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

effective capacitance to zero. To maintain regulator stability

down to −40˚C, capacitors rated at that temperature (such as

tantalums) must be used.

RESET OUTPUT

The range of values for the delay capacitor is limited only by

stray capacitances on the lower extreme and capacitance

leakage on the other. Thus, delay times from microseconds

to seconds are possible. The low charging current, typically

2.0 microamps, allows the use of small, inexpensive disc ca-

pacitors for the nominal range of 100 to 500 milliseconds.

This is the time required in many microprocessor systems for

the clock oscillator to stabilize when initially powered up. The

RESET output of the regulator will thus prevent erroneous

data and/or timing functions to occur during this part of op-

eration. The same delay is incorporated after any other fault

condition in the regulator output is corrected.

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