RT6343
The equation below assumes that the VFB will be 0 at
short-circuited condition and it can be used to calculate
the CSS/TR discharging time (tSS_DIS2) and charging time
(tSS_CH) during hiccup mode.
1.146
tSS_DIS2 = CSS
ISS_DIS
1.146
tSS_CH = CSS
ISS_CH
Output Over-Voltage Protection
The RT6343 includes an output over-voltage protection
(OVP) circuit to limit output voltage. Since the VFB is lower
than the reference voltage (VREF) at over-load or short-
circuited condition, the COMP voltage will be high to
demand maximum output current. Once the over-load or
short-circuited condition is removed, the COMP voltage
resumes to the normal voltage to regulate the output
voltage. The output voltage leads to the possibility of an
output overshoot if the load transient is faster than the
COMP voltage transient response, especially for small
output capacitance. If the VFB goes above the 109% of
the reference voltage, the high-side MOSFET will be forced
off to limit the output voltage. When the VFB drops lower
than the 106% of the reference voltage, the high-side
MOSFET will be resumed.
Over-Temperature Protection
The RT6343 includes an over-temperature protection (OTP)
circuitry to prevent overheating due to excessive power
dissipation. The OTP will shut down switching operation
when junction temperature exceeds a thermal shutdown
threshold TSD. Once the junction temperature cools down
by a thermal shutdown hysteresis (ΔTSD), the IC will
resume normal operation with a complete soft-start.
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS6343-00 October 2019
www.richtek.com
9
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