RT6576C/D
Functional Block Diagram
BOOT1
UGATE1
PHASE1
LDO5
Channel 1
Buck
Controller
Channel 2
Buck
Controller
LDO5
BOOT2
UGATE2
PHASE2
LGATE1
FB1
CS1
BYP1
VCLK
LGATE2
FB2
CS2
PGOOD
OSC
GND
SW5 Threshold
BYP1
Power-On
Sequence
Clear Fault Latch
EN1
EN2
LDO5
LDO5
VIN
REF
LDO3
BYP1
LDO3
Operation
The RT6576C/D includes two constant on-time
synchronous step-down controllers and two linear
regulators.
Buck Controller
In normal operation, the high-side N-MOSFET is turned
on when the output is lower than VREF, and is turned off
after the internal one-shot timer expires. While the high-
side N-MOSFET is turned off, the low-side N-MOSFET is
turned on to conduct the inductor current until next cycle
begins.
Soft-Start
For internal soft-start function, an internal current source
charges an internal capacitor to build the soft-start ramp
voltage. The output voltage will track the internal ramp
voltage during soft-start interval.
PGOOD
The power good output is an open-drain architecture. When
the two channels soft-start are both finished, the PGOOD
open-drain output will be high impedance.
Current Limit
The current limit circuit employs an unique
“valley”
current
sensing algorithm. If the magnitude of the current sense
signal at PHASE is above the current limit threshold, the
PWM is not allowed to initiate a new cycle. Thus, the
current to the load exceeds the average output inductor
current, the output voltage falls and eventually crosses
the under-voltage protection threshold, inducing IC
shutdown.
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS6576C/D-03
February 2016
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
