MS1003SH datasheet(33/41 Pages) SHINDENGEN

33 / 41 page

MS1003SH･MS1004SH

Application Note Ver.2.2

SHINDENGEN ELECTRIC MFG. CO. , LTD

33/41

Initial design value

Recommended value

R310

560



220

–1 k

DZ303

18 V

16 V–22 V

* Keep in mind potential losses associated with R310.

This measure will improve the regulation

(represented by the red line) and move it to the

black line on the chart to the right. The voltage

setting of DZ303 is the operating point of DZ303, as

shown to the right.

This circuit incorporating this measure is the most

effective circuit available when using super standby

mode. No losses occur in super standby mode.

(4) Measure  against poorly regulated Vcc voltage

If the measures described in Section (2) and (3) above do not work, use a dropper circuit as shown below

to stabilize Vcc. Use the constants given below as guidelines.

When selecting DZ304, note the withstand voltage between Q306 and EB.

If the withstand voltage between Q306 and EB is 5 V, select 22 V or greater.

If the withstand voltage between Q306 and EB is 7 V, select 20 V or greater.

This measure stabilizes the Vcc pin voltage to the zener

voltage of DZ304 plus VBE of Q306. Unless DZ305 is

added as shown in the diagram above, OVP of the Vcc

pin cannot be used. Set the zener voltage of DZ305 so

that the OVP functions properly.

The chart to the right shows a Vcc regulation model

after implementing the measures above. Activating the

dropper circuit stabilizes the voltage. When DZ305

activates, the voltage becomes the OVP voltage.

Previous Vcc

regulation

OVP voltage

Operating point of

DZ303

Output power

Operating point of

dropper circuit

Previous Vcc

regulation

OVP voltage

Operating point of

DZ305

Output power

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