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AN1790 - APPLICATION NOTE

circuit. In most applications this is not a problem, as most microprocessors do not operate below 1V. How-

ever, in applications where RST must be valid down to 0V, a pull-down resistor should be added to hold

the RST output Low. The value of the resistor must be large enough not to load the RST output, and still

be small enough to pull the output to ground. The recommended value of the resistor is 100k

Ω(see Figure

8).

CONCLUSION

ST Reset Circuits are low-power supervisory devices, that have been specifically designed to monitor

power supplies in microprocessor systems.

In standard applications, they can be directly connected to the microprocessor, as no other external cir-

cuits are required. However, they can also be used in specific application environments, with the simple

addition of a resistor or capacitor.

They are available in small SOT23 and SOT143 packages; they require only a low supply current, typically

in the 5-10 µA range and offer a wide range of voltage thresholds.

REFERENCES

■

STM809, STM810, STM811, STM812

datasheet

REVISION HISTORY

Table 3. Document Revision History

Date

Version

Revision Details

04-Dec-2003

1.0

First Issue.

AI08636

RST

RESET

Input

R=100k

Ω