AME8816 Datasheet, PDF (6/14 Pages) Analog Microelectronics – 1.5A CMOS LDO

AME, Inc.
AME8816
1.5A CMOS LDO
n Detailed Description
The AME8816 family of CMOS regulators contain a
PMOS pass transistor, voltage reference, error amplifier,
over-current protection, and thermal shutdown.
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
140^oC, or the current exceeds 2.2A. During thermal
shutdown, the output voltage remains low. Normal op-
eration is restored when the junction temperature drops
below 120^oC.
The AME8816 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.
n External Capacitors
The AME8816 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 comparatively expen-
sive. One option is to parallel a 0.1µF ceramic capacitor
with a 10µF Aluminum Electrolytic. The benefit is low
ESR, high capacitance, and low overall cost.
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.
A third capacitor can be connected between the BY-
PASS pin and GND. This capacitor can be a low cost
Polyester Film variety between the value of 0.001 ~
0.01µF. A larger capacitor improves the AC ripple re-
jection, but also makes the output come up slowly. This
"Soft" turn-on is desirable in some applications to limit
turn-on surges.
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.
n Enable
When pulled low, the PMOS pass transistor shuts off,
and all internal circuits are powered down. In this state,
the quiescent current is less than 1µA. This pin behaves
much like an electronic switch.
100Kohm resistor is necessary between V_EN source and
EN pin when V_EN is higher than V_IN.
Note: There is no internal pull-up for EN PIN.
n Adjustable Version
The adjustable version uses external feedback resistors
to generate an output voltage anywhere from 1.5V
to 5.0V. Vadj is trimmed to 1.242V and VOUT is given by
the equation:
VOUT = Vadj ( 1 + R1 / R2 )
Feedback resistors R1 and R2 should be high enough to
keep quiescent current low, but increasing R1 + R2
will reduce stability. In general, R1 and R2 in the 10’s of
kΩ will produce adequate stability, given reasonable lay-
out precautions. To improve stability characteristics, keep
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