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参数资料
| 型号： | L7980TR |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | 3.5 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | 3 X 3 MM, 1.08 MM HEIGHT, ROHS COMPLIANT, VFQFPN-8 |
| 文件页数： | 5/44页 |
| 文件大小： | 1247K |
| 代理商： | L7980TR |
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L7980
Functional description
Doc ID 15181 Rev 3
13/44
5.4
Overcurrent protection
The L7980 implements the overcurrent protection sensing current flowing through the power
MOSFET. Due to the noise created by the switching activity of the power MOSFET, the
current sensing is disabled during the initial phase of the conduction time. This avoids an
erroneous detection of a fault condition. This interval is generally known as “masking time”
or “blanking time”. The masking time is about 200 ns.
When the overcurrent is detected, two different behaviors are possible depending on the
operating condition.
1.
Output voltage in regulation. When the overcurrent is sensed, the power MOSFET is
switched off and the internal reference (VREF), that biases the non-inverting input of the
error amplifier, is set to zero and kept in this condition for a soft start time (TSS, 2048
clock cycles). After this time, a new soft start phase takes place and the internal
reference begins ramping (see Figure 8.a).
2.
Soft start phase. If the overcurrent limit is reached the power MOSFET is turned off
implementing the pulse by pulse overcurrent protection. During the soft start phase,
under overcurrent condition, the device can skip pulses in order to keep the output
current constant and equal to the current limit. If at the end of the “masking time” the
current is higher than the overcurrent threshold, the power MOSFET is turned off and it
will skip one pulse. If, at the next switching on at the end of the “masking time” the
current is still higher than the threshold, the device will skip two pulses. This
mechanism is repeated and the device can skip up to seven pulses. While, if at the end
of the “masking time” the current is lower than the overcurrent threshold, the number of
skipped cycles is decreased of one unit. At the end of soft start phase the output
voltage is in regulation and if the overcurrent persists the behavior explained above
takes place. (see Figure 8.b)
So the overcurrent protection can be summarized as an “hiccup” intervention when the
output is in regulation and a constant current during the soft start phase. If the output is
shorted to ground when the output voltage is on regulation, the overcurrent is triggered and
the device starts cycling with a period of 2048 clock cycles between “hiccup” (power
MOSFET off and no current to the load) and “constant current” with very short on-time and
with reduced switching frequency (up to one eighth of normal switching frequency). See
Figure 32. for short circuit behavior.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| L7981 | 功能描述:直流/直流开关调节器 3A Step-Down Reg 3A DC 4.5-28V 250Khz RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| L7981A | 制造商:STMicroelectronics 功能描述:POWER CONVERSION - Rail/Tube 制造商:STMicroelectronics 功能描述:3A Step-Down Reg 3.7A 4.5 to 28V 1MHz 制造商:ST 功能描述:3A STEP-DOWN SWITCHING REGULATOR |
| L7981ATR | 功能描述:直流/直流开关调节器 3 A Step-Down Reg 4.5V to 28V 250 kHz RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| L7981ATR/BLK | 制造商:STMicroelectronics 功能描述:3 A STEP-DOWN SWITCHING REGULATO - Tape and Reel 制造商:STMicroelectronics 功能描述:STMicroelectronics L7981ATR/BLK Interface Misc |
| L7981TR | 功能描述:直流/直流开关调节器 3A DC 4.5 V to 28 V Adj 0.6V 250 kHz RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
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