RT6263A/B
VIN = 12V
VIN
voltage rises above V
UVLO
. 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 (V
UVLO
V
UVLO
), this switching will be
inhibited; if VIN rises above the UVLO rising threshold
(V
UVLO
), the device will resume normal operation with a
complete soft-start.
Output Under-Voltage Protection and Hiccup Mode
The RT6263A/B possesses output under-voltage
protection (UVP) against over-load or short-circuited
condition by constantly monitoring the feedback
voltage V
FB
. If V
FB
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
t
HICCUP_OFF
,
t
HICCUP_OFF
= C
SS
x 1.2V/0.86A
, and then attempt to recover automatically for
t
HICCUP_ON
,
t
HICCUP_ON
= C
SS
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.
Abnormal case
detected(UV)
t
HICCUP_ON
= C
SS
x 1.2V/6μA
VOUT
t
HICCUP_OFF
= C
SS
x 1.2V/0.86μA
Resume normal
operation
Fault condition
removed
EN
50μs
C
SS
x 0.7V/30μA
C
SS
x V
FB
/6
μ
A
1.9V
SS
90% x V
OUT
VOUT
PGOOD
Power Good Indication
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 V
FB
.
After a certain delay time that V
FB
reaches the
power-good high threshold (V
TH_PGLH
) (typically 90%
of the reference voltage), the PGOOD pin becomes
high impedance to hold V
PGOOD
logic high. On the
contrary, the PGOOD pin is forced to logic-low while
V
FB
falls to the power-good low threshold (V
TH_PGHL
)
(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.
V
TH_PGLH
V
TH_PGHL
V
FB
V
PGOOD
Input Under-Voltage Lockout
t
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
the internal linear regulator (VCC). If V
EN
rises above
V
EN_H
first, switching will still be inhibited until the VIN
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
t
SS
SW
t
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
6
DS6263A/B-00
January 2020
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
