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| 型号： | LTC3876EFE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 19/48页 |
| 文件大小： | 0K |
| 描述： | IC CTLR DC/DC DDR DUAL 38-TSSOP |
| 产品培训模块： | LTC3876 Dual DC/DC Controller |
| 标准包装： | 50 |
| 应用： | 控制器，DDR，DDR2，DDR3 |
| 输入电压： | 4.5 V ~ 38 V |
| 输出数： | 2 |
| 输出电压： | 可调 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 38-TFSOP （0.173"，4.40mm 宽）裸露焊盘 |
| 供应商设备封装： | 38-TSSOP 裸露焊盘 |
| 包装： | 管件 |
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LTC3876
APPLICATIONS INFORMATION
–
C IN
+
V IN
LTC3876
M T
L
POWER TRACE
PARASITICS
V OUTSENSE1+ V OUTSENSE1–
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
3876 F02
Figure 2. Differential Output Sensing Used to Correct Line Loss Variations
in a High Power Distributed System with a Shared Ground Plane
R T [k Ω] =
f ( kHz )
Δ I L = ? OUT ? ? 1– OUT ?
? ? ? V OUT ?
L = ?
? ? 1–
?
Switching Frequency Programming
The choice of operating frequency is a trade-off between
efficiency and component size. Lowering the operating fre-
quency improves efficiency by reducing MOSFET switching
losses but requires larger inductance and/or capacitance
to maintain low output ripple voltage. Conversely, raising
the operating frequency degrades efficiency but reduces
component size.
The switching frequency of the LTC3876 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:
41550
– 2.2
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-
related in that higher operating frequencies allow the use of
smaller inductor and capacitor values. A higher frequency
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 :
? V ? ? V ?
? f ?L ? ? V IN ?
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:
V OUT
? f ? Δ I L(MAX) ? ? V IN(MAX) ?
3876f
19
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| LTC3876IFE#PBF | 功能描述:IC CTLR DC/DC DDR DUAL 38-TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
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