AME8821 Datasheet, PDF (8/15 Pages) Analog Microelectronics – 250mA Hi-PSRR, Low-Quiescent LDO with In-Rush Current Control For USB Application

AME, Inc.
AME8821
250mA Hi-PSRR, Low-Quiescent LDO
with In-Rush Current Control
For USB Application
n Detail Description
The AME8821 family of CMOS regulators contain a
PMOS pass transistor, voltage reference, error ampli-
fier, over-current protection, and thermal shutdown func-
tion.
The P-channel pass transistor receives data from
the error amplifier, over-current limit, and thermal pro-
tection 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
150^oC, or the current exceeds about 350mA. During
thermal shutdown, the output voltage remains low.
Normal operation is restored when the junction tem-
perature drops below 130^oC.
The AME8821 switches from voltage mode to cur-
rent mode when the load exceeds the rated output
current. This prevents over-stress.
n External Capacitors
The AME8821 is stable with an output capacitor to
ground of 4.7µF or greater. Ceramic capacitors have
the lower ESR, and will offer the best AC performance.
Conversely, Aluminum Electrolytic capacitors exhibit
the higher ESR, resulting in the poor 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 overall
cost.
A second capacitor is recommended between the
input and ground to stabilize V_IN. The input capacitor
should be at least 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
n Enable
The Enable pin is optional. EN for active high en-
able, ENB for active low enable. When disable the
Enable Pin EN = 0, ENB = V_IN, the PMOS pass tran-
sistor shuts off, and all internal circuits are powered
down. In this state, the standby current is less than
1µA.
8
Rev.A.01