RT8509A
2
DS8509A-00 November 2013
www.richtek.com
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Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
Functional Pin Description
Pin No.
Pin Name
Pin Function
1 COMP
Compensation Node for Error Amplifier. Connect a series RC from COMP to
ground.
2 FB
Feedback Voltage Input. The FB regulation voltage is 1.25V nominal. Connect an
external resistive voltage divider between the step-up regulator’s output (V
OUT
)
and GND, with the center tap connected to FB. Place the divider close to the IC
and minimize the trace area to reduce noise coupling.
3
EN
Enable Control Input. Drive EN low to turn off the Boost.
4, 5, 6, 9,
13 (Exposed Pad)
GND
Ground. The Exposed Pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
7, 8
LX
Switch Node. LX is the Drain of the internal MOSFET. Connect the
inductor/rectifier diode junction to LX and minimize the trace area for lower EMI.
10 VOUT
Over-Voltage Protection Input for Boost Converter. Bypass VOUT with a
minimum 1
F ceramic capacitor directly to GND.
11 VIN
Supply Voltage Input. Bypass VIN with a minimum 1
μ
F ceramic capacitor directly
to GND.
12 SS
Soft-Start Time Setting. Connect a soft-start capacitor (C
SS
) to this pin. The
soft-start capacitor is charged with a constant current of 5
A. The soft-start
capacitor is discharged to ground when EN is low.
Pin Configurations
WDFN-12L 5x5
(TOP VIEW)
COMP
FB
GND
GND
SS
VIN
VOUT
LX
GND
EN
GND
LX
GND
13
11
10
9
1
2
3
4
5
12
6
7
8
