SHINDENGEN

ELECTRIC MFG.CO.,LTD

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2.8.4 Output diode short protection

Master

A short-circuited output diode results in the detection of an overcurrent, and the internal counter of

the master IC begins counting. Once the counter counts to 512, the IC is latched and stopped.

This function prevents the IC from continuing to operate with the diode short-circuited. For

unlatching, the VCC voltage needs to be discharged and then input again.

The internal counter is reset when the Z/C pin reaches 4 V or more to disable the function at startup

or in the event of an overload.

Fig. 19 shows the sequence of steps involved in the output diode short protection feature of a master

IC. When the output diode of a slave IC is short-circuited, the IC is latched and stopped in a similar

sequence.

Fig. 19 Operating sequence in output diode short protection

2.8.5 VCC pin undervoltage protection (UVLO)

Master

Slave

To turn VCC on and off safely, the oscillation start/stop voltages differ between the master IC and

the slave IC. When a voltage is applied to the VCC pin, the slave IC is activated first to ensure

that the slave IC will be stable when the master IC is activated. When the voltage supply to VCC

is stopped, the master IC stops first to ensure that all the ICs stop safely.

The table below shows the absolute maximum rating and oscillation start and stop voltages of the

VCC pin.

Voltage between

VCC & GND

Master IC

MH2501SC

Slave IC

MH2511SC

Absolute maximum

rating

26 V (common to master and slave)

Oscillation start

voltage

11 V

9.5 V

(starts earlier)

Oscillation stop

voltage

9 V

(stops earlier)

7.5 V

2.8.6 Thermal shutdown

Master

Oscillation stops if the master IC generates excessive heat for any reason and when the IC junction

temperature exceeds the operation stop temperature (TSD) of 130°C. If the IC junction temperature

falls to about 70°C, oscillation resumes automatically.