Summary

Supply voltage Supervisor TL77xx Series

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Figure 15. Series Resistor at the C

To a small degree this resistor influences the delay time t

neglected, because - when determining the length of the reset pulse - a large reserve is taken into

account.

When designing a supply voltage supervision circuit often an analysis of the noise on the supply lines is

required. The probes of the oscilloscope usually used for this kind of measurement mostly are not capable

of performing the measurements correctly. The main reason is the ground wire attached to the probe. This

wire often acts as an antenna which receives all the noise generated by the surrounding circuits. This

leads to a wrong display on the oscilloscope screen. More accurate results are found, when the signal to

be measured is taken via a 0.1

measurement. The other end of the capacitor is connected to a coaxcable, whose shield is connected by

the shortest path to the next ground reference point. The coaxcable leads to the input of the oscilloscope,

where the cable has to be terminated correctly to avoid line reflections.

5. Summary

Monitoring of the supply voltage is absolutely mandatory to guarantee a correct initialization of the circuit

and to detect undefined operating condition e.g. an undervoltage. This report shows several application

examples for the supply voltage supervisor circuits of the series TL77xxA. Owing their very accurate

threshold voltage, they can be easily designed into systems, replacing expensive discrete circuits .