RT2852BH
Functional Block Diagram
PGOOD EN
UV
Comparator
91% V
REF
PGOOD
Logic
109% V
REF
OV
Comparator
V
EN
= 1.21V
Slope
Compensation
I
SS
SS/TR
FB
V
REF
+
+
-
Current
Comparator
High-Side
Current Sense
VIN
PVIN
I
P
I
hys
Thermal
Detector
UVLO
Regulator
Shutdown
Logic
Shutdown
BOOT
Power Stage
Control
Logic,
Driver, and
Boot UVLO
LX
Voltage
Reference
Oscillator with
RT/SYNC
Function
COMP
RT/SYNC
Low-Side
Current Sense
GND
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 PGOOD 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 PGOOD 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/
TR pin voltage and the internal reference voltage which is
0.8V. 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 RT/SYNC pin and GND.
The available frequency range is from 200kHz to 1.2MHz.
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 RT/SYNC pin with a duty cycle between
10% to 90%. The switching cycle is synchronized to the
falling edge of the external clock at RT/SYNC pin.
Copyright
©
2019 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS2852BH-01
June
2019
www.richtek.com
3
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
