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參數(shù)資料
| 型號： | LM2696MXAX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3A, Constant On Time Buck Regulator |
| 中文描述： | 6.4 A SWITCHING REGULATOR, 500 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | TSSOP-16 |
| 文件頁數(shù)： | 12/19頁 |
| 文件大?。?/td> | 833K |
| 代理商： | LM2696MXAX |
Application Information
(Continued)
UNDER- & OVER-VOLTAGE CONDITIONS
The LM2696 has a built in under-voltage comparator that
controls PGOOD. Whenever the output voltage drops below
the set threshold, the PGOOD open drain FET will turn on
pulling the pin to ground. For an over-voltage event, there is
no separate comparator to control PGOOD. However, the
loop responds to prevent this event from occurring because
the error comparator is essentially sensing an OVP event. If
the output is above the feedback threshold then the part will
not switch back on; therefore, the worst-case condition is
one on-time pulse.
CURRENT LIMIT
The LM2696 utilizes a peak-detect current limit that senses
the current through the FET when conducting and will imme-
diately terminate the on-pulse whenever the peak current
exceeds the threshold (4.9A typical). In addition to terminat-
ing the present on-pulse, it enforces a mandatory off-time
that is related to the feedback voltage.
If current limit trips and the feedback voltage is close to its
nominal value of 1.25V, the off-time imposed will be relatively
short. This is to prevent the output from dropping or any fold
back from occurring if a momentary short occurred because
of a transient or load glitch. If a short circuit were present, the
off-time would extend to approximately 12 μs. This ensures
that the inductor current will reach a low value (approxi-
mately 0A) before the next switching cycle occurs. The
extended off-time prevents runaway conditions caused by
hard shorts and high side blanking times.
If the part is in an over current condition, the output voltage
will begin to drop as shown in
Figure 4
. If the output voltage
is dropping and the current is below the current limit thresh-
old, (I
), the part will assert a pulse (t
) after a minimum
off-time (t
1
). This is in an attempt to raise the output voltage.
If the part is in an over current condition and the output
voltage is below the regulation value (V
) as shown in
Figure
4
, the part will assert a pulse of minimal width (t
) and extend
the off-time (t
). In the event that the voltage is below the
regulation value (V
) and the current is below the current
limit value, the part will assert two (or more) pulses sepa-
rated by some minimal off-time (t
1
).
20153437
FIGURE 3. Startup Timing Diagram
L
www.national.com
12
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2696MXAX/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2698EVAL | 功能描述:電源管理IC開發(fā)工具 EVAL BOARDFOR LM2698 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 |
| LM2698MM-ADJ | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2698MM-ADJ/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 1.35A BOOST REG RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2698MM-ADJ/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Converter (DC-DC) / Switching Regu |
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