AME8804_12 Datasheet, PDF (7/18 Pages) Analog Microelectronics – 300mA CMOS LDO

AME
AME8804
300mA CMOS LDO
n Detailed Description
The AME8804 family of CMOS regulators contain a
PMOS pass transistor, voltage reference, error amplifier,
over-current protection, thermal shutdown, and Power
Good detection circuitry.
The P-channel pass transistor receives data from the
error amplifier, over-current shutdown, and thermal pro-
tection circuits. During normal operation, the error ampli-
fier compares the output voltage to a precision reference.
Over-current and Thermal shutdown circuits become ac-
tive when the junction temperature exceeds 150^oC, or
the current exceeds 300mA. During thermal shutdown,
the output voltage remains low. Normal operation is re-
stored when the junction temperature drops below 120^oC.
The AME8804 switches from voltage mode to current
mode when the load exceeds the rated output current.
This prevents over-stress. The AME8804 also incorpo-
rates current foldback to reduce power dissipation when
the output is short circuited. This feature becomes active
when the output drops below 0.8volts, and reduces the
current flow by 65%. Full current is restored when the
voltage exceeds 0.8 volts.
n Enable
The Enable pin normally floats high. When actively,
pulled low, the PMOS pass transistor shuts off, and all
internal circuits are powered down. In this state, the qui-
escent current is less than 1µA. This pin behaves much
like an electronic switch.
n Power Good
The AME8804 (SOT-26/TSOT-26 package only) includes
the Power Good feature. When the output is not within
+10% of the specified voltage, it pulls low. This can occur
under the following conditions:
1) Input Voltage too low.
2) During Over-Temperature.
3) During Over-Current.
4) If output is pulled up.
(Note: PG pin is an open-drain output.)
n External Capacitors
The AME8804 is stable with an output capacitor to
ground of 2.2µF or greater. Ceramic capacitors have the
lowest ESR, and will offer the best AC performance. Con-
versely, Aluminum Electrolytic capacitors exhibit the high-
est ESR, resulting in the poorest AC response. Unfortu-
nately, large value ceramic capacitors are comparatively
expensive. One option is to parallel a 0.1µF ceramic ca-
pacitor with a 10µF Aluminum Electrolytic. The benefit is
low ESR, high capacitance, and low overall cost.
A second capacitor is recommended between the in-
put and ground to stabilize Vin. The input capacitor should
be at least 0.1µF to have a beneficial effect.
All capacitors should be placed in close proximity to
the pins. A "Quiet" ground termination is desirable. This
can be achieved with a "Star" connection.
Rev.K.04
7