LX8221GIDU Microsemi Corporation, LX8221GIDU Datasheet - Page 4

• Manufacturer Part Number: LX8221GIDU
• Description: Dual 150ma CMOS Low Dropout Regulator
• Manufacturer: Microsemi Corporation

Copyright © 2000
Rev. 1.0a, 2005-03-03
Description
The LX8221 family of LDO linear regulators is available
in a 10-pin MSOP Package and provides a cost effective
power management solution for battery driven applications.
The regulator family includes both fixed/adjustable and
adjustable/adjustable output voltage versions. The internal
PMOS power device provides low dropout regulation with
a fast line and load transient response. It also includes
internal current limiting and thermal shutdown circuitry. In
this section you will find information about capacitor,
thermal, and layout design considerations.
Input Capacitor
To improve load transient response and noise rejection a
bypass capacitor is recommended (but it is not required for
stability). There are no requirements for the ESR
(Equivalent Series Resistor) on the input capacitor, but
tolerance and temperature coefficient must be considered
when selecting this capacitor to ensure that the capacitor’s
value will be around 1
temperature range. For the LX8221, a 1
capacitor may be connected between both VIN1/2 and
ground.
Output Capacitor
The LX8221 uses an internal feedback loop to maintain a
constant output voltage. This feedback loop induces a
natural phase shift and the amount of phase shift
determines the loop’s stability. Therefore, like any low-
dropout regulator, an output capacitor with low ESR
(Equivalent Series Resistance) is required between VOUT
and GND to stabilize the internal control loop. A ceramic,
Note 2: Dropout voltage is defined as the input to output differential at which the output voltage drops 1% below the nominal value. Dropout voltage specification
applies only to output voltages greater than 2.8 V. For output voltages below 2.8 V, the dropout voltage is nothing but the input to output differential, since the
minimum input voltage is 2.8 V.
Adjust Input Bias Current
Enable Pin Current
Enable Threshold
Short Circuit Current Limit
Power Supply Rejection Ratio
Output Noise
Thermal Shutdown Temperature
TM
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
µ
F over the entire operating
I
V
V
OUT(SC)
PSRR
I
T
EN(IH)
I
EN(IL)
ADJ
e
EN
SD
N
µ
F ceramic type
Linfinity Microelectronics Division
T
T
V
V
VOUT1 = 0V, VOUT2 = 0V
J
J
ADJ
EN1/2
= 25°C, f = 120Hz
= 25°C, C
A P P L I C A T I O N S
= 1.25V
®
Microsemi
= V
IN
OUT
Dual 150mA CMOS Low Dropout Regulator
= 10uF,C
LDO’s stability.
output voltage can be externally set by connecting the ADJ
pin/s to an external resistor divider (See Figure 1 and 2).
The output voltage can be calculated using the formula:
Enable
The Enable pin allows the LX8221 to be independently
turned on and off. The Enable pins are compatible with
standard TTL-CMOS levels. A logic zero (0.4V) on the En
En
current to less than 1µA (typ). Pulling the Enable inputs high
(2.0V) causes normal operation to resume. If the Enable
feature is not used, this pin can be connected to V
Minimum Load Requirement
Although line regulation is improved with a minimum load
of 100µA, the LX8221 does not have a minimum load
current in order to maintain stability. This is an especially
important feature in certain applications.
Temperature Protection
The thermal protection shuts the LX8221 down when the
junction temperature exceeds approximately 150
no appreciable thermal hysteresis.
Short Circuit Current Protection
The LX8221 includes over-current protection, when the
output load current exceeds about 400mA.
occurs, the protection circuit forces the regulator to decrease
2
pins shuts the LX8221 off and reduces the supply
BYPASS
= 470 pF
P
RODUCTION
The LX8221-x adjustable regulator’s
V
OUT
=
V
D
ADJ
ATA
2.0
⎛
⎜ ⎜
⎝
1
+
S
R
R
HEET
1
2
⎞
⎟ ⎟
⎠
400
170
50
50
100
100
0.4
IN
0
When this
C; there is
LX8221
.
mA
nA
nA
dB
µV
°C
V
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