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LP3856-ADJ 3A Fast Response Ultra Low Dropout Linear Regulators
September 2006
LP3856-ADJ
3A Fast Response Ultra Low Dropout Linear Regulators
General Description
The LP3856-ADJ fast ultra low-dropout linear regulators op-
erate from a +2.5V to +7.0V input supply. These ultra low
dropout linear regulators respond very quickly to step
changes in load, which makes them suitable for low voltage
microprocessor applications. The LP3856-ADJ is developed
on a CMOS process which allows low quiescent current
operation independent of output load current. This CMOS
process also allows the LP3856-ADJ to operate under ex-
tremely low dropout conditions.
Dropout Voltage:
Ultra low dropout voltage; typically 39mV
at 300mA load current and 390mV at 3A load current.
Ground Pin Current:
Typically 4mA at 3A load current.
Shutdown Mode:
Typically 10nA quiescent current when
the shutdown pin is pulled low.
Adjustable Output Voltage:
The output voltage may be
programmed via two external resistors.
Features
n
n
n
n
n
n
n
n
n
Ultra low dropout voltage
Stable with selected ceramic capacitors
Low ground pin current
Load regulation of 0.08%
10nA quiescent current in shutdown mode
Guaranteed output current of 3A DC
Available in TO-263 and TO-220 packages
Overtemperature/overcurrent protection
−40˚C to +125˚C junction temperature range
Applications
n
n
n
n
n
n
n
n
Microprocessor power supplies
GTL, GTL+, BTL, and SSTL bus terminators
Power supplies for DSPs
SCSI terminator
Post regulators
High efficiency linear regulators
Battery chargers
Other battery powered applications
Typical Application Circuit
20074234
**See Application Hints
© 2006 National Semiconductor Corporation
DS200742
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LP3856-ADJ
Connection Diagrams
20074205
20074206
Top View
TO220-5 Package
Bent, Staggered Leads
Top View
TO263-5 Package
Pin Description for TO220-5 and TO263-5 Packages
Pin #
Name
1
2
3
4
5
SD
V
IN
GND
V
OUT
ADJ
Shutdown
Input Supply
Ground
Output Voltage
Set Output Voltage
LP3856-ADJ
Function
Ordering Information
20074231
Package Type Designator is "T" for TO220 package, and "S" for TO263 package.
TABLE 1. Package Marking and Ordering Information
Output
Voltage
ADJ
ADJ
ADJ
Order Number
LP3856ES-ADJ
LP3856ESX-ADJ
LP3856ET-ADJ
Current
Description
3A
3A
3A
Package
Type
TO263-5
TO263-5
TO220-5
Package Marking
LP3856ES-ADJ
LP3856ES-ADJ
LP3856ET-ADJ
Supplied As:
Rail
Tape and Reel
Rail
www.national.com
2
LP3856-ADJ
Block Diagram
LP3856-ADJ
20074229
3
www.national.com
LP3856-ADJ
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Storage Temperature Range
Lead Temperature
(Soldering, 5 sec.)
ESD Rating (Note 3)
Power Dissipation (Note 2)
Input Supply Voltage (Survival)
Shutdown Input Voltage
(Survival)
Output Voltage (Survival), (Note
6), (Note 7)
260˚C
2 kV
Internally Limited
−0.3V to +7.5V
−0.3V to 7.5V
−0.3V to +6.0V
−65˚C to +150˚C
I
OUT
(Survival)
Short Circuit Protected
Operating Ratings
Input Supply Voltage (Operating),
(Note 10)
Shutdown Input Voltage
(Operating)
Maximum Operating Current (DC)
Operating Junction Temp. Range
2.5V to 7.0V
−0.3V to 7.0V
3A
−40˚C to +125˚C
Electrical Characteristics
LP3856-ADJ
Limits in standard typeface are for T
J
= 25˚C, and limits in
boldface type
apply over the
full operating temperature range.
Unless otherwise specified: V
IN
= V
O(NOM)
+ 1V, I
L
= 10 mA, C
OUT
= 10µF, V
SD
= 2V.
Symbol
Parameter
Conditions
Typ
(Note 4)
LP3856-ADJ
(Note 5)
Min
V
ADJ
I
ADJ
∆V
OL
∆V
O
/
∆I
OUT
Adjust Pin Voltage
Adjust Pin Input Current
Output Voltage Line
Regulation (Note 8)
Output Voltage Load
Regulation
(Note 8)
Dropout Voltage
(Note 9)
V
OUT
+1V
≤
V
IN
≤
7V
10 mA
≤
I
L
≤
3A
V
OUT
+1V
≤
V
IN
≤
7V
10 mA
≤
I
L
≤
3A
V
OUT
+1V
≤
V
IN
≤
7.0V
10 mA
≤
I
L
≤
3A
1.216
10
0.02
0.06
0.08
0.14
39
390
4
4
0.01
4.5
6
55
75
500
700
9
10
9
10
10
50
A
A
1.198
1.180
Max
1.234
1.253
100
V
nA
%
%
Units
V
IN
- V
OUT
I
L
= 300 mA
I
L
= 3A
I
L
= 300 mA
mV
I
GND
Ground Pin Current In
Normal Operation Mode
Ground Pin Current In
Shutdown Mode
Peak Output Current
Short Circuit Current
I
L
= 3A
V
SD
≤
0.3V
-40˚C
≤
T
J
≤
85˚C
V
O
≥
V
O(NOM)
- 4%
mA
I
GND
I
O(PK)
I
SC
µA
Short Circuit Protection
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