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| 型号： | TPS40222DRPTG4 |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | 3.5 A SWITCHING REGULATOR, 1500 kHz SWITCHING FREQ-MAX, PDSO6 |
| 封装： | 3 X 3 MM, GREEN, PLASTIC, VSON-6 |
| 文件页数： | 27/27页 |
| 文件大小： | 662K |
| 代理商： | TPS40222DRPTG4 |
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Soft-Start
V
REF
t
SS
+
0.8 V
550 ms
(1)
V
OUT
t
SS
+
1.2 V
550 ms
(2)
Output Short-Circuit Protection
Bootstrap
SLUS642A – OCTOBER 2005 – REVISED JANUARY 2006
DETAILED DESCRIPTION (continued)
During power-on, the TPS40222 slowly increases the voltage to the non-inverting input to the error amplifier. In
this way, the TPS40222 slowly ramps up the output voltage until the voltage on the non-inverting input to the
error amplifier reaches 0.8 V. At that time, the voltage at the non-inverting input to the error amplifier remains at
0.8 V.
Upon startup, the time for the voltage on the non-inverting input of the error amplifier to reach 0.8 V is
approximately 550 s. The rate of rise of the voltage on the output of a TPS40222 is determined by the resistive
divider network that sets the converter output voltage.
For example, the rate of rise of the internal soft-start is:
where
t
SS in the example is the typical soft-start time of 550 s
For a 1.2-V output converter, the rate of rise observed at the output is:
Current fault (short-circuit) protection is provided by sensing the current through the switching MOSFET while it is
in the ON state and comparing with a preset internal level. If the current exceeds this level, the switching pulse
width is limited causing the output voltage to decay. As the output voltage decays, the operating frequency is
also decreased, thereby reducing power dissipation.
If the fault condition persists, and the output voltage continues to decay, then a watchdog circuit discharges the
internal soft-start capacitor, effectively shutting off the converter. When this interval is completed, the converter
then attempts to restart.
To drive the internal N-channel MOSFET, a bootstrap, or boost circuit, is added to provide a voltage source
higher than the input voltage of sufficient energy to fully enhance the MOSFET each switching cycle. During the
freewheeling portion of the switching cycle (refer to Figure 9), the internal MOSFET is off, and the voltage at the
SW node is clamped to just below ground by D1. At this time the input voltage (less the drop of the internal
BOOST diode) is impressed upon C2, allowing it to charge. When the internal MOSFET is commanded to turn
ON, the SW node rises towards VIN, and the voltage on the BOOST pin rises to approximately 2 × VIN. This
voltage is used to further turn on the internal MOSFET for the remainder of the switching cycle.
9
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相关代理商/技术参数 |
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|---|---|
| TPS40222EVM-001 | 功能描述:电源管理IC开发工具 Non-Sync Buck Conv Eval Mod RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
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| TPS40-24 | 制造商:TOTAL-POWER 制造商全称:TOTAL-POWER 功能描述:40 WATT OPEN - FRAME SWITCHING POWER SUPPLY |
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| TPS40-30 | 制造商:TOTAL-POWER 制造商全称:TOTAL-POWER 功能描述:40 WATT OPEN - FRAME SWITCHING POWER SUPPLY |
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