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参数资料
| 型号： | LTC3891EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 20TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 835kHz |
| 占空比： | 99% |
| 电源电压： | 4 V ~ 60 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： | 20-TSSOP（0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3891
APPLICATIONS INFORMATION
R SENSE =
I MAX +
R SENSE(EQUIV) =
I MAX +
R D =
LowValueResistorCurrentSensing
A typical sensing circuit using a discrete resistor is shown
in Figure 2a. R SENSE is chosen based on the required
output current.
The current comparator has a maximum threshold
V SENSE(MAX) determined by the I LIM setting. The current
comparator threshold voltage sets the peak of the induc-
tor current, yielding a maximum average output current,
I MAX , equal to the peak value less half the peak-to-peak
ripple current, ?I L . To calculate the sense resistor value,
use the equation:
V SENSE(MAX)
D I L
2
To ensure that the application will deliver full load current
over the full operating temperature range, choose the
minimum value for the Maximum Current Sense Threshold
(V SENSE(MAX) ) in the Electrical Characteristics table (30mV,
50mV or 75mV, depending on the state of the I LIM pin).
When using the controller in very low dropout conditions,
the maximum output current level will be reduced due
to the internal compensation required to meet stability
criterion for buck regulators operating at greater than
50% duty factor. A curve is provided in the Typical Perfor-
mance Characteristics section to estimate this reduction
in peak inductor current depending upon the operating
duty factor.
Inductor DCR Sensing
For applications requiring the highest possible efficiency
at high load currents, the LTC3891 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 resistance of the copper wire, which can be
less than 1mΩ for today’s low value, high current inductors.
In a high current application requiring such an inductor,
power loss through a sense resistor would cost several
points of efficiency compared to inductor DCR sensing.
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
the inductor DCR multiplied by R2/(R1 + R2). R2 scales the
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 Inductor
Value Calculation section, the target sense resistor
value is:
V SENSE(MAX)
D I L
2
To ensure that the application will deliver full load current
over the full operating temperature range, choose the
minimum value for the Maximum Current Sense Threshold
(V SENSE(MAX) ) in the Electrical Characteristics table (30mV,
50mV or 75mV, depending on the state of the I LIM pin).
Next, determine the DCR of the inductor. When provided,
use the manufacturer’s maximum value, usually given at
20°C. Increase this value to account for the temperature
coefficient of copper resistance, which is approximately
0.4%/°C. A conservative value for T L(MAX) is 100°C.
To scale the maximum inductor DCR to the desired sense
resistor value (R D ), use the divider ratio:
R SENSE(EQUIV)
DCR MAX at T L(MAX)
C1 is usually selected to be in the range of 0.1μF to 0.47μF.
This forces R1 || R2 to around 2k, reducing error that might
have been caused by the SENSE + pin’s ±1μA current.
3891fa
15
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| LTC3891EUDC#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 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 |
| LTC3891EUDC#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 900kHz QFN20 |
| LTC3891EUDC#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 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) |
| LTC3891HFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 20TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 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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