RT6220
Functional Block Diagram
VBYP
VCC
POR &
Reference
Soft-Start
V
BOOT
SW
V
CC
CC
V
IN
Switch-Over
+
+
-
V
REF
On-Time
One shot
FB
Gate
Control
Logic
V
FB
Min off Time
V
CC
EN
PGND
VOUT
PGOOD
OCP
+
-
SW
125% x V
REF
V
OC
-
+
OVP
AGND
VIN
Fault
Logic
-
+
POK
58% x V
91.5% x V
REF
V
CC
V
CC
UVP
Regulator
+
-
REF
Operation
Overall
OCP
The RT6220 is a synchronous step-down converter with
advanced constant on-time control mode. Using the
ACOTTM control mode can reduce the output capacitance
and provide fast transient response. It can minimize the
component size without additional external compensation
network.
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.
Internal VCC Regulator
VCC Switch-Over
The regulator provides 5V power to supply the internal
control circuit. Connecting a 2.2μF ceramic capacitor for
decoupling and stability is required.
The internal regulator output will switch over to VBYP if
VBYP level is higher than 4.6V.
Power Off
Soft-Start
There is an internal discharging circuit to discharge the
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.
residual charge of output capacitor when converter is power
off.
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 ]
