LM2991 Datasheet, PDF (1/19 Pages) National Semiconductor (TI) – Negative Low Dropout Adjustable Regulator

LM2991
www.ti.com
SNVS099H – MAY 1999 – REVISED JUNE 2013
LM2991 Negative Low Dropout Adjustable Regulator
Check for Samples: LM2991
FEATURES
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•2 Output Voltage Adjustable from −3V to −24V,
Typically −2V to −25V
• Output Current in Excess of 1A
• Dropout Voltage Typically 0.6V at 1A Load
• Low Quiescent Current
• Internal Short Circuit Current Limit
• Internal Thermal Shutdown with Hysteresis
• TTL, CMOS Compatible ON/OFF Switch
• Functional Complement to the LM2941 Series
APPLICATIONS
• Post Switcher Regulator
• Local, On-Card, Regulation
• Battery Operated Equipment
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 temperature coefficient precision reference.
The dropout voltage at 1A load current is typically
0.6V and an ensured worst-case maximum of 1V
over the entire operating temperature 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
(V_OUT − V_IN ≤ 3V).
The LM2991 is short-circuit proof, and thermal
shutdown includes hysteresis to enhance the
reliability of the device when inadvertently overloaded
for extended periods. The LM2991 is available in 5-
lead TO-220 and DDPAK/TO-263 packages and is
rated for operation over the automotive temperature
range of −40°C to +125°C. Mil-Aero versions are also
available.
Typical Application
V_OUT = V_REF (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.
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PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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