LM2991MD8 [NSC]
IC VREG 3 V-24 V ADJUSTABLE NEGATIVE LDO REGULATOR, 1 V DROPOUT, UUC, DIE, Adjustable Negative Single Output LDO Regulator;
| 型号： | LM2991MD8 |
| 厂家： | 
National Semiconductor |
| 描述： | IC VREG 3 V-24 V ADJUSTABLE NEGATIVE LDO REGULATOR, 1 V DROPOUT, UUC, DIE, Adjustable Negative Single Output LDO Regulator 输出元件 调节器 |
| 文件： | 总12页 (文件大小：345K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
September 2000
LM2991
Negative Low Dropout Adjustable Regulator
General Description
Features
n Output voltage adjustable from −3V to −24V, typically
−2V to −25V
The LM2991 is a low dropout adjustable negative regulator
with a output voltage range between −3V to −24V. The
LM2991 provides up to 1A of load current and features a On
/Off pin for remote shutdown capability.
n Output current in excess of 1A
n Dropout voltage typically 0.6V at 1A load
n Low quiescent current
n Internal short circuit current limit
n Internal thermal shutdown with hysteresis
n TTL, CMOS compatible ON/OFF switch
n Functional complement to the LM2941 series
The LM2991 uses new circuit design techniques to provide a
low dropout voltage, low quiescent current and low tempera-
ture coefficient precision reference. The dropout voltage at
1A load current is typically 0.6V and
a guaranteed
worst-case maximum of 1V over the entire operating tem-
perature range. The quiescent current is typically 1 mA with
a 1A load current and an input-output voltage differential
greater than 3V. A unique circuit design of the internal bias
supply limits the quiescent current to only 9 mA (typical)
when the regulator is in the dropout mode (VOUT − VIN ≤ 3V).
Applications
n Post switcher regulator
n Local, on-card, regulation
n Battery operated equipment
The LM2991 is short-circuit proof, and thermal shutdown in-
cludes hysteresis to enhance the reliability of the device
when inadvertently overloaded for extended periods. The
LM2991 is available in 5-lead TO-220 and TO-263 packages
and is rated for operation over the automotive temperature
range of −40˚C to +125˚C. Mil-Aero versions are also avail-
able.
Typical Application
DS011260-1
V
= V
(1 + R2/R1)
OUT
REF
*Required if the regulator is located further than 6 inches from the power supply filter capacitors. A 1 µF solid tantalum or a 10 µF aluminum electrolytic
capacitor is recommended.
*
*Required for stability. Must be at least a 10 µF aluminum electrolytic or a 1 µF solid tantalum to maintain stability. May be increased without bound to
maintain regulation during transients. Locate the capacitor as close as possible to the regulator. The equivalent series resistance (ESR) is critical, and
should be less than 10Ω over the same operating temperature range as the regulator.
© 2000 National Semiconductor Corporation
DS011260
www.national.com
Connection Diagrams and Ordering Information
5-Lead TO-220
Straight Leads
5-Lead TO-220
Bent, Staggered Leads
DS011260-9
DS011260-2
Front View
Order Number LM2991T
See NS Package Number T05A
Front View
Order Number LM2991T Flow LB03
See NS Package Number T05D
TO263
5-Lead Surface-Mount Package
DS011260-11
Top View
DS011260-12
Side View
Order Number LM2991S
See NS Package Number TS5B
16-Lead Ceramic Dual-in-Line Package
16-Lead Ceramic Surface-Mount Package
DS011260-29
DS011260-30
Top View
Order Number LM2991J-QMLV
5962-9650501VEA
Order Number LM2991J-QML
5962-9650501QEA
Top View
Order Number LM2991WG-QML
5962-9650501QXA
See NS Package Number WG16A
See NS Package Number J16A
www.national.com
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
−65˚C to +150˚C
230˚C
Lead Temperature (Soldering, 10 sec.)
Operating Ratings (Note 1)
Input Voltage
−26V to +0.3V
2 kV
Junction Temperature Range (TJ)
−40˚C to +125˚C
−26V
ESD Susceptibility (Note 2)
Power Dissipation (Note 3)
Junction Temperature (TJmax
Maximum Input Voltage (Operational)
Internally limited
125˚C
)
Electrical Characteristics
VIN = −10V, VO = −3V, IO = 1A, CO = 47 µF, R1 = 2.7k, TJ = 25˚C, unless otherwise specified. Boldface limits apply over
the entire operating junction temperature range.
Parameter
Conditions
Typical
(Note 4)
−1.210
Min
Max
Units
Reference Voltage
5 mA ≤ IO ≤ 1A
−1.234
−1.186
V
V
5 mA ≤ IO ≤ 1A,
−1.27
−1.15
VO − 1V ≥ VIN ≥ −26V
Output Voltage
Range
−2
−25
−3
V
V
VIN = −26V
−24
Line Regulation
Load Regulation
Dropout Voltage
IO = 5 mA, VO − 1V ≥ VIN ≥ −26V
50 mA ≤ IO ≤ 1A
0.004
0.04
0.1
0.04
0.4
0.2
0.3
0.8
1
%/V
%
IO = 0.1A, ∆VO ≤ 100 mV
V
IO = 1A, ∆VO ≤ 100 mV
0.6
V
Quiescent Current
Dropout Quiescent
Current
IO ≤ 1A
0.7
16
5
mA
mA
VIN = VO, IO ≤ 1A
50
Ripple Rejection
Vripple = 1 Vrms, f
IO = 5 mA
= 1 kHz,
60
50
dB
ripple
Output Noise
ON /OFF Input
Voltage
10 Hz − 100 kHz, IO = 5 mA
(VOUT: ON)
200
1.2
1.3
0.1
40
450
µV
V
0.8
(VOUT: OFF)
2.4
ON /OFF Input
Current
VON/OFF = 0.8V (VOUT: ON)
VON/OFF = 2.4V (VOUT: OFF)
VIN = −26V, VON/OFF = 2.4V
VOUT = 0V
10
µA
µA
A
100
250
Output Leakage
Current
60
Current Limit
VOUT = 0V
2
1.5
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the deivce is in-
tended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: Human body model, 100 pF discharged through a 1.5 kΩ resistor.
Note 3: The maximum power dissipation is a function of T
, θ and T . The maximum allowable power dissipation at any ambient temperature is P = (T
A D Jmax
Jmax JA
− T )/θ . If this dissipation is exceeded, the die temperature will rise above 125˚C and the LM2991 will go into thermal shutdown. For the LM2991, the
A
JA
junction-to-ambient thermal resistance is 53˚C/W for the TO-220, 73˚C/W for the TO-263, and junction-to-case thermal resistance is 3˚C. If the TO-263 package is
used, the thermal resistance can be reduced by increasing the PC board copper area thermally connected to the package. Using 0.5 square inches of copper area,
θ
is 50˚C/W; with 1 square inch of copper area, θ is 37˚C/W; and with 1.6 or more square inches of copper area, θ is 32˚C/W.
JA JA
JA
Note 4: Typicals are at T = 25˚C and represent the most likely parametric norm.
J
3
www.national.com
Typical Performance Characteristics
Dropout Voltage
Normalized Output Voltage
Output Voltage
DS011260-13
DS011260-15
DS011260-18
DS011260-21
DS011260-24
DS011260-14
Output Noise Voltage
Line Transient Response
Ripple Rejection
Quiescent Current
Maximum Output Current
Maximum Output Current
ON /OFF Control Voltage
DS011260-17
DS011260-16
Load Transient Response
DS011260-19
DS011260-20
Output Impedance
DS011260-22
DS011260-23
www.national.com
4
Typical Performance Characteristics (Continued)
Adjust Pin Current
Low Voltage Behavior
Maximum Power
Dissipation (TO-220)
DS011260-26
DS011260-25
DS011260-27
Maximum Power Dissipation
(TO-263) (See Note 3)
DS011260-28
The lower stable ESR limit of 25 mΩ means that ceramic ca-
pacitors can not be used directly on the output of an LDO. A
ceramic (≥ 2.2 µF) can be used on the output if some exter-
nal resistance is placed in series with it (1Ω recommended).
Dielectric types X7R or X5R must be used if the temperature
Application Hints
External Capacitors
Like any low-dropout regulator, external capacitors are re-
qired to stabilize the control loop. These capacitors must be
correctly selected for proper performance.
±
range of the application varies more than 25˚ from ambient
to assure the amount of capacitance is sufficient.
INPUT CAPACITOR: An input capacitor is reqiuired if the
regulator is located more than 6″ from the input power supply
filter capacitor (or if no other input capaciotr is present).
CERAMIC BYPASS CAPACITORS:Many designers place
distributed ceramic capacitors whose value is in the range of
1000 pF to 0.1 µF at the power input pins of the IC’s across
a circuit board. These can cause reduced phase margin or
oscillations in LDO regulators.
A solid Tantalum or ceramic capacitor whose value is at least
1 µF is recommended, but an aluminum electrolytic (≥ 10 µF)
may be used. However, aluminum electrolytics should not be
used in applications where the ambient temperature can
drop below 0˚C because their internal impedance increases
significantly at cold temperatures.
The advent of multi-layer boards with dedicated power and
ground planes has removed the trace inductance that (previ-
ously) provided the necessary ″decoupling″ to shield the out-
put of the LDO from the effects of bypass capacitors.
OUTPUT CAPACITOR: The output capacitor must meet the
ESR limits shown in the graph, which means it must have an
ESR between about 25 mΩ and 10Ω.
These capacitors should be avoided if possible, and kept as
far far away from the LDO output as is practical.
A solid Tantalum (value ≥ 1 µF) is the best choice for the out-
put capacitor. An aluminum electrolytic (≥ 10 µF) may be
used if the ESR is in the stable range.
It should be noted that the ESR of a typical aluminum elec-
trolytic will increase by as much as 50X as the temperature
is reduced from 25˚C down to −40˚C, while a Tantalum will
exhibit an ESR increase of about 2X over the same range.
For this and other reasons, aluminum electrolytics should
not be used in applications where low operating tempera-
tures occur.
5
www.national.com
The output voltage of the LM2991 is set externally by a resis-
tor divider using the following equation:
Application Hints (Continued)
VOUT = VREF x (1 + R2/R1) − (IADJ x R2)
Output Capacitor ESR Range
where VREF = −1.21V. The output voltage can be pro-
grammed within the range of −3V to −24V, typically an even
greater range of −2V to −25V. The adjust pin current is about
60 nA, causing a slight error in the output voltage. However,
using resistors lower than 100 kΩ makes the adjust pin cur-
rent negligible. For example, neglecting the adjust pin cur-
rent, and setting R2 to 100 kΩ and VOUT to −5V, results in an
output voltage error of only 0.16%.
ON/OFF PIN
The LM2991 regulator can be turned off by applying a TTL or
CMOS level high signal to the ON/OFF pin (see Adjustable
Current Sink Application).
FORCING THE OUTPUT POSITIVE
Due to an internal clamp circuit, the LM2991 can withstand
positive voltages on its output. If the voltage source pulling
the output positive is DC, the current must be limited to 1.5A.
A current over 1.5A fed back into the LM2991 could damage
the device. The LM2991 output can also withstand fast posi-
tive voltage transients up to 26V, without any current limiting
of the source. However, if the transients have a duration of
over 1 ms, the output should be clamped with a Schottky di-
ode to ground.
DS011260-5
MINIMUM LOAD
A minimum load current of 500 µA is required for proper op-
eration. The external resistor divider can provide the mini-
mum load, with the resistor from the adjust pin to ground set
to 2.4 kΩ.
SETTING THE OUTPUT VOLTAGE
Typical Applications
Fully Isolated Post-Switcher Regulator
DS011260-6
www.national.com
6
Typical Applications (Continued)
Adjustable Current Sink
DS011260-10
7
www.national.com
Equivalent Schematic
www.national.com
8
Physical Dimensions inches (millimeters) unless otherwise noted
5-Lead T0-220, Straight Leads (T)
Order Number LM2991T
NS Package Number T05A
5-Lead T0-220, Bent, Staggered Leads (T)
Order Number LM2991T Flow LBO3
NS Package Number T05D
9
www.national.com
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
TO-263 5-Lead Plastic Surface Mount Package
Ordering Number LM2991S
NS Package Number TS5B
www.national.com
10
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
16-Lead Ceramic Dual-in-Line Package
Order Number LM2991J-QMLV
5962-9650501VEA
Order Number LM2991J-QML
5962-9650501QEA
NS Package Number J16A
11
www.national.com
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
16-Lead Ceramic Surface-Mount Package
Order Number LM2991WG-QML
5962-9650501QXA
NS Package Number WG16A
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
National Semiconductor
Corporation
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: support@nsc.com
National Semiconductor
Europe
National Semiconductor
Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
National Semiconductor
Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
Fax: +49 (0) 180-530 85 86
Email: europe.support@nsc.com
Deutsch Tel: +49 (0) 69 9508 6208
English Tel: +44 (0) 870 24 0 2171
Français Tel: +33 (0) 1 41 91 8790
Email: ap.support@nsc.com
www.national.com
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
相关型号：
LM2991MDS
IC VREG 3 V-24 V ADJUSTABLE NEGATIVE LDO REGULATOR, 1 V DROPOUT, UUC, DIE, Adjustable Negative Single Output LDO Regulator
NSC
©2020 ICPDF网 联系我们和版权申明