RT5711C
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
2
3
4
NC
No internal connection.
Enable control input.
EN
VIN
Supply voltage input. The RT5711C operates from a 2.5V to 6V input.
Switch node.
LX
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum thermal dissipation.
5, 7 (Exposed Pad) GND
FB
6
Feedback.
Functional Block Diagram
EN
VIN
UVLO
Shut Down
Control
LX
Ton
OTP
VIN
Error
Amplifier
Comparator
Logic
-
+
FB
+
-
Control
Driver
LX
V
REF
R
COMP
C
Current
Limit
C
GND
Detector
LX
Current
Sense
Operation
The RT5711C is a synchronous low voltage step-down
converter that can support the input voltage range from
2.5V to 6V and the output current can be up to 1.5A.
The RT5711C uses a constant on-time, current mode
architecture. In normal operation, the high side
P-MOSFET is turned on when the switch controller is
set by the comparator and is turned off when the Ton
comparator resets the switch controller.
UV Comparator
If the feedback voltage (VFB) is lower than threshold
voltage 0.2V, the UV comparator's output will go high
and the switch controller will turn off the high side
MOSFET. The output under voltage protection is
designed to operate in Hiccup mode.
Enable Comparator
A logic-high enables the converter; a logic-low forces
the IC into shutdown mode.
Low side MOSFET peak current is measured by
internal RSENSE. The error amplifier EA adjusts
COMP voltage by comparing the feedback signal (VFB
)
Soft-Start (SS)
from the output voltage with the internal 0.6V reference.
When the load current increases, it causes a drop in
the feedback voltage relative to the reference, then the
COMP voltage rises to allow higher inductor current to
match the load current.
An internal current source charges an internal capacitor
to build the soft-start ramp voltage. The VFB voltage will
track the internal ramp voltage during soft-start interval.
The typical soft-start time is 1.2ms.
Copyright © 2019 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS5711C-04 December 2019
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
