300mA Ultra Low Dropout Linear Regulator
APPLICATION INFORMATION
TJ4203
Introduction
TJ4203 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 minimum of 1uF ceramic capacitor is recommended to be placed directly next to the VIN 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 1uF should be very closely placed to the output voltage pin of the
TJ4203. 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 TJ4203, 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 1nF to 100nF allows to achieve better PSRR performance when required by the application. In this
case, over than 2.2uF output capacitor should be placed to the output voltage pin of the TJ4203.(See Fig.2)
VIN
VIN
VOUT
VOUT
VIN
VIN
VOUT
VOUT
TJ4203
TJ4203
RP
RP
CFF
R2
R1
CIN
1uF
COUT
1uF
CIN
1uF
COUT
2.2uF
CC1
CC2
CC1
CC2
EN
SENSE
EN
ADJ
GND
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
VIN
VOUT
ADJ
VOUT
TJ4203
RP
CFF
R2
R1
COUT
2.2uF
CIN
EN
1uF
GND
Cdelay
Fig. 3. Application with Delayed Start-Up
Apr. 2011 – Rev.1.0
6/10
HTC
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
