Texas Instruments TPS3801, Application Report

Page: 6 / 28

Circuit Description
2 SLVA075
The reliability of a computer system is very important, several features are offered
to prevent errors: power-fail interrupts can signal dangerous conditions in time,
a battery back-up can protect the content of the memory, and so on. In smaller
systems this may be too expensive, and, in most applications, it is not required.
It is usually sufficient to force the microcomputer into a defined state after a
serious voltage drop.
To implement these functions while preventing problems, the following circuit
features are required:
•
Accurate detection of a voltage drop below the critical voltage
•
Generation of a reset signal when the supply voltage is below the device
specific threshold voltage
•
Keeping the reset signal active for a defined time after the supply voltage has
returned to its nominal value to ensure proper initialization of the
microprocessor or DSP
The Texas Instruments TPS3801 and TPS3809 families of integrated circuits
fulfill the requirements described above without requiring additional external
components.
2 Circuit Description
This section describes the TPS3801 and TPS3809 devices and features.
2.1 Overview of Features
Figure 2 is an overview of the features of TPS3801 and TPS3809.
TPS3801 TPS3809
Manual Reset
Function
Voltage
Supervision
Low-Active
Reset
Figure 2. Features Overview
2.2 Supervised Supply Voltages
Table 1 gives an overview of the nominal supply voltages, which can be
supervised by the TPS3801 and TPS3809. The values in the column of threshold
voltage are the negative-going threshold voltages. The differences between
positive-going and negative-going threshold voltage is explained in Chapter 3.