AME, Inc.
1.5A CMOS LDO
AME8815
nDetailed Description
nExternal Capacitors
The AME8815 family of CMOS regulators contain a
PMOS pass transistor, voltage reference, error ampli-
fier, over-current protection, and thermal shutdown.
The AME8815 is stable with an output capacitor to
ground of 4.7µF or greater. Ceramic capacitors have the
lowest ESR, and will offer the best AC performance.
Conversely, Aluminum Electrolytic capacitors exhibit
the highest ESR, resulting in the poorest AC response.
Unfortunately, large value ceramic capacitors are com-
paratively expensive. One option is to parallel a 0.1µF
ceramic capacitor with a 10µF Aluminum Electrolytic.
The benefit is low ESR, high capacitance, and low over-
all cost.
The P-channel pass transistor receives data from the
error amplifier, over-current shutdown, and thermal pro-
tection circuits. During normal operation, the error am-
plifier compares the output voltage to a precision refer-
ence. Over-current and Thermal shutdown circuits be-
come active when the junction temperature exceeds
o
150 C, or the current exceeds 2.2A. During thermal shut-
down, the output voltage remains low. Normal operation
is restored when the junction temperature drops below
120 C.
A second capacitor is recommended between the input
and ground to stabilize Vin. The input capacitor should
be at least 0.1µF to have a beneficial effect.
o
The AME8815 behaves like a current source when the
load reaches 2.2A. However, if the load impedance
drops below 0.3 ohms, the current drops back to 600mA
to prevent excessive power dissipation. Normal op-
eration is restored when the load resistance exceeds
0.75 ohms.
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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AME [ ANALOG MICROELECTRONICS ]
