HA16108FP View Datasheet(PDF) - Hitachi -> Renesas Electronics

Part Name

Description

View to exact match

HA16108FP

PWM Switching Regulator for High-performance Voltage Mode Control

Hitachi -> Renesas Electronics 

HA16107P/FP, HA16108P/FP

3. Programming of Maximum ON-Duty (Du Max)

The preceding equations should be used to program the deadband or maximum ON-duty. The

following table gives a summary.

Condition

Triangle

waveform

RT1 > RT2

RT1 = RT2

RT1 < RT2

Du max

Less than 50%

50%

Greater than 50%*

Note: In a primary-control switching regulator, Du Max > 50% is dangerous because the transformer will

saturate.

Soft Start and Quick Shutdown

One purpose of the soft-start function is to protect the switching controller and power MOSFET from

surges at power-up. Another purpose is to let the secondary-side DC voltage rise smoothly.

When power goes off, the quick-shutdown function rapidly discharges the capacitor in the soft-start circuit

(and at the same time switches the PWM output off) to prepare for the next power-on.

The soft-start function in these ICs lets the PWM output develop smoothly from zero to the designated

pulse width at power-up. The soft-start voltage is the 3.8 V voltage value of an internal Zener diode, so the

PWM output is able to start widening gradually as soon as the soft-start function starts operating. The soft-

start function will start promptly even if CST is large.

The soft-start and quick-shutdown modes are selected automatically in the IC, under control of the UVL

signal.

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