FREQ datasheet(17/56 Pages) FUJITSU

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MB39A214A

Limitation : development tool vendor use only

FUJITSU SEMICONDUCTOR CONFIDENTIAL

DS405-00007-1v0-E

(7) Over Current Limitation (ILIM)

This function limits the output current when it has increased, and protects devices connected to the output.

This function detects the inductor current IL from the electromotive force of the low-side FET on-resistance

RON, and compares this voltage with the 1/5-time value of the voltage VILIM of the ILIM1 pin (pin 20) and

ILIM2 pin (pin 16) on a cyclically, using ILIM Comp. Until this voltage falls below the over current limit

value, the high-side FET is held in the off state. After the voltage has fallen below the limit value, the

high-side FET is placed into the on state. This limits the lower bound of the inductor current and also

restricts the over current. As a result, it becomes operation that the output voltage droops.

The over current limit value is set by connecting the resistor to the ILIM pin. The ILIM pin supplies the

constant current of 5 µA (Typ) . However, the current value has a temperature slope up to 4500 ppm/°C to

compensate the temperature dependence characteristics of the low-side FET on-resistance.

VOUT

DRVH

DRVL

(IOUT1

)

Output voltage setting value

Keep the off state of the high-side FET

until the detection value is gained.

Over current limit operation

Normal operation

VILIM

ILIM detection value (RON × IL =

)

FREQ Datasheet(PDF) 17 Page - fujitsu semiconductor