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发表于 2009-7-15 09:00
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待机模式 不叫(跳周期) 应该是PFM模式,或者你写个skipping,跳周期有点那个意思。没听过啊~~孤陋寡闻了~~
不是FPM,实际61030工作波形,用最小的占空比连续工作10个周期左右,把电容的电充到5.2V左右,然后休眠
直到电容的电又降回5V,然后再触发工作,一般1秒触发一次,所以才能得到惊人的微功耗,uA表都很难测出!
LT和TPS的原始DataSheet都写的是跳周期,或是英文Burst Mode
Burst Mode Operation
The LTC1700 can be enabled to go into Burst Mode
operation at low load currents simply by connecting the
SYNC/MODE pin to a voltage of at least 1.2V. In this mode,
the peak current of the inductor is set as if VITH = 0.36V (at
low duty cycles) even though the voltage at the ITH pin is
actually at a lower value. If the inductor’s average current
is greater than the load requirement, the voltage at the ITH
pin will drop. When the ITH voltage goes below 0.12V, the
internal sleep signal goes low, turning off both external
MOSFETs. Now the load current will solely be supplied by
the output capacitor and the output voltage begins to
droop. This drooping of the output voltage results in the
rise of ITH voltage and once it has risen above 0.22V,
switching will then be resumed on the next oscillator cycle. |
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