DS8409 Datasheet, PDF (3/11 Pages) Richtek Technology Corporation – Green Mode Buck Converter

Functional Block Diagram
VCC
RT8409
Regulator
FB
+
EA
State Machine
A
-
+
-
1.75V
DRAIN
SGND
COMP SENSE
Operation
The RT8409 senses the output voltage via the bootstrap
loop. The output voltage feedback signal is compared to
an internal reference voltage for the output voltage
regulation. The COMP pin, which is the operational
amplifier output node, is used for the control loop
compensation to obtain stable response. To stabilize the
system properly select the compensation network is
required.
The FB pin is the voltage loop input for the system
regulation. The above COMP pin related compensation
will be determined by specified system demand and be
adapted to various applications.
Burst Mode
For the no load power saving demand, burst mode is a
way to save power and maintain output regulation. High
efficiency is achieved at light loads when Burst Mode
operation is entered. The typical burst mode trigger levels
are defined as follows. The MOSFET will stop switching
when VC voltage goes lower than 200mV (typ.). The
MOSFET will resume switching again once the VC voltage
goes higher than 300mV (typ.).
In this mode the output ripple has a variable frequency
component that depends upon load current. Burst Mode
operation ripple can be reduced slightly by using more
output capacitance.
VC
VC.high
VC.low
VDS
I_OUT
Copyright ©2016 Richtek Technology Corporation. All rights reserved.
DS8409-00 September 2016
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
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