LM2990T-5.2 National Semiconductor, LM2990T-5.2 Datasheet - Page 7

• Manufacturer Part Number: LM2990T-5.2
• Description: IC,VOLT REGULATOR,FIXED,-5.2V,BIPOLAR,SIP,3PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LM2990T-5.2

• Rohs Compliant: NO

Typical Applications
Post Regulator for an Isolated Switching Power Supply
DS010801-5
The LM2940 is a positive 1A low dropout regulator; refer to its datasheet for further information.
Fixed Current Sink
Adjustable Current Sink
DS010801-7
DS010801-10
Application Hints
EXTERNAL CAPACITORS
Output Capacitor ESR
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 10 , or the zero added to the regu-
lator 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 posi-
tive voltage transients up to 26V, without any current limiting
DS010801-9
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.
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