LX8221AIDU Microsemi Corporation, LX8221AIDU Datasheet - Page 5

• Manufacturer Part Number: LX8221AIDU
• Description: Dual 150ma CMOS Low Dropout Regulator
• Manufacturer: Microsemi Corporation

Copyright © 2000
Rev. 1.0a, 2005-03-03
tantalum or electrolytic capacitor with a minimum
recommended capacitance value of 1.0
between 5mΩ and 1Ω will satisfy the stability for the entire
operating range.
Optional Bypass Capacitor
The fixed/adjustable voltage version of the LX8221
includes a separate Bypass pin (CB1) for the fixed
regulator that allows for further reduction of output noise.
If the regulator’s output noise performance meets system
design specifications without the capacitor, omit it. The
bypass capacitor impacts the start up time, which is
inversely proportional to the size of bypass capacitor.
Further, the bypass capacitor reduces the regulator phase
margin. Hence, implementing the bypass capacitor will
require the use of a larger output capacitor to maintain the
be calculated using the following equation:
is negligible)
For the MSOP package, thermal resistance, θ
when mounted on a FR4 copper clad PCB. Junction
temperature of the integrated circuit can be calculated
using:
Where:
Example: Given the following conditions:
(Note: power dissipation resulting from quiescent current
TM
T
V
V
I
P
OUT
D
A
IN
OUT
=
= 60°C
= 4.2V
= 100mA
(
= 2.7V
V
IN
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
(
T
MAX
RISE
T
J
)
=
−
=
V
T
(
OUT
A
P
D
+
(
×
T
MIN
RISE
Θ
)
JA
)
×
)
I
OUT
(
MAX
Linfinity Microelectronics Division
µ
)
JA
F and ESR
is 220
A P P L I C A T I O N S
®
Microsemi
0
C/W
Dual 150mA CMOS Low Dropout Regulator
its output current.
Thermal Consideration
Thermal shutdown protects the integrated circuit from
thermal overload caused from a rise in junction temperature
during power dissipation. This type of protection is intended
for fault protection only and not as a means of current (or,
power) limiting during normal application usage. Proper
thermal evaluation should be done to ensure that the junction
temperature dose not exceed it’s maximum rating. Operating
at the maximum T
variation in individual device electrical characteristics and
thermal resistance, the built in thermal overload protection
may be activated at power levels slightly above or below the
rated dissipation. Power dissipation for each regulator can
calculate the total power dissipation and junction
temperature:
Total Power Dissipation:
Junction Temperature:
Layout Consideration:
The layout must be implemented with low impedance paths
for V
traces to avoid voltage drops and pick up noise. Adding an
area of PCB copper to the GND pin (pin 8) will reduce the
overall θ
substrate. This will lower the device junction temperature
improving overall output voltage accuracy. The input/output
capacitors must be placed as close as possible to each
voltage regulator output pin.
IN
, V
T
JA
J
OUT
=
since it is thermally connected to the device
P
P
60
RODUCTION
D
and Ground by creating sufficiently wide
=
o
C
(
J
4
of 150°C can impact reliability. Due to
2 .
+
V
(
. 0
−
15
2
7 .
W
D
V
×
ATA
)
×
220
0
1 .
S
o
A
C
HEET
=
/
W
. 0
15
)
=
W
93
o
C
LX8221
Page 5