Application Hints

OUTPUT CAPACITORS

The LM2984 output capacitors are required for stability.

Without them, the regulator outputs will oscillate, sometimes

by many volts. Though the 10 µF shown are the minimum

recommended values, actual size and type may vary de-

pending upon the application load and temperature range.

Capacitor effective series resistance (ESR) also affects the

IC stability. Since ESR varies from one brand to the next,

some bench work may be required to determine the mini-

mum capacitor value to use in production. Worst case is usu-

ally determined at the minimum ambient temperature and

the maximum load expected.

Output capacitors can be increased in size to any desired

value above the minimum. One possible purpose of this

would be to maintain the output voltages during brief condi-

tions of negative input transients that might be characteristic

of a particular system.

Capacitors must also be rated at all ambient temperatures

expected in the system. Many aluminum type electrolytics

will freeze at temperatures less than −30˚C, reducing their

Ripple Rejection (V

DS011252-49

Ripple Rejection (V

DS011252-50

Ripple Rejection (V

DS011252-51

Output Voltage

DS011252-8

Device Dissipation vs

Ambient Temperature

DS011252-9

Output Capacitor ESR

(Standby Output, Pin 9)

DS011252-10

Output Capacitor ESR

(Buffer Output, Pin 10)

DS011252-11

Output Capacitor ESR

(Main Output, Pin 11)

DS011252-12

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