RT6220
Functional Block Diagram
VCC
VBYP
Soft-Start
POR &
Reference
V
CC
Switch-Over
On-Time
One shot
Min off Time
V
CC
V
IN
BOOT
FB
V
REF
V
FB
+
+
-
Gate
Control
Logic
SW
V
CC
EN
VOUT
125% x V
REF
-
+
OVP
-
+
POK
58% x V
REF
+
-
UVP
SW
V
OC
+
-
Fault
Logic
V
CC
V
CC
Regulator
AGND
OCP
PGND
PGOOD
91.5% x V
REF
VIN
Operation
Overall
The RT6220 is a synchronous step-down converter with
advanced constant on-time control mode. Using the
ACOT
TM
control mode can reduce the output capacitance
and provide fast transient response. It can minimize the
component size without additional external compensation
network.
Internal VCC Regulator
The regulator provides 5V power to supply the internal
control circuit. Connecting a 2.2μF ceramic capacitor for
decoupling and stability is required.
Soft-Start
In order to prevent the converter output voltage from
overshooting during the startup period, the soft-start
function is necessary. The soft-start time is internal setting
and the duration is around 1.5ms.
VCC Switch-Over
The internal regulator output will switch over to VBYP if
VBYP level is higher than 4.6V.
Power Off
There is an internal discharging circuit to discharge the
residual charge of output capacitor when converter is power
off.
OCP
The inductor valley current is monitored cycle-by-cycle
via the internal switches, preventing an on-time until the
current drops below the current limit.
Power Good
After soft-start is finished, the power good output goes
high. The PGOOD pin is an open-drain output.
Copyright
©
2019 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS6220-10
December 2019
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
