LM2990S-12 National Semiconductor, LM2990S-12 Datasheet - Page 9

• Manufacturer Part Number: LM2990S-12
• Description: Linear Voltage Regulator IC
• Manufacturer: National Semiconductor

Specifications of LM2990S-12

• No. Of Pins: 3
• Output Current: 1.5A
• Termination Type: SMD
• Mounting Type: Through Hole
• Voltage Regulator Type: LDO Linear
• Peak Reflow Compatible (260 C): No
• Supply Voltage: 0.3V
• Current Rating: 1500A
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Application Hints
EXTERNAL CAPACITORS
The LM2990 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
regulator frequency response by the ESR could reduce the
phase margin, creating oscillations (refer to the graph on the
right). 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" from the input power supply filter.
FORCING THE OUTPUT POSITIVE
Due to an internal clamp circuit, the LM2990 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 LM2990 could damage
the device. The LM2990 output can also withstand fast
positive voltage transients up to 26V, without any current
limiting of the source. However, if the transients have a
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duration of over 1 ms, the output should be clamped with a
Schottky diode to ground.
Output Capacitor ESR
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