RT6263A/B
VIN = 12V
voltage rises above VUVLO. It is to ensure that the
internal regulator is ready so that operation with
not-fully-enhanced internal MOSFET switches can be
prevented. After the device is powered up, if the input
voltage VIN goes below the UVLO falling threshold
voltage (VUVLO VUVLO), this switching will be
inhibited; if VIN rises above the UVLO rising threshold
(VUVLO), the device will resume normal operation with a
complete soft-start.
VIN
EN
SS
C
SS
x 0.7V/30μA
50μs
C
x V /6μA
FB
SS
1.9V
90% x V
OUT
VOUT
PGOOD
Output Under-Voltage Protection and Hiccup Mode
Power Good Indication
The RT6263A/B possesses output under-voltage
protection (UVP) against over-load or short-circuited
condition by constantly monitoring the feedback
voltage VFB. If VFB drops below the under-voltage
protection trip threshold (typically 65% of the internal
feedback reference voltage), the UV comparator will go
high to turn off both internal high-side and low-side
MOSFET switches. If the output under-voltage
condition continues for a period of time, the RT6263A/B
will enter output under-voltage protection with hiccup
mode. During hiccup mode, the IC will shut down for
The RT6263A/B features an open-drain output as
power-good indication to monitor the output voltage
status. The logic delay of comparator prevents false
flag as a short excursion occurs, such as line and load
transients. Tie PGOOD to VOUT or an external voltage
which is below 5.5V. The power-good function is
activated after soft-start is finished and controlled by a
comparator connected to the feedback signal VFB
.
After a certain delay time that VFB reaches the
power-good high threshold (VTH_PGLH) (typically 90%
of the reference voltage), the PGOOD pin becomes
high impedance to hold VPGOOD logic high. On the
contrary, the PGOOD pin is forced to logic-low while
tHICCUP_OFF
,
tHICCUP_OFF = CSS x 1.2V/0.86A
, and then attempt to recover automatically for
VFB falls to the power-good low threshold (VTH_PGHL
)
tHICCUP_ON
,
(typically 85% of the reference voltage). Furthermore,
this pin is also forced to logic-low as any internal
protection is triggered. The power good indication
profile is shown below.
tHICCUP_ON = CSS x 1.2V/6A.
Upon completion of the soft-start sequence, the
converter will resume normal operation if the fault
condition is removed; otherwise, the RT6263A/B stays
in auto-recovery until the fault condition is cleared.
The hiccup mode allows the circuit to operate safely
while over-load or short-circuit condition occurs, and it
makes converter resume normal operation rapidly once
the fault condition is gone.
V
TH_PGLH
V
TH_PGHL
V
FB
Abnormal case
Resume normal
detected(UV)
operation
V
PGOOD
t
= C x 1.2V/6μA
SS
HICCUP_ON
Fault condition
removed
VOUT
t
= C x 1.2V/0.86μA
SS
HICCUP_OFF
Input Under-Voltage Lockout
t
t
SS
In addition to the EN pin, the RT6263A/B also provides
enable control through the VIN pin. It features an
under-voltage lockout (UVLO) function that monitors
SW
t
the internal linear regulator (VCC). If VEN rises above
VEN_H first, switching will still be inhibited until the VIN
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is a registered trademark of Richtek Technology Corporation.
www.richtek.com
6
DS6263A/B-00 January 2020
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
