SCYW99143 Datasheet, PDF (19/35 Pages) ON Semiconductor – Universal High Voltage Control Block

SCYW99143
CONFIDENTIAL AND PROPRIETARY
NOT FOR PUBLIC RELEASE
Auto−recovery UVP on VCC
The controller activates auto−recovery timer with
duration T_{A−rec_timer} in case the Vcc drops below Vcc_off
level. The Vcc capacitor is discharged down to Vcc_bias
level when auto−recovery timer starts counting. The Vcc is
maintained at Vcc_bias level (5 V) during this operation to
keep the timer and other internal circuitry running.
The Vcc capacitor is fully discharged by X2 discharge
switch before controller tries for restart from fault condition.
The restart from fault condition occurs when
auto−recovery timer elapses or if Vcc is forced below 4 V
externally.
Internal Communication between Two Controllers at
Co−package Option
Co−package option can bring some benefits.
SCYW99143 can obtain information about VCC_on of
slave controller, and information about slave controller
transition to Latch−off mode.
VCC_ON Detection
The SCYW99143 features VCC_stop bonding pad/input
that can be used to terminate startup current source operation
prior the regular Vcc_on threshold (22 V typically) is
reached. This feature reduces startup time in case the slave
SMPS controller provides VCC_stop signal based on its own
Vcc_on threshold (like 18 V in NCP1250 case). Difference
between start up sequences with and without VCC_stop
bonding interconnection can be seen in Figure 43. Vcc_stop
comparator is enabled only during start−up sequence − i.e.
Vcc capacitor is charged from Vcc_off level to Vcc_on
level.
Figure 43. Start−up Sequence Without and With VCC_start Signal Interconnection
LATCH Detection
The SCYW99143 latch pad can be used to latch the HV
startup block off in case of serious fail in SMPS. The internal
latch signal from slave SMPS controller has to be provided
to SCYW99143 in case of co−packaged solution. When the
slave controller Latches−off without inter−bonding Latch
information, the SCYW99143 detects only that Vcc was lost
because of missing driver pulses i.e. no power from
auxiliary winding. The SCYW99143 goes then into
auto−recovery mode and restarts operation after T_{A−rec_timer}
by a new start−up sequence refer to Figure 49. If the slave
controller latches−off and inter−bonding Latch information
is provided, the SCYW99143 goes into latch−off mode refer
to Figure 50. Latch−off mode continues until the mains is
unplugged – the X2 discharge is confirmed and activated or
Vcc is forced below 4 V externally. The inter−bonding Latch
signal does not have to be present for the time the controller
is latched − the SCYW99143 internal logic triggers on rise
edge of this signal only. More details are showed on
Figure 44. Latch comparator is enabled only during regular
operation − i.e. when Vcc level is between Vcc_on and
Vcc_off levels.
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