400EABBA2 datasheet(28/47 Pages) ONSEMI

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NCP12400

www.onsemi.com

Figure 55. HV Pin ac Input Timing Diagram with X2 Capacitor Discharge Sequence When the Application is

Unplugged Under High Line Condition

time

VHV

One Shot

time

DRV

VHV(start)

VHV(stop)

tDET

time

X2 discharge

current

t DIS

X2 discharge

AC line unplug

X2 capacitor

discharge

AC line Unplug

detector starts

tDET

tDIS

X2 capacitor

discharge

Device is stopped

No AC detection

timer

restarts

timer

starts

X2 discharge

Starts

only at

VCC(on)

VCC

VCC(dis)

tHV

Device shunts the

X2 discharge

current internally

time

The Low Consumption Off Mode

There was implemented the low consumption off mode

allowing to reach extremely low no load input power as

described in previous chapters. If the voltage at feedback pin

decreases below the 0.6 V the controller enters the off mode.

The internal VCC is turned−off, the IC consumes extremely

low VCC current and only the voltage at external VCC

capacitor is maintained by the Dynamic Self−Supply circuit.

The Dynamic Self−Supply circuit keeps the VCC voltage

between the VCC(on) and VCC(off) levels. The supply for the

FB pin watch dog circuitry and FB pin bias is provided via

the low consumption current sources from the external VCC

capacitor. The controller can only start, if the FB pin voltage

increases above the 2.2 V level. See Figure 56 for timing

diagrams.

Only the X2 cap discharge and Self−Supply features is

enabled in the low consumption off mode. The X2 cap

discharging feature is enable due the safety reasons and the

Self−Supply is enabled to keep the VCC supply, but only

very low VCC consumption appears in this mode. Any other

features are disabled in this mode.

The information about the latch status of the device is kept

in the low consumption off mode and this mode is used for

the TSD protection as well. The protection timer

GoToOffMode tGTOM is used to protect the application

against the false activation of the low consumption off mode

by the fast drop outs of the FB pin voltage below the 0.4 V

level. E.g. in case when is present high FB pin voltage ripple

during the skip mode.

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