFETs are given by:
voltage ripple. One advantage of the LTC3828 is its current
mode control that detects and limits cycle-by-cycle peak
inductor current. Therefore, accurate and fast protection
Main Switch Duty Cycle =
V OUT
V IN
3828fc
16
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| LTC3829EFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
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| LTC3829EUHF#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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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