IL44608N

Overvoltage Protection

The IL44608 offers two OVP functions:

15.4 V

– a programmable function that uses the demag pin.

The current flowing into the demag pin is mirrored and

compared to the reference current Iovp (120 µA). Thus

and is called QOVP.

In both cases, once an OVP condition is detected, the

output is latched off until a new circuit START–UP.

Start–up Management

the high voltage 9.0 mA current source is disabled and the

device starts working. The device enters into the switching

phase.

It is to be noticed that the maximum rating of the Vi

pin 8 is 500 V. ESD protection circuitry is not currently

added to this pin due to size limitations and technology

constraints. Protection is limited by the drain–substrate

junction in avalanche breakdown. To help increase the

application safety against high voltage spike on that pin it

is possible to insert a small wattage 1.0 k Ω series resistor

of no external current source providing current into the

countered in SMPS when the self supply through an auxil-

iary winding is not present (strong overload on the SMPS

output for example). The Figure 17 also depicts this work-

ing configuration. In case of the hiccup mode, the duty

cycle of the switching phase is in the range of 10%.

Mode Transition

The LW latch Figure 8 is the memory of the working

status at the end of every switching sequence.

Two different cases must be considered for the logic at

the termination of the SWITCHING PHASE:

1. No Over Current was observed

2. An Over Current was observed

These 2 cases are corresponding to the signal labeled

NOC in case of “No Over Current” and “OC” in case of

Over Current. So the effective working status at the end of

the ON time memorized in LW corresponds to Q=1 for no

over current and Q=0 for over current.

This sequence is repeated during the Switching phase.

Several events can occur:

1. SMPS switch OFF

2. SMPS output overload

3. Transition from Normal to Pulsed Mode

4. Transition from Pulsed Mode to Normal Mode

1. SMPS Switch off

When the mains is switched OFF, so long as the bulk

electrolithic bulk capacitor provides energy to the SMPS,

the controller remains in the switching phase. Then the

peak current reaches its maximum peak value, the switch-

ing frequency decreases and all the secondary voltages are

equal to 10 V, the SMPS stops working.

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