LND5203
3 A Low Dropout Positive Voltage Regulator
2.5 V, 3A Regulator
DATA SHEET
GENERAL DESCRIPTION
Adjustable or fixed Output
Output Current of 3A
Low Dropout, 700mV at 3A Output
Current
0.04%
Line
Regulation
0.1% Load Regulation
100% Thermal Limit Burn-In
Fast Transient Response
Remote
Sense
FEATURES
The LND5203 series of positive adjustable and
fixed regulators are designed to provide 3A with
higher efficiency than currently available
devices. All internal circuitry are designed to
operate down to 700mV input to output
differential and the dropout voltage is fully
specified as a function of load current. Dropout
voltage of the device is 100mV at light loads and
rising to 700mV at maximum output current. A
second low current input is required to achieve
this dropout. The LND5203 can also be used as
a single supply device (3-pin version). On-chip
trimming adjusts the reference voltage to 1%.
APPLICATIONS
High efficiency Linear Regulators
Post Regulators for Switching
Supplies
Adjustable
Power
Supply
TYPICAL APPLICATION DATA
V
OUT
= V
REF
(I+R2/R1) +I
ADJ
R2
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
SYMBOL
PARAMETER
MAXIMUM
UNITS
P
d
Power Dissipation
Internally limited
W
V
in
Input Voltage
V
Power
V
Control
7
13
V
T
J
Operating Junction
Temperature range
Control Section
Power Transistor
0 to 125
0 to 150
C
T
STG
Storage Temperature
-65 to 150
C
T
LEAD
Lead Temperature (Soldering,
10 sec)
300
C
DEVICE
OUTPUT VOLTAGE
LND5203
Adj.
LND5203-1.5
1.5V
LND5203-2.5
2.5V
LND5203-2.85
2.85V
LND5203-3.0
3.0V
LND5203-3.3
3.3V
LND5203-3.5
3.5V
LND5203-5.0
5.0V
Note 1: Other fixed versions are available V
Out
=1.5v to 5.0V
Absolute Maximum
Rating
Device Selection Guide (note 1)
LND5203
Package Information
Vin
Vout
ADJ/GND
3 LEAD TO 220 (Front view)
5 LEAD TO 220 (Front View)
Vpower
Vcontrol
OUTPUT
ADJ/GND
SENSE
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
LND5203
PARAMETER
DEVICE
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Reference Voltage
LND5203
V
control
=2.75V, V
power
= 2V, I
Load
=
10mA
V
Control
=2.7V to 12 V
V
Power
=3.3V to 5.5V, I
Load
=10mA to
3A
*
1.238
1.230
1.250
1.250
1.262
1.270
V
V
Control
=4V, V
Power
=2V
V
Control
=3V, V
Power
=2.3V,I
Load
=0mA
to 3A
*
1.485
1.475
1.500
1.500
1.515
1.525
V
V
Control
=5V, V
Power
=3.3V
V
Control
=4V, V
Power
=3.3V I
Load
=0mA
to 3A
*
2.475
2.460
2.500
2.500
2.525
2.540
V
V
Control
=5.35V, V
Power
=3.35V
V
Control
=4.4V,V
Power
=3.7V, I
Load
=0mA to 3A
*
2.821
2.805
2.850
2.850
2.879
2.895
V
V
Control
=5.5V, V
Power
3.5V
V
Control
=4.5V, V
Power
3.8V, I
Load
=0mA
to 3A
*
2.970
2.950
3.000
3.000
3.030
3.050
V
V
Control
=5.8V, V
Power
=3.8V
V
Control
=4.8V, V
Power
= 4.1V, I
Load
=
0mA to 3A
*
3.267
3.247
3.300
3.300
3.333
3.353
V
V
Control
=6V,V
Power
=4V
V
Control
=5V, V
Power
=4.3V,I
Load
=0mA
to 3A
*
3.465
3.445
3.500
3.500
3.535
3.555
V
Output Voltage
LND5203-1.5
LND5203-2.5
LND5203-2.85
LND5203-3.0
LND5203-3.3
LND5203-3.5
LND5203-5.0
V
Control
=7.5V, V
Power
=5.5V
V
Control
=6.5V V
Power
=5.8V, I
Load
=0mA
to 3 A
*
4.950
4.920
5.000
5.000
5.050
5.080
V
Line Regulation
All
I
Load
=10mA, (1.5V+Vout) <= V
Control
<= 12V,0.8V <=(V
Power
-V
Out
) <=
5.5V
*
0.04
0.20
%
Load Regulation
All
V
Control
=V
Out
+2.5V,V
Power
=V
Out
+0.8V, Iload=10mA to 3A
*
0.08
0.40
%
Minimum Load
Current(Note 2)
LND5203
V
Control
=5V,V
Power
=3.3V, V
ADJ
=0V
*
1.7
5
mA
Control Pin Current(Note 3)
All
V
Control
=V
Out
+2.5V, V
Power
=V
Out
+0.8V,
I
Load
=10mA to 3A
*
60
mA
Ground Pin Current
LND5203-1.5/-
2.5/-2.85/-3.0/-
3.3/-3.5/-5.0
V
Control
=V
Out
+2.5, V
Power
=V
Out
+0.8V,
I
Load
=10mA to 3A
*
5
10
mA
Adjust Pin Current
LND5203
V
Control
=2.75V, V
Power
=2.05V
I
Load
=10mA
*
50
120
A
Current Limit
All
(V
In
-V
Out
)=3V
*
3
4
A
Ripple Rejection
All
V
Control
=V
Power
=V
Out
+2.5V,V
Ripple
=1Vp
.p, I
Load
=1.5A
60
75
dB
Thermal Regulation
LND5203
T
A
=25C,30ms pulse
0.003
%/W
Dropout Voltage Note 4
Control Input
All
V
Power
=V
Out
+0.8, I
Load
=10mA
V
Power
=V
Out
+0.8Vi
Load
=3A
*
1.00
1.15
1.15
1.30
V
Power Input
(V
Power
-V
Out
)
All
V
Control
=V
Out
+2.5V, I
Load
=3A
*
0.55
0.70
V
Electrical Characteristics
At I
load
= 0mA and T
J
=
25 C unless otherwise specified
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
The* denotes the specifications which apply over the full temperature range.
Note 1: Unless otherwise specified Vout=Vsense. For LND5203 (adj.) Vadj=0V
Note 2: For the adjustable device the minimum load current is the minimum current required to maintain regulation.
Normally the current in the resistor divider used to set the output voltage is selected to meet the minimum load current
requirement.
Note 3: The control pin current is the drive current required for the output transistor. This current will track output with
a ratio of about 1:100.
Note 4: The dropout voltage for the LND5203 is caused by either minimum control voltage or minimum power voltage.
The specifications represent the minimum input/output voltage required to maintain 1% regulation.
PIN FUNCTIONS (5-LEAD)
Sense (Pin 1): This pin is the positive
side of the reference voltage. With this
pin it is possible to Kelvin sense the
output voltage at the load.
Adjust (Pin 2): This pin is the negative
side of the reference voltage. Adding a
small bypass capacitor from the Adjust
pin to ground improves the transient
response. For fixed voltage devices the
Adjust pin is also brought out to allow
the user to add a bypass capacitor.
GND (Pin 2): For fixed voltage devices
this is the bottom of the resistor divider
that sets the output voltage.
V
power
(Pin 5): This pin is the
collector of the power transistor. The
output load current is supplied
through this pin. The voltage at this
pin must be 0.7V greater than the
output voltage for the device to
regulate.
V
control
(pin 4): This pin is the supply
pin for the control circuitry. The
current flow into this pin will be about
1% of the output current. The
voltage at this pin must be 1.3V
greater than the output voltage for
the device to regulate.
Output (Pin 3): This is the power
output of the device.
LND5203
BLOCK DIAGRAM
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
APPLICATION INFORMATION
The LND5203 series of adjustable and fixed
regulators are designed to power the new
generation of microprocessors. The LND5203 is
designed to make use of multiple power
supplies, present in most systems, to reduce the
dropout voltage. One of the advantages of the
two supply approach is maximizing the
efficiency.
The second supply is at least 1V greater than
output voltage and is providing the power for the
control circuitry and supplies the drive current to
the NPN output transistor. This allows the NPN
output transistor to be driven into saturation. For
the control voltage the current requirement is
small equal to about 1% of the output current.
This drive current becomes part of the output
current. The maximum voltage on the Control
pin is 12V. The maximum voltage at the Power
pin is 7V. By tying the control and power inputs
together the LND5203 can also be operated as
a single supply device. In single supply
operation the dropout will be determined by the
minimum control voltage.
Both fixed and adjustable versions have remote
sense pins, permitting very accurate regulation
of output voltage. As a result, over an output
current range of
100mA to 3A, the typical load regulation are less
than 1mV. For the fixed voltages the adjust pin
is brought out allowing the user to improve
transient response by bypassing the internal
resistor divider. Optimum transient response is
provided using a capacitor in the range of 0.1F
to 1F for bypassing the Adjust pin. In addition
to the enhancements mentioned, the reference
accuracy has been improved by a factor of two
with a guaranteed initial tolerance of 1% at
25C and 1.6% accuracy over the full
temperature and load current range.
Typical applications for the LND5203 include
3.3V to 2.5V conversion with a 5V control
supply, 5V to 4.2 V conversion with a 12V
control supply. The device is fully protected
against overcurrent and overtemperature
conditions.
Grounding and Output Sensing
The LND5203 allows true Kelvin sensing for
both the high and low side of the load. As a
result the voltage regulation at the load can
be easily optimized. Voltage drops due to
parasitic resistance's between the regulator
and the load can be placed inside the
regulation loop. The advantages of remote
sensing are illustrated in figures 1 through 3.
Figure 1 shows the device connected as a
conventional 3 terminal regulator with the
sense lead connected directly to the output of
the device. Rp is the parasitic resistance of
the connections between the device and the
load. Trace A of figure 3 illustrates the effect
of Rp.
Figure 2 shows the device connected to take
advantage of the remote sense feature. The
Sense pin and the top of the resistor divider
are connected to the top of the load. The
bottom of the resistor divider is connected to
the bottom of the load. The effect on output
regulation can be seen in trace B of figure 3.
It is important to note that the voltage drops
due to Rp are not eliminated; they will add to
the dropout voltage of the regulator
regardless. The LND5203 can control the
voltage at the load as long as the input-
output voltage is greater than the total of the
dropout voltage of the device plus the voltage
drop across Rp.
Stability
The circuit design used in the LND5203
series requires the use of an output capacitor
as part of the device frequency
compensation. The addition of 150
F
aluminum electrolytic or a 22
F solid
tantalum on the output will ensure stability for
all operating conditions
LND5203
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
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