SCYW99143 Datasheet, PDF (16/35 Pages) ON Semiconductor – Universal High Voltage Control Block

CONFIDENTIAL AND PROPRIETARY
NOT FOR PUBLIC RELEASE
SCYW99143
Figure 38. Brown−out Event Detection
The Internal HV BO sensing network is formed by high
impedance resistor divider with minimum resistance of
20 MW. This solution reducing power losses during
off−mode and thus helps to pass maximum standby power
consumption limit. The internal BO network solution
provides excellent noise and PCB leakage currents
immunity that is hard to achieve when using external resistor
divider built from SMT chip resistors.
The internal HV BO sensing network output is connected
to the BO_buff bonding pad. This is buffered and trimmed
output of the HV divider. The purpose of this pad is to be
used in co−package solution with low voltage SMPS
controller to provide voltage from HV pad into slave (low
voltage) controller. The ratio between voltage on HV pad
and voltage on BO_buff pad is defined by VBO_buff_ratio
parameter.
X2 Discharge Circuitry
The SCYW99143 X2 discharge circuitry uses dedicated
pin (X2) together with external charge pump sensing
network to detect whether is application plugged into the
mains or not. Advantage of this solution is that the internal
IC consumption can be reduced to extremely low level by
keeping all internal blocks unbiased except simple and low
consuming X2 timer disable circuitry. The internal X2 timer
with duration of X2_timer is used to overcome unwanted
activation of the X2 and Vcc discharge switches in case of
AC line dropout. The internal X2 and Vcc discharge
switches are activated once the X2 timer elapses. The HV
startup current source is enabled in the same time thus the
discharge path for X2 capacitor exists – refer to Figure 39.
Figure 39. Simplified Block Diagram of X2 Capacitor Discharge Circuitry
The time duration of X2 capacitors discharging could be calculated by:
t
+
U_CX1.2
I_{_X2_dis}
@
C_X1,2
http://onsemi.com
16
(eq. 1)