IL1084-1.8BT2 查看數據表（PDF） - IK Semicon Co., Ltd
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IL1084-1.8BT2 Datasheet PDF : 15 Pages
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IL1084-xx
When an output capacitor is connected to a regulator and the input is shorted, the output capacitor will discharge into the
output of the regulator. The discharge current depends on the value of the capacitor, the output voltage of the regulator,
and rate of decrease of VIN. In the IL1084 regulator, the internal diode between the output and input pins can withstand
microsecond surge currents of 10A to 20A. With an extremely large output capacitor (≥1000 µf), and with input
instantaneously shorted to ground, the regulator could be damaged. In this case, an external diode is recommended
between the output and input pins to protect the regulator, shown in Figure 5.
FIGURE 5. Regulator with Protection Diode
OVERLOAD RECOVERY
Overload recovery refers to regulator’s ability to recover from a short circuited output. A key factor in the recovery
process is the current limiting used to protect the output from drawing too much power. The current limiting circuit
reduces the output current as the input to output differential increases. Refer to short circuit curve in the curve section.
During normal start-up, the input to output differential is small since the output follows the input. But, if the output is
shorted, then the recovery involves a large input to output differential. Sometimes during this condition the current limiting
circuit is slow in recovering. If the limited current is too low to develop a voltage at the output, the voltage will stabilize at
a lower level. Under these conditions it may be necessary to recycle the power of the regulator in order to get the smaller
differential voltage and thus adequate start up conditions. Refer to curve section for the short circuit current vs. input
differential voltage.
THERMAL CONSIDERATIONS
ICs heats up when in operation, and power consumption is one factor in how hot it gets. The other factor is how well the
heat is dissipated. Heat dissipation is predictable by knowing the thermal resistance between the IC and ambient (θJA).
Thermal resistance has units of temperature per power (C/ W). The higher the thermal resistance, the hotter the IC.
The IL1084 specifies the thermal resistance for each package as junction to case (θJC). In order to get the total
resistance to ambient (θJA), two other thermal resistances must be added, one for case to heat-sink (θCH) and one for
heatsink to ambient (θHA). The junction temperature can be predicted as follows:
TJ is junction temperature, TA is ambient temperature, and PD is the power consumption of the device. Device power
consumption is calculated as follows:
Figure 6 shows the voltages and currents which are present in the circuit.
FIGURE 6. Power Dissipation Diagram
Rev. 04
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