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ditions may occur

A) the overload is still present, and then the output power MOS is again driven in linear mode (limiting

the output current to Isc) for another Ton, starting a new cycle, or

B) the overload condition is removed, and the output power MOS is no longer driven in linear mode.

All these occurrences are presented on the DIAG2 pin (see fig 2).

We call this unique feature

Non Dissipative Short Circuit Protection and it ensures a very safe operation even

in permanent overload conditions. Note that choosing the most appropriate value for the Ton interval (i.e. the

value of the Cdon capacitor) a delay (the Ton itself) will prevent that a misleading Short Circuit information is

presented on the DIAG2 output, when driving capacitive loads (that acts like short circuit in the very beginning)

or Incandescent Lamp (a cold filament has a very low resistive value). The Non Dissipative Short Circuit Pro-

tection can be disabled (keeping Ton = 0 but with the output current still limited to Isc, and Diagnostic dis-

abled)simply shorting to ground the the ON DELAY pin.

Figure 2. Non Dissipative Short Circuit Protection Operation

DIAGNOSTIC LOGIC

The operating conditions of the device are permanently monitored and the following occurrences are signalled

via the DIAG1/DIAG2 open-drain output pins see: diagnostic Truth Table.

- Short Circuit versus ground.

- Under Voltage(UV)

- Over Temperature (OVT)

- Open Load, if the output current is less than 3mA (typical value).

DEMAGNETIZATION OF INDUCTIVE LOADS

and fast demagnetization of inductive loads without external clamping devices. The maximum energy that can

OUTPUT

CURRENT

Time

DIAG

(active low)

Time

Short Circuit

Short Circuit

Isc

Iout

D94IN105