RT2825
Functional Block Diagram
VINR
Internal
Regulator
PVCC
VCC
VCC
VIN1
EN1
RLIM1
SS1
BOOT1
LX1
Buck 1
FB1
COMP1
AGND
VCC PVCC
BOOT2
PGND1
ROSC
OSC
VIN2
EN2
RLIM2
SS2
LOWP
PG1
PG2
Power
Good
Buck 2
LX2
FB2
COMP2
AGND
PGND2
AGND
Operation
UV Comparator
If the feedback voltage (V
FB
) is lower than threshold voltage
(91% of V
REF
), the UV Comparator's output goes high
and the logic control circuit is allowed to turn on the
MOSFET to pull PG1/PG2 pin to low.
OV Comparator
If the feedback voltage (V
FB
) is higher than threshold voltage
(109% of V
REF
), the OV Comparator's output goes high
and the logic control circuit is allowed to turn on the
MOSFET to pull PG1/PG2 pin to low.
Voltage Reference
The converter produces a precise
±1%
voltage reference
over-temperature by scaling the output of a temperature
stable bandgap circuit.
Error Amplifier
The device uses a transconductance error amplifier. The
error amplifier compares the FB pin voltage with the SS
pin voltage and the internal reference voltage which is 0.6V.
The transconductance of the error amplifier is 1300
μA/V
during normal operation. The compensation network should
be connected between the COMP pin and ground.
Oscillator with RT/SYNC Function
The switching frequency is adjustable by an external
resistor connected between the ROSC pin and GND. The
available frequency range is from 200kHz to 1MHz. An
internal synchronized circuit has been implemented to
switch from RT mode to SYNC mode. To implement the
synchronization function, connect a square wave clock
signal to the ROSC pin with a duty cycle between 10% to
90%. The switching cycle is synchronized to the falling
edge of the external clock at ROSC pin.
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS2825-00 May 2017
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
