LX8819 Microsemi Corporation, LX8819 Datasheet - Page 5

• Manufacturer Part Number: LX8819
• Description: Dual Channel 1a Low Dropout Regulator
• Manufacturer: Microsemi Corporation

Copyright © 2003
Revision 1.0a, 4/29/2005
D
Drop-Out) linear regulators in Microsemi’s S-PAK power
package which offer maximum power dissipation in a low
profile surface mount technology. The family includes a
combination of fixed and adjustable versions.
channel can supply up to one amp independently with a
regulator design optimized for system efficiency by
consuming minimal ground current and directing quiescent
current to the load.
I
an input bypass capacitor of at least 2.2µF is required.
Generally it is recommended that a 20µF ceramic/tantalum
or 22µF electrolytic capacitor be used.
O
connected between each voltage output and ground to
stabilize the internal control loop.
capacitors, with different capacitance values, tolerances,
temperature coefficients, and equivalent series resistance
are available for use with the LX8819. It is recommended
that a minimum of 4.7µF be used at each voltage output.
supply system under rapidly changing current load
conditions, designers generally use additional output
capacitors connected in parallel.
serves to minimize the effects of the parasitic resistance
(ESR) and inductance (ESL) that are present in all
capacitors.
capacitor ESR’s in the range of 50mΩ to 2Ω.
generally best to use the same type of capacitors for both
input and output bypassing.
A
between the adjust terminal and ground (See Figure 2). By
placing a resistor, R
constant current is caused to flow through R
through R
is very small and constant when compared with the current
through R
ignored.
M
proper output regulation.
specified at 0mA for the fixed output and 2mA for the
adjustable output regulator.
NPUT
ESCRIPTION
DJUSTABLE
UTPUT
INIMUM
The LX8819 is part of a family of Dual LDO (Low
To improve load transient response and noise rejection
The LX8819 regulator requires output capacitors
To ensure good transient response from the power
The LX8819 develops a 1.25V reference voltage
The LX8819 has a minimum load requirement for
TM
C
APACITOR
C
2
2
APACITOR
, it represents a small error and can usually be
L
to set the overall output voltage. Because I
OAD
The regulator has been tested stable with
O
UTPUT
R
EQUIREMENT
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
2
V
, between these two terminals, a
OLTAGE
This minimum current is
Such an arrangement
A P P L I C A T I O N I N F O R M A T I O N
Many types of
Integrated Products Division
1
and down
®
Microsemi
Each
It is
ADJ
Dual Channel 1A Low Dropout Regulator
T
junction temperature exceeds 140°C.
independent thermal shutdown capability.
absolute maximum rated conditions for extended periods
may affect device reliability (See Thermal Considerations
below).
C
output load current exceeds 1.4A (typical) the current limit
protection circuit forces the regulator to decrease the output
current in order to maintain safe levels.
T
integrated circuit from thermal overload caused from a rise
in junction temperature during excessive power dissipation
conditions. This means of protection is intended for fault
protection only and not as a means of current or power
limiting during normal application usage.
the junction temperature (T
rating. Continuous operation at the maximum T
can impact reliability.
characteristics and thermal resistance, the built in thermal
overload protection may be activated at power levels
slightly above or below the rated dissipation. Also, peak
output power should be considered for each individual
output.
calculated using the following equation:
current is negligible and ignored)
(Note: Power dissipation resulting from quiescent (ground)
P
EMPERATURE
HERMAL
URRENT
The thermal protection shuts the LX8819 down when the
The LX8819 includes over current protection. When the
Thermal shutdown protection circuitry protects the
Proper thermal evaluation should be done to ensure that
Total power dissipation for the regulator can be
D
Due to variation in individual device electrical
=
VOUT
(
V
V
IN
1
L
IN
C
(
=
MAX
IMIT
ONSIDERATIONS
V
REF
Figure 2 – Basic Regulator Circuit
)
P
−
⋅
⎛
⎜ ⎜
⎝
P
ROTECTION
1
V
LX8819
ROTECTION
+
D
OUT
R
R
ATA
1
2
⎞
⎟ ⎟
⎠
1 A
1
I
+
ADJ
)
I
⋅
ADJ
I
S
OUT
J
⋅
) does not exceed its maximum
HEET
R
ADJ
1
1
+
(
V
IN
V
VOUT2
VOUT1
(
REF
MAX
)
Each output has
−
R
R
1
V
2
OUT
Exposure to
J
LX8819
2
of 150°C
)
⋅
I
OUT
2
Page 5