In many modern systems (or sub-systems),
multiple voltage rails are often needed (we refer to this as the power
tree). Often these power trees have tight voltage specification for reliable
operation. If these specifications are not satisfied, unreliable operation
or permanent malfunction can happen. To help enable reliable operation,
voltage rails are supervised in real time and corrective action (such as
power-down, disabling local regulators, etc.) is propagated trough the
system.
In this example, two voltage rails are monitored
using a window trigger to make sure the rails are operating within
specification. Detailed design procedure and component selection is provided
below. The design is summarized in
Figure 9-1.
Note: All calculated numbers shown in this
example are rounded to two decimal places with the exception of the
bottom resistor for the sense divider which is rounded to 3 decimal
places.