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参数资料
| 型号： | LX8819-25CDT |
| 厂商： | MICROSEMI CORP |
| 元件分类： | Fixed/Adjustable Positive Multiple Output LDO Regulator |
| 英文描述： | DUAL OUTPUT, FIXED/ADJUSTABLE POSITIVE LDO REGULATOR, PSSO5 |
| 封装： | PLASTIC, TO-252, D-PAK, 5-PIN |
| 文件页数： | 5/9页 |
| 文件大小： | 305K |
| 代理商： | LX8819-25CDT |
LX8819
DATA SHEET
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
WWW
.Microse
m
i
.CO
M
Dual Channel 1A Low Dropout Regulator
Copyright
2003
Revision 1.0a, 4/29/2005
TM
APPLI CATI ON I N FORMATI O N
DESCRIPTION
The LX8819 is part of a family of Dual LDO (Low
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.
Each
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.
INPUT CAPACITOR
To improve load transient response and noise rejection
an input bypass capacitor of at least 2.2F is required.
Generally it is recommended that a 20F ceramic/tantalum
or 22F electrolytic capacitor be used.
OUTPUT CAPACITOR
The
LX8819
regulator
requires
output
capacitors
connected between each voltage output and ground to
stabilize the internal control loop.
Many types of
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 4.7F be used at each voltage output.
To ensure good transient response from the power
supply system under rapidly changing current load
conditions, designers generally use additional output
capacitors connected in parallel.
Such an arrangement
serves to minimize the effects of the parasitic resistance
(ESR) and inductance (ESL) that are present in all
capacitors.
The regulator has been tested stable with
capacitor ESR’s in the range of 50m
to 2.
It is
generally best to use the same type of capacitors for both
input and output bypassing.
ADJUSTABLE OUTPUT VOLTAGE
The LX8819 develops a 1.25V reference voltage
between the adjust terminal and ground (See Figure 2). By
placing a resistor, R2, between these two terminals, a
constant current is caused to flow through R1 and down
through R2 to set the overall output voltage. Because IADJ
is very small and constant when compared with the current
through R2, it represents a small error and can usually be
ignored.
MINIMUM LOAD REQUIREMENT
The LX8819 has a minimum load requirement for
proper output regulation.
This minimum current is
specified at 0mA for the fixed output and 2mA for the
adjustable output regulator.
R1
R2
V
IN
ADJ
VOUT1
V
REF
I
ADJ
1 A
VOUT2
1
ADJ
2
1
REF
R
I
R
1
V
1
VOUT
+
+
=
LX8819
Figure 2 –
Basic Regulator Circuit
TEMPERATURE PROTECTION
The thermal protection shuts the LX8819 down when the
junction temperature exceeds 140
°C.
Each output has
independent thermal shutdown capability.
Exposure to
absolute maximum rated conditions for extended periods
may affect device reliability (See Thermal Considerations
below).
CURRENT LIMIT PROTECTION
The LX8819 includes over current protection. When the
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.
THERMAL CONSIDERATIONS
Thermal shutdown protection circuitry protects the
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.
Proper thermal evaluation should be done to ensure that
the junction temperature (TJ) does not exceed its maximum
rating. Continuous operation at the maximum TJ of 150°C
can impact reliability.
Due
to
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. Also, peak
output power should be considered for each individual
output.
Total power dissipation for the regulator can be
calculated using the following equation:
(
)
(
)
2
OUT
2
OUT
)
MAX
(
IN
1
OUT
1
OUT
)
MAX
(
IN
D
I
V
I
V
P
+
=
(Note: Power dissipation resulting from quiescent (ground)
current is negligible and ignored)
AA
PP
LL
IICC
AA
TT
IIOO
NN
SS
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| LX8820 | 制造商:MICROSEMI 制造商全称:Microsemi Corporation 功能描述:3.3V/1.0A Ultra Low Dropout Regulator |
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