2.0A Low Output Voltage Ultra LDO Regulator
TJ2132
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.
Soft Start Time
The TJ2132 has an internal current source that charges an external slow start capacitor to implement a
slow start time. Equation 2 and Table 1 shows how to select a slow start capacitor based on an expected
slow start time. The R is 302kΩ, VO is 0.6V and i(t) is 40nA.
( )
ꢁꢁ(ꢂ) =ꢃ−ꢄꢅꢁꢁ × ꢆꢇ ꢈ ꢉ ꢊ
(2)
푉
푂
Table 1. Capacitor Values for the soft-start time
CSS
Calculated Soft-Start Time
Measured Soft-Start Time
470pF
1nF
0.56ms
1.18ms
3.18ms
6.6ms
0.64ms
1.23ms
3.44ms
7.1ms
2.7nF
5.6nF
10nF
11.8ms
12.0ms
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 TJ2132, it is recommended that additional
ceramic feed-forward capacitor be placed from OUT pin to FB 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.1)
Fig.1 Application with Decoupling & Feed-Forward Capacitor
Maximum Output Current Capability
The TJ2132 can deliver a continuous current of 2A over the full operating junction temperature range.
However, the output current is limited by the restriction of power dissipation which differs from packages.
A heat sink may be required depending on the maximum power dissipation and maximum ambient
Aug. 2014 – Rev.1.1.3
11
HTC
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
