LM2991J-QML Datasheet PDF - National Semiconductor
| Part Number | LM2991J-QML | |
| Description | Negative Low Dropout Adjustable Regulator | |
| Manufacturers | National Semiconductor | |
| Logo |  |
|
|
There is a preview and LM2991J-QML download ( pdf file ) link at the bottom of this page. Total 11 Pages | ||
Preview 1 page No Preview Available !
May 1999
LM2991
Negative Low Dropout Adjustable Regulator
General Description
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.
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).
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.
Features
n Output voltage adjustable from −3V to −24V, typically
−2V to −25V
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
Applications
n Post switcher regulator
n Local, on-card, regulation
n Battery operated equipment
Typical Application
DS011260-1
VOUT = VREF (1 + R2/R1)
*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.
© 1999 National Semiconductor Corporation DS011260
www.national.com
|
| |
 
Typical Performance Characteristics (Continued)
Adjust Pin Current
Low Voltage Behavior
Maximum Power
Dissipation (TO-220)
DS011260-25
Maximum Power Dissipation
(TO-263) (See Note 3)
DS011260-26
DS011260-27
DS011260-28
Application Hints
EXTERNAL CAPACITORS
The LM2991 regulator requires an output capacitor to main-
tain stability. The capacitor must be at least 10 µF aluminum
electrolytic or 1 µF solid tantalum. The output capacitor’s
ESR must be less than 10Ω, or the zero added to the regu-
lator frequency response by the ESR could reduce the
phase margin, creating oscillations. The shaded area in the
Output Capacitor ESR graph indicates the recommended
ESR range. An input capacitor, of at least 1 µF solid tantalum
or 10 µF aluminum electrolytic, is also needed if the regulator
is situated more than 6 inches from the input power supply
filter.
Output Capacitor ESR Range
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
The output voltage of the LM2991 is set externally by a resis-
tor divider using the following equation:
VOUT = VREF x (1 + R2/R1) − (IADJ x R2)
where VREF = −1.21V. The output voltage can be pro-
grammed within the range of −3V to −24V, typically an even
5 www.national.com
Preview 5 Page |
Part DetailsOn this page, you can learn information such as the schematic, equivalent, pinout, replacement, circuit, and manual for LM2991J-QML electronic component. |
| Information | Total 11 Pages | |
| Link URL | [ Copy URL to Clipboard ] | |
| Download | [ LM2991J-QML.PDF Datasheet ] | |
Share Link :
Electronic Components Distributor
|
An electronic components distributor is a company that sources, stocks, and sells electronic components to manufacturers, engineers, and hobbyists. |
| SparkFun Electronics | Allied Electronics | DigiKey Electronics | Arrow Electronics |
| Mouser Electronics | Adafruit | Newark | Chip One Stop |
Featured Datasheets
| Part Number | Description | MFRS |
| LM2991J-QML | The function is Negative Low Dropout Adjustable Regulator. National Semiconductor | |
| LM2991J-QMLV | The function is Negative Low Dropout Adjustable Regulator. National Semiconductor | |
Semiconductors commonly used in industry:
1N4148 |
BAW56 |
1N5400 |
NE555 | | ||
Quick jump to:
LM29
1N4
2N2
2SA
2SC
74H
BC
HCF
IRF
KA | ||