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参数资料
| 型号： | LTC3829EUHF#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, PQCC38 |
| 封装： | 5 X 7 MM, LEAD FREE, PLASTIC, M0-220WHKD, QFN-38 |
| 文件页数： | 9/40页 |
| 文件大小： | 478K |
| 代理商： | LTC3829EUHF#PBF |
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LTC3829
3829f
applicaTions inForMaTion
and the on-time and off-time of the top switch, the value
of the parasitic inductance was determined to be 0.5nH
using the equation:
ESL
V
I
t
ESL STEP
L
ON
OFF
ON
OFF
=
+
(
)
(1)
If the RC time constant is chosen to be close to the
parasitic inductance divided by the sense resistor (L/R),
the resulting waveform looks resistive again, as shown
in Figure 4. For applications using low maximum sense
voltages, check the sense resistor manufacturer’s data
sheet for information about parasitic inductance. In the
absence of data, measure the voltage drop directly across
the sense resistor to extract the magnitude of the ESL step
and use Equation 1 to determine the ESL. However, do not
overfilter. Keep the RC time constant, less than or equal
to the inductor time constant to maintain a high enough
ripple voltage of
VSENSE. The above generally applies to
high density/high current applications where IMAX > 10A
and low values of inductors are used. For applications
500ns/DIV
VSENSE
20mV/DIV
3829 F03
VESL(STEP)
Figure 3. Voltage Waveform Measured
Directly Across the Sense Resistor
500ns/DIV
VSENSE
20mV/DIV
3829 F04
Figure 4. Voltage Waveform Measured After
the Sense Resistor Filter. CF = 1000pF, RF = 100Ω
where IMAX < 10A, set RF to 10Ω and CF to 1000pF. This
will provide a good starting point. The filter components
need to be placed close to the IC. The positive and nega-
tive sense traces need to be routed as a differential pair
and Kelvin connected to the sense resistor.
Inductor DCR Sensing
For applications requiring the highest possible efficiency
at high load currents, the LTC3829 is capable of sensing
the voltage drop across the inductor DCR, as shown in
Figure 2b. The DCR of the inductor represents the small
amount of DC winding resistance of the copper, which
can be less than 1mΩ for today’s low value, high current
inductors. In a high current application requiring such an
inductor, conduction loss through a sense resistor would
costseveralpointsofefficiencycomparedtoDCRsensing.
If the external R1|| R2 C1 time constant is chosen to be
exactly equal to the L/DCR time constant, the voltage drop
across the external capacitor is equal to the drop across
theinductorDCRmultipliedbyR2/(R1+R2).R2scalesthe
voltage across the sense terminals for applications where
the DCR is greater than the target sense resistor value.
To properly dimension the external filter components, the
DCR of the inductor must be known. It can be measured
using a good RLC meter, but the DCR tolerance is not
always the same and varies with temperature; consult the
manufacturers’ data sheets for detailed information.
Using the inductor ripple current value from the Induc-
tor Value Calculation section, the target sense resistor
value is:
R
V
I
SENSE EQUIV
SENSE MAX
MAX
L
(
)
(
)
=
+
2
To ensure that the application will deliver full load current
over the full operating temperature range, choose the
minimumvaluefortheMaximumCurrentSenseThreshold
(VSENSE(MAX))intheElectricalCharacteristicstable(25mV,
45mV or 68mV, depending on the state of the ILIM pin).
Next, determine the DCR of the inductor. Where provided,
use the manufacturer’s maximum value, usually given at
20°C. Increase this value to account for the temperature
coefficient of resistance, which is approximately 0.4%/°C.
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相关代理商/技术参数 |
参数描述 |
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| LTC3829IFE#TRPBF | 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® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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