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參數(shù)資料
| 型號： | LP3971SQ-B410 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 電源管理 |
| 英文描述： | POWER MANAGEMENT UNIT FOR ADVANCED APPLICATION PROCESSORS |
| 中文描述： | 3-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC40 |
| 封裝： | 5 X 5 MM, LLP-40 |
| 文件頁數(shù)： | 15/42頁 |
| 文件大小： | 1350K |
| 代理商： | LP3971SQ-B410 |
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Buck Converter Operation
(Continued)
During PFM operation, the converter positions the output
voltage slightly higher than the nominal output voltage during
PWM operation, allowing additional headroom for voltage
drop during a load transient from light to heavy load. The
PFM comparators sense the output voltage via the feedback
pin and control the switching of the output FETs such that the
output voltage ramps between
<
0.6% and
<
1.7% above the
nominal PWM output voltage. If the output voltage is below
the “high” PFM comparator threshold, the PMOS power
switch is turned on. It remains on until the output voltage
reaches the ‘high’ PFM threshold or the peak current ex-
ceeds the IPFM level set for PFM mode. The typical peak
current in PFM mode is: I
= 112 mA + V
/27
. Once the
PMOS power switch is turned off, the NMOS power switch is
turned on until the inductor current ramps to zero. When the
NMOS zero-current condition is detected, the NMOS power
switch is turned off. If the output voltage is below the ‘high’
PFM comparator threshold (see
Figure 5
), the PMOS switch
is again turned on and the cycle is repeated until the output
reaches the desired level. Once the output reaches the ‘high’
PFM threshold, the NMOS switch is turned on briefly to ramp
the inductor current to zero and then both output switches
are turned off and the part enters an extremely low power
mode. Quiescent supply current during this ‘sleep’ mode is
16 μA(typ), which allows the part to achieve high efficiencies
under extremely light load conditions. When the output drops
below the ‘low’ PFM threshold, the cycle repeats to restore
the output voltage (average voltage in PFM mode) to
<
1.15% above the nominal PWM output voltage. If the load
current should increase during PFM mode (see
Figure 5
)
causing the output voltage to fall below the ‘low2’ PFM
threshold, the part will automatically transition into fixed-
frequency PWM mode. Typically when V
= 3.6V the part
transitions from PWM to PFM mode at 100 mA output
current.
20180712
FIGURE 4. Typical PFM Operation
20180713
FIGURE 5. Operation in PFM Mode and Transfer to PWM Mode
L
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP3971SQ-B410/NOPB | 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| LP3971SQ-B410EV | 功能描述:電源管理IC開發(fā)工具 LP3971SQ-B410 EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| LP3971SQ-B510/NOPB | 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| LP3971SQ-C818/NOPB | 制造商:Texas Instruments 功能描述: |
| LP3971SQ-D510 | 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
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