3A Ultra Low Dropout Linear Regulator
APPLICATION INFORMATION
Introduction
TJ4230
TJ4230 is intended for applications where high current capability and very low dropout voltage are required. It
provides a simple, low cost solution that occupies very little PCB estate. Additional features include an enable
pin to allow for a very low power consumption standby mode, an adjustable pin to provide a fully adjustable
output voltage, and SENSE pin to provide better remote load regulation characteristics.
Component Selection
Input Capacitor :
A large bulk capacitance over than 10uF should be closely placed to the input supply pin of the TJ4230 to
ensure that the input supply voltage does not sag. Also a minimum of 10uF ceramic capacitor is
recommended to be placed directly next to the V
IN
Pin. It allows for the device being some distance from any
bulk capacitor on the rail. Additionally, input droop due to load transients is reduced, improving load transient
response. Additional capacitance may be added if required by the application.(See Fig.1)
Output Capacitor :
A minimum ceramic capacitor over than 10uF should be very closely placed to the output voltage pin of the
TJ4230. Increasing capacitance will improve the overall transient response and stability.
Decoupling (Bypass) Capacitor :
In very electrically noisy environments, it is recommended that additional ceramic capacitors be placed from
VIN to GND. The use of multiple lower value ceramic capacitors in parallel with output capacitor also allows to
achieve better transient performance and stability if required by the application.(See Fig.1)
Feed-Forward Capacitor
To get the higher PSRR than the inherent performance of TJ4230, it is recommended that additional ceramic
feed-forward capacitor be placed from VOUT pin to ADJ pin. The capacitance of feed-forward capacitor with
range of 10pF to 1uF allows to achieve better PSRR performance when required by the application.(See
Fig.2)
VIN
R
P
C
IN
10uF
CC1
EN
V
IN
V
OUT
VOUT
VIN
R
P
V
IN
V
OUT
VOUT
CFF
ADJ
R1
R2
C
OUT
10uF
CC2
TJ4230
GND
SENSE
C
OUT
10uF
CC2
C
IN
10uF
CC1
TJ4230
EN
GND
Fig. 1. Application with Decoupling Capacitor,
CC1 & CC2
Fig. 2. Application with Feed-Forward Capacitor,
CFF
Delayed Start-Up
When power sequence control is required or rising time of input supply voltage is over than 100usec, it is
recommended to apply delayed start-up by using Cdelay as shown in Fig. 3. It can adjust proper delay by
Rp-Cdelay time constant. And also it can prevent any unexpected transient characteristics at output voltage
when the rising time of input supply voltage is as long as 100usec or longer.
VIN
R
P
C
IN
10uF
C
delay
EN
V
IN
V
OUT
VOUT
CFF
ADJ
R1
R2
C
OUT
10uF
TJ4230
GND
Fig. 3. Application with Delayed Start-Up
Apr. 2011 – Rev. 1. 0
6/9
HTC
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
