MS1003SH datasheet(11/41 Pages) SHINDENGEN

11 / 41 page

MS1003SH･MS1004SH

Application Note Ver.2.2

SHINDENGEN ELECTRIC MFG. CO. , LTD

11/41

3.2.5 Output voltage control

The MS1003SH and MS1004SH control the output

voltage with the ON range proportional to the voltage at

the F/B pin.

The output voltage is controlled linearly so that the ON

range is at its minimum when the F/B pin voltage is 1.5

V and at its maximum when the voltage is 4.5 V. The

IF/B current flows from the F/B pin. The impedance of

the photocoupler transistor externally connected between

the F/B pin and the GND pin is varied by a control signal

from the secondary output detection circuit, thereby

controlling the ON range of the main switching device to

produce a constant voltage.

The latch count start voltage (VF/B (latch count))

is set up for the F/B pin. When the voltage exceeds

the set level, the timer begins counting. After

maintaining this state for approximately 2 s (latch

count), the IC is latched.

3.3 Burst mode oscillation

3.3.1 AutoStby function

The MS1003SH and MS1004SH switch between normal mode and burst mode automatically. This enables

low standby power consumption with no other components required for standby mode.

1) Switching from normal mode to burst mode

The IC switches from normal mode to burst mode when the load becomes lighter and the OCL pin

detects a drain current at the VOCL (stby) = 45 mV (TYP) or less for longer than Tstby = 250 ms (TYP).

ton

(max)

1.5

4.5

フィードバック電圧

VF/B［V］

VF/B(latch count)

Controlling output

voltage with

photocoupler

Output voltage error

detection feedback

signal

F/B pin

Feedback voltage

Normal

Operating

mode

VOCL (stby) =

45 mV or less

Burst

The IC enters standby mode when the

drain current stays at the burst

switching current or below for longer

than Tstby = 250 ms.

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