MS1003SH datasheet(12/41 Pages) SHINDENGEN

12 / 41 page

MS1003SH･MS1004SH

Application Note Ver.2.2

SHINDENGEN ELECTRIC MFG. CO. , LTD

12/41

2) Burst mode control

In burst mode, the OCL pin detects the drain current, and every pulse is limited to VTH (stby) = 60 mV

(TYP) to control oscillation.

Output voltage is controlled linearly in normal mode. In burst mode, oscillation begins when the F/B pin

voltage VF/B reaches the VF/B (stby start) = 1.8 V (TYP) and stops when the voltage falls to the VF/B

(stby stop) = 0.8 V (TYP). This control causes voltage ripples and intermittent oscillation, reducing

switching loss per unit time and thereby reducing standby power consumption.

The following thresholds also change from normal mode:

 The thresholds for oscillation stop voltage and the startup circuit on voltage are reduced by 1 V

from normal mode.

VCC (stop normal) = 8 V (TYP)

 VCC (stop stby) = 7 V (TYP)

VCC (startup on normal) = 9 V (TYP)

 VCC (startup on stby) = 8 V (TYP)

These allow easy adjustment of the Vcc setting in standby mode and further reduce power consumption.

3) Switching from burst mode to normal mode

The IC switches automatically to normal mode when the load becomes heavier and the VF/B voltage

rises and exceeds VF/B (stby reset) = 3V (TYP).

The thresholds changed at standby return to previous levels when the IC returns from burst mode to

normal mode. At the same time, soft start activates for approximately 1/70 of the normal startup to

prevent jitter and other problems during mode switching.

Soft start for approx. 1/70 of normal startup

Normal

Burst

Operating

mode

MS1003SH Datasheet(PDF) 12 Page - Shindengen Electric Mfg.Co.Ltd