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ILE4271-2 Datasheet(PDF) 2 Page - IK Semicon Co., Ltd |
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ILE4271-2 Datasheet(HTML) 2 Page - IK Semicon Co., Ltd |
2 / 9 page ILE4271-2 January, 2011, Rev. 01 Application Description The IC regulates an input voltage in the range of 5.5 V < VI < 36 V to VQnom = 5.0 V. Up to 26 V it produces a regulated output current of more than 550 mA. Above 26 V the save- operating-area protection allows operation up to 36 V with a regulated output current of more than 300 mA. Overvoltage protection limits operation at 42 V. The overvoltage protection hysteresis restores operation if the input voltage has dropped below 36 V. The IC can be switched off via the inhibit input, which causes the quiescent current to drop below 50 uA. A reset signal is generated for an output voltage of VQ < 4.5 V. The watchdog circuit monitors a connected controller. If there is no positive-going edge at the watchdog input within a fixed time, the reset output is set to low. The delay for power-on reset and the maximum permitted watchdog-pulse period can be set externally with a capacitor. Design Notes for External Components An input capacitor CI is necessary for compensation of line influences. The resonant circuit consisting of lead inductance and input capacitance can be damped by a resistor of approx. 1 Ohm in series with CI. An output capacitor CQ is necessary for the stability of the regulating circuit. Stability is guaranteed at values of CQ ≤22 uF and an ESR of <3 Ohm. Circuit Description The control amplifier compares a reference voltage, which is kept highly accurate by resistance adjustment, to a voltage that is proportional to the output voltage and drives the base of a series transistor via a buffer. Saturation control as a function of the load current prevents any over-saturation of the power element. If the output voltage decreases below 4.5 V, an external capacitor CD on pin 4 (D) will be discharged by the reset generator. If the voltage on this capacitor VD drops below VDRL, a reset signal is generated on pin 2 (RO), i.e. reset output is set low. If the output voltage rises above 4.5 V, CD will be charged with constant current. After the power-on-reset time VD reaches VDU and the reset output will be set high again. The value of the power- on-reset time can be set within a wide range depending on the capacity of CD. The value of the pull-up resistor at reset output is typically 30 kOhm. After VD has reached the voltage VDU and reset was set to high, the watchdog circuit is enabled and discharges CD with a constant current. If there is no positive-going edge observed at watchdog input, CD will be discharged down to VDWL. Then reset will be set low and the watchdog circuit will be disabled. CD will be charged with the current as at power-on reset until VD reaches VDU and reset will be set high again. If a watchdog pulse will be observed before CD is discharged down to VDWL, the watchdog circuit will be enabled and CD will be charged too, but reset will not be set low. After VD has reached VDU, the periodical behavior starts again. The IC also incorporates a number of internal circuits for protection against: • Overload • Overvoltage • Overtemperature • Reverse polarity |
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Similar Description - ILE4271-2 |
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