AP139
300mA Low-Noise CMOS LDO
Typical Performance Characteristics (Continued)
Vcc Vs Short Current
400
350
300
Short Current (mA)
250
200
150
100
50
0
3.5
Top to bottom
Vout=1.5V
Vout=1.8V
Vout=2.5V
Vout=3.3V
4
4.5
5
5.5
6
6.5
7
Vcc (V)
Function Description
The AP139 of CMOS regulators contain a PMOS
pass transistor, voltage reference, error amplifier,
over-current protection, thermal shutdown.
The P-channel pass transistor receives data from
the error amplifier, over-current protection, and
thermal protection circuits. During normal operation,
the error amplifier compares the output voltage to a
precision reference. Over-current and thermal
shutdown circuits become active when the junction
temperature exceeds 130
o
C, or the current exceeds
300mA. During thermal shutdown, the output
voltage remains low. Normal operation is restored
when the junction temperature drops below 110
o
C.
The AP139 switches from voltage mode to current
mode when the load exceeds the rated output
current. This prevents over-stress.
Enable
The enable pin normally floats high. When actively,
pulled low, the PMOS pass transistor shut off, and
all internal circuits are powered down. In this state,
the quiescent current is less than 2µA. This pin
behaves much like an electronic switch.
External Capacitor
The AP139 is stable with a low ESR output
capacitor to ground of 1.0µF or greater. It can keep
stable even with higher ESR capacitors. A second
capacitor is recommended between the input and
ground to stabilize VIN. The input capacitor should
be larger than 0.1µF to have a beneficial effect. All
capacitors should be placed in close proximity to
the pins. A “quiet” ground termination is desirable.
Anachip Corp.
www.anachip.com.tw
5/8
Rev.1.1 Jun 02, 2006
ANACHIP [ ANACHIP CORP ]
