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| 型号： | LTC3838IFE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 22/54页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38TSSOP |
| 标准包装： | 50 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 2MHz |
| 电源电压： | 4.5 V ~ 38 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： | 38-TFSOP （0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 管件 |
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LTC3838
APPLICATIONS INFORMATION
For example, Figure 4a illustrates the voltage waveform
across a 2mΩ sense resistor with a 2010 footprint for a
1.2V/15A converter operating at 100% load. The waveform
is the superposition of a purely resistive component and a
purely inductive component. It was measured using two
scope probes and waveform math to obtain a differential
measurement. Based on additional measurements of the
inductor ripple current 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:
is chosen to be close to the parasitic inductance divided by
the sense resistor (L/R), the resulting waveform looks re-
sistive again, as shown in Figure 4b. For applications using
low V SENSE(MAX) , 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 the equation above to determine the ESL.
However, do not over filter. Keep the RC time constant less
than or equal to the inductor time constant to maintain a
V ESL(STEP) t ON ? t OFF
Δ I L
t ON + t OFF
ESL=
?
high enough ripple voltage on V RSENSE .
Note that the SENSE1 – and SENSE2 – pins are also used
for sensing the output voltage for the adjustment of top
where V ESL(STEP) is the voltage step caused by the ESL
and shown in Figure 4a, and t ON and t OFF are top MOSFET
on-time and off-time respectively. If the RC time constant
gate on time, t ON . For this purpose, there is an additional
internal 500k resistor from each SENSE – pin to SGND,
therefore there is an impedance mismatch with their cor-
responding SENSE + pins. The voltage drop across the
R F causes an offset in sense voltage. For example, with
R F = 100Ω, at V OUT = V SENSE– = 5V, the sense-voltage
offset V SENSE(OFFSET) = V SENSE– ? R F /500k = 1mV. Such
V SENSE
20mV/DIV
500ns/DIV
3838 F04a
V ESL(STEP)
small offset may seem harmless for current limit, but
could be significant for current reversal detection (I REV ),
causing excess negative inductor current at discontinuous
mode. Also, at V SENSE(MAX) = 30mV, a mere 1mV offset
will cause a significant shift of zero-current ITH voltage
by (2.4V – 0.8V) ? 1mV/30mV = 53mV. Too much shift
Figure 4a. Voltage Waveform Measured
Directly Across the Sense Resistor
V SENSE
20mV/DIV
may not allow the output voltage to return to its regulated
value after the output is shorted due to ITH foldback.
Therefore, when a larger filter resistor R F value is used,
it is recommended to use an external 500k resistor from
each SENSE + pin to SGND, to balance the internal 500k
resistor at its corresponding SENSE – pin.
The previous discussion generally applies to high density/
high current applications where I OUT(MAX) > 10A and low
inductor values are used. For applications where I OUT(MAX)
500ns/DIV
3838 F04b
Figure 4b. Voltage Waveform Measured After the
Sense Resistor Filter. C F = 1000pF, R F = 100Ω
3838fa
22
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相关代理商/技术参数 |
参数描述 |
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| LTC3838IUHF#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) |
| LTC3838IUHF#TRPBF | 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) |
| LTC3838IUHF-1#PBF | 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM CM 38QFN 制造商:Linear Technology 功能描述:BUCK DUAL CNTRL 4.5-38V 2MHZ 38QFN 制造商:Linear Technology 功能描述:BUCK, DUAL, CNTRL, 4.5-38V, 2MHZ, 38QFN 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Dual, Fast, Accurate Step-Down Controller with Differential 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, DUAL, BUCK, ADJ, QFN-38, Primary Input Voltage:38V, No. of Outputs:2, Output Current:25A, No. of Pins:38, Operating Temperature Min:-40C, Operating Temperature Max:125C, MSL:MSL 1 - Unlimited , RoHS Compliant: Yes |
| LTC3838IUHF-1#TRPBF | 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM CM 38QFN 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Dual, Fast, Accurate Step-Down Controller with Differential 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, DUAL, BUCK, ADJ, QFN-38, Primary Input Voltage:38V, No. of Outputs:2, Output Current:25A, No. of Pins:38, Operating Temperature Min:-40C, Operating Temperature Max:125C, MSL:MSL 1 - Unlimited , RoHS Compliant: Yes |
| LTC3838IUHF-2#PBF | 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM CM 38-QFN 制造商:Linear Technology 功能描述:BUCK DUAL CNTRL 4.5-38V 2MHZ 38QFN 制造商:Linear Technology 功能描述:DC-DC CONTROLLER BUCK 2MHZ QFN-38 制造商:Linear Technology 功能描述:BUCK, DUAL, CNTRL, 4.5-38V, 2MHZ, 38QFN 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Dual, Fast, Accurate Step-Down Controller with Differential |
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