AME8848 Datasheet, PDF (6/11 Pages) AMETHERM Circuit Protection Thermistors – 1A CMOS LDO

AME
AME8848
n Detailed Description
The AME8848 of CMOS regulators contains a PMOS
pass transistor, voltage reference, error amplifier, over-
current protection, and thermal shutdown.
The P-channel MOSFET pass transistor receives data
from the error amplifier, over-current shutdown, and ther-
mal protection circuits. During normal operation, the er-
ror amplifier compares the output voltage to a precision
reference. Over-current and Thermal shutdown circuits
become active when the junction temperature exceeds
150^oC, or the current exceeds 1100mA. During thermal
shutdown, the output voltage remains low. Normal op-
eration is restored when the junction temperature drops
below 120^oC.
The AME8848 switches from voltage mode to current
mode when the load exceeds the rated output current.
This prevents over-stress. The AME8848 also incorpo-
rates current foldback to reduce power dissipation when
the output is short circuited. This feature becomes active
when the output drops below 0.8 volts, and reduces the
current flow by 65%. Full current is restored when the
voltage exceeds 0.8 volts.
1A CMOS LDO
n External Capacitors
The AME8848 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.
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Rev.A.04