11.1 Layout Guidelines

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, take special care with the interconnects which carry analog signals. Beside the SENSE input these are the C_T and V_ref terminals. Noise coupled into the C_T input will lead to a reduction of the output pulse width. Noise coupled into the V_ref input or into the filter capacitor at this input 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. Figure 16 show a layout proposal for the printed circuit board. Furthermore the resistors of the voltage divider at the SENSE input of the TL7702 (R2 and R3 in Figure 16) have to be placed in so, that no noise may be coupled into this circuit.

11.2 Layout Example

Figure 16. Printed Circuit Layout for the Supply Voltage Supervisor