SCYW99143 Datasheet, PDF (17/35 Pages) ON Semiconductor – Universal High Voltage Control Block

SCYW99143
CONFIDENTIAL AND PROPRIETARY
NOT FOR PUBLIC RELEASE
The X2 capacitor discharging process can be interrupted
by increasing voltage on X2 pin back above Vth_X2.
The over temperature protection block is active during
discharging process to protect controller chip against
unwanted overheat that could occur in case the X2 pin is
opened and the high voltage is present on the HV pin (like
during open – short pins testing for instance).
The X2 discharge switch is also activated to discharge Vcc
capacitor when entering into fault mode (latch mode,
auto−recovery mode or the HV pin voltage drops below
VBO_off threshold for more than 50 ms), off−mode and also
before controller Vcc restart.
Refer to controller operation sequencing section – cases
1 − 5 for better understanding on how the SCYW99143 X2
discharge circuitry works.
Remote Input
The SCYW99143 features dedicated input (Remote pin)
that allows user to activate ultra low consumption mode
during which the IC consumption is reduced to only very
low HV pin leakage current (refer to IHV_off−mode_1 and
IHV_off_ mode_2 parameters). The off−mode is activated
when remote pin voltage exceeds V_REM_off threshold
(8 V typically for Active_ON version) or drops under
V_REM_off threshold (0.4 V Typically for Active _OFF
version). Normal operating mode (i.e. on−mode) is then
initiated again when remote input voltage crosses back
V_REM_on threshold (1.5 V typically Active_ON version
and 2 V typically Active_OFF version) – refer to Figure 40
or Figure 41 for better understanding.
Active ON Off−mode
The off−mode with active ON logic works in such a way
that the off−mode is activated when the remote input is
pulled up by auxiliary remote supply (refer to Figure 40.).
The normal operation mode is then activated when
dedicated opto−coupler pulls the remote input down. There
could occur situation, in the application, that the auxiliary
remote supply stays charged while the secondary bias has
been lost. The application then cannot restart until the
auxiliary remote supply capacitor fully discharges. Thus the
remote input hosts internal pull down switch and remote
timer with duration REM_timer. The controller pulls down
remote pin using this circuitry in order to allow correct
application restart in case the auxiliary bias capacitor (C7)
stays charged while the secondary side is fully discharged
already. The remote timer is activated each time the
application starts after these events:
• Start after application was plugged into the mains (X2
discharger signal resets remote timer latch in this case)
• Restart from fault conditions in auto−recovery versions
• Restart after Vcc has been lost while remote pin was at
low state
• Restart after BO event
• Restart after OTP event
Figure 40. Simplified Block Diagram of Remote Control Input for Active ON Off−mode
The remote timer helps to assure correct application start
or re−start from fault conditions by forcing controller
operation for REM_timer duration. However, the secondary
controller drives remote pin via opto−coupler during normal
operating conditions in order to switch between on−mode
and off−mode states. The on−mode is activated for very
short time during no−load conditions − just to re−fill primary
and secondary capacitors to keep application biased. The
remote timer thus cannot be used in this case because it
would increase no−load power consumption by forcing
application on−mode operation for longer time than it is
naturally needed. The remote timer with internal pull down
switch is thus not activated in this case (i.e. when application
restarts from off−mode operation).
Refer to controller operation sequencing section – cases
1 − 5 for better understanding on how the SCYW99143
remote circuitry works.
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