LND5201
1 A Low Dropout Positive Voltage Regulator
2.5 V, 1 A Regulator
DATA SHEET
GENERAL DESCRIPTION
Adjustable or fixed Output
Output Current of 1A
Low Dropout, 700mV at 1A Output
Current
0.04%
Line
Regulation
0.1% Load Regulation
100% Thermal Limit Burn-In
Fast Transient Response
Remote
Sense
FEATURES
The LND5201 series of positive adjustable and
fixed regulators are designed to provide 1A 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 LND5201 can also be used as
a single supply device (3-pin version). On-chip
trimming adjusts the reference voltage to 1%.
High efficiency Linear Regulators
Post Regulators for Switching
Supplies
Adjustable Power Supply
TYPICAL APPLICATION DATA
APPLICATIONS
LND5201
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
Vpower
Vcontrol
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
LND5201
Adj.
LND5201-1.5
1.5V
LND5201-2.5
2.5V
LND5201-2.85
2.85V
LND5201-3.0
3.0V
LND5201-3.3
3.3V
LND5201-3.5
3.5V
LND5201-5.0
5.0V
Note 1: Other fixed versions are available V
out
=1.5v to 5.0V
Absolute Maximum
Rating
Device Selection Guide (note 1)
LND5201
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
LND5201
PARAMETER
DEVICE
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Reference Voltage
LND5201
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
1A
*
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 1A
*
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 1A
*
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 1A
*
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 1A
*
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 to1A
*
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 1A
*
3.465
3.445
3.500
3.500
3.535
3.555
V
Output Voltage
LND5201-1.5
LND5201-2.5
LND5201-2.85
LND5201-3.0
LND5201-3.3
LND5201-3.5
LND5201-5.0
V
Control
=7.5V, V
Power
=5.5V
V
Control
=6.5V V
Power
=5.8V, I
Load
=0mA
to 1 A
*
4.950
4.920
5.000
5.000
5.050
5.080
V
Line Regulation
All
I
Load
=10mA, (1.5V+V
out
)
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,
I
Load
=10mA to 1A
*
0.08
0.40
%
Minimum Load
Current(Note 2)
LND5201
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 1A
*
20
mA
Ground Pin Current
LND5201-1.5/-
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
=10mAto 1A
*
5
10
mA
Adjust Pin Current
LND5201
V
Control
=2.75V, V
Power
=2.05V
I
Load
=10mA
*
50
120
A
Current Limit
All
(V
in
-V
out
)=3V
*
1000
1500
mA
Ripple Rejection
All
V
Control
= V
Power
=Vout+2.5V,
V
ripple
=1Vp.p, I
Load
=500mA
60
75
dB
Thermal Regulation
LND5201
TA=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
+0.8V I
Load
=1A
*
1.00
1.15
1.15
1.30
V
Power Input
(V
power
-V
out
)
All
V
Control
= V
out
+2.5V, I
Load
=1A
*
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 LND5201 (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 LND5201 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.
LND 5201
BLOCK DIAGRAM
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
APPLICATIONS INFORMATION
The LND5201 series of adjustable and fixed
regulators are designed to power the new
generation of microprocessors. The LND5201 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 LND5201 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 1A, the typical load
regulation is 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 LND5201 include
3.3V to 2.5V conversion with a 5V control
supply, 5V to 4.2V conversion with a 12V
control supply. The device is fully protected
against overcurrent and overtemperature
conditions.
Grounding and Output Sensing
The LND5201 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
convential 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 LND5201 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 LND5201 series
requires the use of an output capacitor as part
of the device frequency compensation. The
addition of 150
F aluminnum electrolytic or a
22
F solid tantalum on the output will ensure
stability for all operating conditions
LND5201
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
PDF 
ZIP