SM72240 Datasheet, PDF (5/15 Pages) Texas Instruments – SM72240 SolarMagic 5-Pin Microprocessor Reset Circuit

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SM72240
SNIS154C – JANUARY 2011 – REVISED APRIL 2013
Typical Performance Characteristics (continued)
Low V_CC Characteristics
700
600
10 k: Pull-Up
Resistor
500
400
300
200
100
0
0.0
0.5
1.0
1.5
2.0
VCC (V)
Figure 9.
Timing Diagram
Figure 10.
CIRCUIT INFORMATION
RESET OUTPUT
The reset input of a µP initializes the device into a known state. The SM72240 microprocessor voltage
monitoring circuit asserts a forced reset output to prevent code execution errors during power-up, power-down,
and brownout conditions.
RESET is valid for V_CC ≥ 1V. Once V_CC exceeds the reset threshold, an internal timer maintains the output for
the reset timeout period. After this interval, reset goes high and the microprocessor initializes itself into a known
state. RESET is active low.
As V_CC drops below the reset threshold (such as during a brownout), the reset activates (see the NEGATIVE-
GOING V_CC TRANSIENTS section). When V_CC again rises above the reset threshold, the internal timer starts.
Reset holds until V_CC exceeds the reset threshold for longer than the reset timeout period. After this time, reset
releases.
Additionally, the Manual Reset input (MR) will initiate a forced reset. See the MANUAL RESET INPUT (MR)
section.
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