RT7285C
2
DS7285C-03 July 2014
www.richtek.com
©
Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
Functional Pin Description
Pin No.
SOT-23-6 TSOT-23-6
Pin Name
Pin Function
1 1
BOOT
Bootstrap Supply for High-Side Gate Driver. Connect a 0.1
F ceramic
capacitor between the BOOT and SW pins.
2 2
GND
Power
Ground.
3 3
FB
Feedback Voltage Input. The pin is used to set the output voltage of the
converter via a resistive divider. The converter regulates V
FB
to 0.6V
4 4
EN
Enable Control Input. Connect EN to a logic-high voltage to enable the IC or to
a logic-low voltage to disable. Do not leave this high impedance input
unconnected.
5 5
VIN
Power Input. The input voltage range is from 4.3V to 18V. Must bypass with a
suitable large ceramic capacitor at this pin.
6
6
SW
Switch Node. Connect to external L-C filter.
Function Block Diagram
Operation
The RT7285C is a synchronous step-down converter with
advanced constant on-time control mode. Using the ACOT
control mode can reduce the output capacitance and fast
transient response. It can minimize the component size
without additional external compensation network.
Current Protection
The inductor current is monitored via the internal switches
cycle-by-cycle. Once the output voltage drops under UV
threshold, the RT7285C will enter hiccup mode.
UVLO Protection
To protect the chip from operating at insufficient supply
voltage, the UVLO is needed. When the input voltage of
VIN is lower than the UVLO falling threshold voltage, the
device will be lockout.
Thermal Shutdown
When the junction temperature exceeds the OTP
threshold value, the IC will shut down the switching
operation. Once the junction temperature cools down and
is lower than the OTP lower threshold, the converter will
autocratically resume switching.
Comparator
VIBIAS
BOOT
GND
SW
PVCC
EN
Driver
GND SW
Control
EN
UV & OV
OC
Min off
PVCC
FB
Reg
V
REF
V
IN
VIN
On-Time
V
IN
SW
PVCC
UGATE
LGATE
+
-
-
Ripple
Gen.
SW
