LP2975
MOSFET LDO Driver/Controller
General Description
A high-current LDO regulator is simple to design with the
LP2975 LDO Controller. Using an external P-FET, the
LP2975 will deliver an ultra low dropout regulator with ex-
tremely low quiescent current.
High open loop gain assures excellent regulation and ripple
rejection performance.
The trimmed internal bandgap reference provides precise
output voltage over the entire operating temperature range.
Dropout voltage is "user selectable" by sizing the external
FET: the minimum input-output voltage required for opera-
tion is the maximum load current multiplied by the R
DS
(ON)
of the FET.
Overcurrent protection of the external FET is easily imple-
mented by placing a sense resistor in series with V
IN
. The
57 mV detection threshold of the current sense circuitry mini-
mizes dropout voltage and power dissipation in the resistor.
The standard product versions available provide output volt-
ages of 12V, 5V, or 3.3V with guaranteed 25C accuracy of
1.5% ("A" grade) and 2.5% (standard grade).
Features
n
Simple to use, few external components
n
Ultra-small mini SO-8 package
n
1.5% (A grade) precision output voltage
n
Low-power shutdown input
n
<
1 A in shutdown
n
Low operating current (180 A typical
@
V
IN
= 5V)
n
Wide supply voltage range (1.8V to 24V)
n
Built-in current limit amplifier
n
Overtemperature protection
n
12V, 5V, and 3.3V standard output voltages
n
Can be programmed using external divider
n
-40C to +125C junction temperature range
Applications
n
High-current 5V to 3.3V regulator
n
Post regulator for switching converter
n
Current-limited switch
Block Diagram
Connection Diagram
DS100034-1
*R
SET
values are: 208k for 12V part, 72.8k for 5V part, and 39.9k for 3.3V
part.
Surface Mount Mini SO-8 Package
DS100034-2
Top View
For Order Numbers
See
Table 1 of this Document
See NS Package Number MUA08A
September 1997
LP2975
MOSFET
LDO
Driver/Controller
1999 National Semiconductor Corporation
DS100034
www.national.com
Ordering Information
TABLE 1. Package Marking and Ordering Information
Output Voltage
Grade
Order Information
Package Marking
Supplied As:
12
A
LP2975AIMMX-12
L47A
3.5k Units on Tape and Reel
12
A
LP2975AIMM-12
L47A
250 Units on Tape and Reel
12
STD
LP2975IMMX-12
L47B
3.5k Units on Tape and Reel
12
STD
LP2975IMM-12
L47B
250 Units on Tape and Reel
5.0
A
LP2975AIMMX-5.0
L46A
3.5k Units on Tape and Reel
5.0
A
LP2975AIMM-5.0
L46A
250 Units on Tape and Reel
5.0
STD
LP2975IMMX-5.0
L46B
3.5k Units on Tape and Reel
5.0
STD
LP2975IMM-5.0
L46B
250 Units on Tape and Reel
3.3
A
LP2975AIMMX-3.3
L45A
3.5k Units on Tape and Reel
3.3
A
LP2975AIMM-3.3
L45A
250 Units on Tape and Reel
3.3
STD
LP2975IMMX-3.3
L45B
3.5k Units on Tape and Reel
3.3
STD
LP2975IMM-3.3
L45B
250 Units on Tape and Reel
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2
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
-65C to +150C
Operating Junction Temperature
Range
-40C to +125C
Lead Temp. (Soldering, 5 seconds)
260C
ESD Rating
2 kV
Power Dissipation
(Note 2)
Internally Limited
Input Supply Voltage (Survival)
-0.3V to +26V
Input Supply Voltage (Operating)
+1.8V to +24V
Current Limit Pins (Survival)
-0.3V to +V
IN
Comp Pin (Survival)
-0.3V to +2V
Gate Pin (Survival)
-0.3V to +V
IN
ON/OFF Pin (Survival)
-0.3V to +20V
Feedback Pin (Survival)
-0.3V to +24V
Electrical Characteristics
Limits in standard typeface are for T
J
= 25C, and limits in boldface type apply over the full operating temperature range. Un-
less otherwise specified; V
ON/OFF
= 1.5V, V
IN
= 15V.
Symbol
Parameter
Conditions
Typ
LM2975AI-X.X
(Note 3)
LM2975I-X.X
(Note 3)
Units
Min
Max
Min
Max
V
REG
Regulation Voltage
(12V Versions)
12.5
<
V
IN
<
24V
12.0
11.820
12.180
11.700
12.300
V
(V
IN
- 0.5V)
>
V
GATE
>
(V
IN
- 5V)
11.640
12.360
11.520
12.480
Regulation Voltage
(5V Versions)
5.5
<
V
IN
<
24V
5.0
4.925
5.075
4.875
5.125
(V
IN
- 0.5V)
>
V
GATE
>
(V
IN
- 4.5V)
4.850
5.150
4.800
5.200
Regulation Voltage
(3.3V Versions)
3.8
<
V
IN
<
24V
3.3
3.250
3.350
3.217
3.383
(V
IN
- 0.5V)
>
V
GATE
>
(V
IN
- 3.3V)
3.201
3.399
3.168
3.432
V
COMP
Comp Pin Voltage
V
REG
<
V
IN
<
24V
1.240
1.215
1.265
1.203
1.277
V
1.209
1.271
1.196
1.284
I
Q
Quiescent Current
V
IN
= 5V
180
240
240
A
320
320
V
ON/OFF
= 0V
0.01
1
1
V
CL
Current Limit
Sense Voltage
V
IN
= 15V
V
FB
= 0.9 X V
REG
57
45
69
45
69
mV
39
72
39
72
V
ON/OFF
ON/OFF Threshold
Output = ON
0.94
1.10
1.10
V
1.20
1.20
Output = OFF
0.87
0.70
0.70
0.40
0.40
I
ON/OFF
ON/OFF
Input Bias Current
V
ON/OFF
= 1.5V
34
50
50
A
75
75
I
G
Gate Drive Current (Sourcing)
V
G
= 7.5V
V
FB
= 1.1 X V
REG
3.5
1.3
1.3
mA
0.3
0.3
Gate Drive Current (Sinking)
V
G
= 7.5V
V
FB
= 0.9 X V
REG
1100
350
350
A
40
40
V
G(MIN)
Gate Clamp Voltage
V
IN
= 24V
V
FB
= 0.9 X V
REG
17
15
19
15
19
V
R(V
IN
-G)
Resistance from
Gate to V
IN
V
IN
= 24V
V
ON/OFF
= 0
500
k
Open Loop
Voltage Gain
V
IN
= 15V
0.5V
V
GATE
13
5000
V/V
Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the de-
vice outside of its rated operating conditions.
Note 2: The LP2975 has internal thermal shutdown which activates at a die temperature of about 150C. It should be noted that the power dissipated within the
LP2975 is low enough that this protection circuit should never activate due to self-heating, even at elevated ambient temperatures.
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3
Electrical Characteristics
(Continued)
Note 3: Limits are 100% production tested at 25C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control
(SQC) methods. The limits are used to calculate National's Average Outgoing Quality Level (AOQL).
Typical Application Circuits
5V - 3.3V
@
5A LDO Regulator
DS100034-3
*See Application Hints.
**If current limiting is not required, short out this resistor.
Adjustable Voltage 5A LDO Regulator
DS100034-4
*See Application Hints.
***If current limiting is not required, short out this resistor.
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4
Typical Performance Characteristics
Unless otherwise specified: T
A
= 25C, C
IN
= 1 F, ON/OFF pin
is tied to 1.5V.
Minimum Operating Voltage
DS100034-5
V
IN
Referred Gate Clamp Voltage
DS100034-6
ON/OFF Threshold
DS100034-7
Current Limit Sense Voltage
DS100034-8
ON/OFF Pin Current
DS100034-9
Supply Current
DS100034-10
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