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参数资料
| 型号： | LM21215MHX |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 23.5 A SWITCHING REGULATOR, 525 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封装： | TSSOP-20 |
| 文件页数： | 3/24页 |
| 文件大小： | 512K |
| 代理商： | LM21215MHX |
SHORT-CIRCUIT PROTECTION
In the unfortunate event that the output is shorted with a low
impedance to ground, the LM21215 will limit the current into
the short by resetting the device. A short-circuit condition is
sensed by a current-limit condition coinciding with a voltage
on the FB pin that is lower than 100 mV. When this condition
occurs, the device will begin its reset sequence, turning off
both power FETs and discharging the soft-start capacitor after
t
RESETSS (nominally 110 s). The device will then attempt to
restart. If the short-circuit condition still exists, it will reset
again, and repeat until the short-circuit is cleared. The reset
prevents excess current flowing through the FETs in a highly
inefficient manner, potentially causing thermal damage to the
device or the bus supply.
30103719
FIGURE 1. Current Limit Conditions
THERMAL PROTECTION
Internal thermal shutdown circuitry is provided to protect the
integrated circuit in the event that the maximum junction tem-
perature is exceeded. When activated, typically at 165°C, the
LM21215 tri-states the power FETs and resets soft start. After
the junction cools to approximately 155°C, the device starts
up using the normal start up routine. This feature is provided
to prevent catastrophic failures from accidental device over-
heating. Note that thermal limit will not stop the die from
operating above the specified maximum operating tempera-
ture,125°C. The die should be kept under 125°C to guarantee
correct operation.
POWER GOOD FLAG
The PGOOD pin provides the user with a way to monitor the
status of the LM21215. In order to use the PGOOD pin, the
application must provide a pull-up resistor to a desired DC
voltage (i.e. Vin). PGOOD will respond to a fault condition by
pulling the PGOOD pin low with the open-drain output.
PGOOD will pull low on the following conditions: 1) V
FB moves
above or below the V
OVP or VUVP, respectively 2) The enable
pin (EN) is brought below the enable threshold 3) The device
enters a pre-biased output condition (V
FB>VSS).
Figure 2 shows the conditions that will cause PGOOD to fall.
11
www.national.com
LM21215
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM21215MHX/NOPB | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LM212B | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Optoelectronic |
| LM212D | 制造商:TI 制造商全称:Texas Instruments 功能描述:OPERATIONAL AMPLIFIERS/BUFFERS |
| LM212H | 制造商:Motorola Inc 功能描述: |
| LM212JG | 制造商:TI 制造商全称:Texas Instruments 功能描述:OPERATIONAL AMPLIFIERS/BUFFERS |
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