NJW4152-AB

- 10 -

Ver.2013-01-23

Description of Block Features (Continued)

PWM Comparator Section (PWM)

This section controls the switching duty ratio.

PWM comparator receives the signal of the error amplifier and the triangular wave, and controls the duty ratio

between 0% and 100%. The timing chart is shown in Fig.1.

SW pin

FB pin Voltage

ON

OFF

OSC

Waveform

(IC internal)

Maximum duty: 100%

Fig. 1. Timing Chart PWM Comparator and SW pin

Power MOSFET (SW Output Section)

The power is stored in the inductor by the switch operation of built-in power MOSFET. The output current is limited

to 1.4A(min.)@AB version by the overcurrent protection function. In case of step-down converter, the forward

direction bias voltage is generated with inductance current that flows into the external regenerative diode when

MOSFET is turned off.

Schottky diode that has low saturation voltage.

When the power supply voltage decreases, ON resistance rises. Because a dropout voltage in the MOSFET

becomes large if an output current is large, please be careful about input-output differential voltage of the application.

In line with switching element drive, current flows into the IC according to frequency. If the power supply

impedance provided to the power supply circuit is high, it will not be possible to take advantage of IC performance

order to lower high frequency impedance.

Technical Information

NJW4152-AB Application Manual