参数资料
型号: LTC3839EUH#PBF
厂商: Linear Technology
文件页数: 17/50页
文件大小: 0K
描述: IC REG CTRLR BUCK PWM CM 32-QFN
标准包装: 73
系列: PolyPhase®
PWM 型: 电流模式
输出数: 1
频率 - 最大: 2MHz
电源电压: 4.5 V ~ 38 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: -40°C ~ 125°C
封装/外壳: 32-WFQFN 裸露焊盘
包装: 管件
LTC3839
APPLICATIONS INFORMATION
C IN
+
V IN
LTC3839
M T
L
POWER TRACE
PARASITICS
V OUTSENSE+ V OUTSENSE–
R FB2 R FB1
M B
C OUT1
±V DROP(PWR)
I LOAD
C OUT2 I
LOAD
GROUND TRACE
PARASITICS
±V DROP(GND)
OTHER CURRENTS
FLOWING IN
SHARED GROUND
PLANE
3839 F02
Figure 2. Differential Output Sensing Used to Correct Line Loss Variations
in a High Power Distributed System with a Shared Ground Plane
to maintain low output ripple voltage. Conversely, raising
the operating frequency degrades efficiency but reduces
component size.
The switching frequency of the LTC3839 can be pro-
grammed from 200kHz to 2MHz by connecting a resistor
from the RT pin to signal ground. The value of this resistor
can be chosen according to the following formula:
generally results in lower efficiency because 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 ? I L decreases with higher
inductance or frequency and increases with higher V IN :
Δ I L = ? OUT ? ? 1– OUT ?
R T [ kΩ ] =
41550
f [ kHz ]
– 2.2
? V ? ? V ?
? f ?L ? ? V IN ?
? ? ? V OUT ?
L = ?
V OUT
? ?
?
? f ? Δ I L(MAX) ? ?
The overall controller system, including the clock PLL
and switching channels, has a synchronization range of
no less than ±30% around this programmed frequency.
Therefore, during external clock synchronization be sure
that the external clock frequency is within this ±30% range
of the RT programmed frequency. It is advisable that the
RT programmed frequency be equal the external clock for
maximum synchronization margin. Refer to the “Phase
and Frequency Synchronization” section for more details.
Inductor Value Calculation
The operating frequency and inductor selection are inter-
Accepting larger values of ? I L allows the use of low induc-
tances, but results in higher output voltage ripple, higher
ESR losses in the output capacitor, and greater core losses.
A reasonable starting point for setting ripple current is ? I L
= 0.4 ? I MAX . The maximum ? I L occurs at the maximum
input voltage. To guarantee that ripple current does not
exceed a specified maximum, the inductance should be
chosen according to:
1–
V IN(MAX) ?
related in that higher operating frequencies allow the use of
smaller inductor and capacitor values. A higher frequency
3839fa
17
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LTC3839IUH#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 32-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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LTC3850EGN#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP 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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