Regulated output voltage. Regulator stability is achieved with external capacitor of 1uF
Adjust pin. Connect a resistor divider to this pin to establish preferred output voltage.
BLOCK DIAGRAM
VIN1
EN1
EN2
VIN2
VOUT1
VOUT2
P
ACKAGE
D
ATA
P
ACKAGE
D
ATA
THERM AL
SENSOR
CURRENT
LIM IT
CURRENT
LIMIT
THERMAL
SENSOR
+
CB1
-
CONTROL
LOGIC
CONTROL
LOGIC
+
-
ADJ
VREF
VREF
GND
Copyright
2000
Rev. 1.0, 2002-01-02
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
LX8221
Dual 150mA CMOS Low Dropout Regulator
P
RODUCTION
RECOMMENDED OPERATING CONDITIONS
W W W.
Microsemi
.COM
Parameter
Input Operating Voltage Range (Note 1)
Enable Input Voltage Range
Continuous Output Current Range
Input Capacitor (V
IN
to GND)
Output Capacitor (V
OUT
to GND)
Symbol
VIN1, VIN2
EN1/2
I
OUT
1,
I
OUT
1
C
IN
C
OUT
Min
2.5
LX8221
Typ
Max
6
V
IN
+ 0.3V
Units
V
V
mA
µF
µF
150
1.0*
1.0*
2.2
Note 1: The minimum V
IN
has to meet two conditions V
IN
> 2.5V and V
IN
> V
OUT
+ V
DROPOUT
.
* Size your output capacitor to meet the transient loading requirement. If you have a very dynamic load, a lower ESR and larger value capacitor will improve the response to
these load steps.
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature -40°C
≤
T
A
≤
125°C except
where otherwise noted. Test conditions:
V
IN
= V
OUT
+ 0.5V; I
OUT
=10mA; C
IN
= 1
µ
F; C
OUT
= 1
µ
F; T
J
= T
A
using low duty cycle pulse
testing methods.
LX8221
Parameter
Symbol
Test Conditions
Units
Min
Typ
Max
Output Voltage (2.5, 2.7, 3.0, ADJ)
Adjust Reference Voltage
VOUT1/2
V
ADJ
V
RV
V
RI
T
J
= 25°C
0mA
≤
I
OUT1/2
≤
150mA, (V
OUT1/2
+ 0.5V)
≤
V
IN
≤
6V
T
J
= 25°C
0mA
≤
I
OUT1/2
≤
150mA, 2.85V
≤
V
IN
≤
6V
(V
OUT1/2
+ 0.5V)
≤
V
IN
≤
6V, I
OUT1/2
= 0.1mA
0.5mA
≤
I
OUT1/2
≤
100mA
I
LOAD1/2
= 1mA,
∆
VO
= -1%
I
LOAD1/2
= 50mA,
∆
VO
= -1%
I
LOAD1/2
= 100mA,
∆
VO
= -1%
I
LOAD1/2
= 150mA,
∆
VO
= -1%
EN1 = High, EN2 = High
EN1 = Low, EN2 = Low
V
ADJ
= 1.25V
V
EN1/2
= V
IN
2.0
0.4
VOUT1 = 0V, VOUT2 = 0V
T
J
= 25°C, f = 120Hz
T
J
= 25°C, C
OUT
= 10uF,C
BYPASS
= 470 pF
400
50
50
170
-1
-2.5
1.163
1.152
1
2.5
1.187
1.200
0.15
1.5
0.050
0.175
0.3
0.4
440
1
100
100
%
V
%/V
%V
NOM
1.175
0.04
∆
V
O
∆
V
IN
∆
V
O
Load Regulation
∆
I
O
Line Regulation
Dropout Voltage
(Note 2)
Ground Pin Current
Adjust Input Bias Current
Enable Pin Current
Enable Threshold
Short Circuit Current Limit
Power Supply Rejection Ratio
Output Noise
Thermal Shutdown Temperature
(
V
IN
−
V
O
)
V
DO
I
GND
I
STBY
I
ADJ
I
EN
V
EN(IH)
V
EN(IL)
I
OUT(SC)
PSRR
0.175
0.25
280
V
µA
nA
nA
V
mA
dB
µV
°C
e
N
T
SD
E
LECTRICALS
E
LECTRICALS
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.
Copyright
2000
Rev. 1.0, 2002-01-02
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
LX8221
Dual 150mA CMOS Low Dropout Regulator
P
RODUCTION
APPLICATIONS
W W W.
Microsemi
.COM
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
µ
F over the entire operating
temperature range. For the LX8221, a 1
µ
F ceramic type
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,
tantalum or electrolytic capacitor with a minimum
recommended capacitance value of 1.0
µ
F and ESR
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
LDO’s stability. The LX8221-x adjustable regulator’s
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:
R
V
OUT
=
V
ADJ
1
+
1
R
2
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
1
/
En
2
pins shuts the LX8221 off and reduces the supply
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
IN
.
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
0
C; there is
no appreciable thermal hysteresis.
Short Circuit Current Protection
The LX8221 includes over-current protection, when the
output load current exceeds about 400mA. When this
occurs, the protection circuit forces the regulator to decrease
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
J
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. Power dissipation for each regulator can
A
PPLICATION
A
PPLICATION
Copyright
2000
Rev. 1.0, 2002-01-02
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX8221
Dual 150mA CMOS Low Dropout Regulator
P
RODUCTION
APPLICATIONS
W W W.
Microsemi
.COM
be calculated using the following equation:
P
D
=
(
V
IN
(
MAX
)
−
V
OUT
(
MIN
)
)
×
I
OUT
(
MAX
)
calculate the
temperature:
total
power
dissipation
and
junction
Total Power Dissipation:
P
D
=
(
4.2V
−
2.7 V
)
×
0.1A
=
0.15 W
(Note: power dissipation resulting from quiescent current
is negligible)
For the MSOP package, thermal resistance,
θ
JA
is 220
0
C/W
when mounted on a FR4 copper clad PCB. Junction
temperature of the integrated circuit can be calculated
using:
T
J
=
T
A
+
T
RISE
Junction Temperature:
T
J
=
60
o
C
+
(
0.15
W
×
220
o
C
/
W
)
=
93
o
C
Layout Consideration:
The layout must be implemented with low impedance paths
for V
IN
, V
OUT
and Ground by creating sufficiently wide
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
JA
since it is thermally connected to the device
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.
Where:
T
RISE
=
(
P
D
× Θ
JA
)
Example:
Given the following conditions:
!
!
!
!
T
A
= 60°C
V
IN
= 4.2V
V
OUT
= 2.7V
I
OUT
= 100mA
A
PPLICATION
A
PPLICATION
Copyright
2000
Rev. 1.0, 2002-01-02
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
京公网安备 11010802033920号
EEWORLD
