Design Tips

Supply voltage Supervisor TL77xx Series

11

Figure 13. Buffered Circuit for the Reference Voltage

4. Design Tips

The application of the supply voltage supervisors of the series TL77xx is not complicated. However it

should be noticed, that this circuit is an analog circuit, whose function and performance - e.g. the stability

of the reference voltage - may be negatively influenced by noise in the neighboring circuits. Therefore the

voltage monitor should be placed on the printed circuit board, where there are no neighboring circuits in

the which switch high currents (like bus interface circuits and power switches). When laying out the layout

of the printed circuit board special care should taken with the interconnects which carry analog signals.

Beside the SENSE input these are the C

reduction of the output pulse width. Noise coupled into the V

may lead to undesired triggering of the circuit and by this to an undesired RESET pulse. Practice shows,

that this malfunction when high currents flow over the interconnects of these capacitors to the GND

terminal of the voltage monitor. To avoid these effects, the GND terminals of these capacitors must be

connected by the shortest way to the GND terminal of the voltage monitor in so that no currents caused by

other circuits flow over these wires. Figure14 show a layout proposal for the printed circuit board.

Furthermore the resistors of the voltage divider at the SENSE input of the TL7702 (R

have to be placed in so, that no noise may be coupled into this circuit.