AZ809A_10 Datasheet, PDF (9/11 Pages) BCD Semiconductor Manufacturing Limited – 3-PIN MICROPROCESSOR RESET CIRCUIT

Data Sheet
3-PIN MICROPROCESSOR RESET CIRCUIT
AZ809A
Application Information (Continued)
Negative Going V_CC Transient
The AZ809A is optimized to immune fast negative-
going transients or glitches on the V_CC line, and the
sensitivity depends on the duration of the transient and
the magnitude of the undershoot below the reset
threshold (reset comparator overdrive). Figure 13
shows the maximum pulse width of a negative-going
V_CC transient that will not cause a reset pulse. As the
magnitude of the transient increases (goes farther
below the reset threshold), the maximum allowable
pulse width decreases. Any combination of duration
and overdrive that lies under the curve will not
generate a reset signal, typically, a V_CC transient that
goes 100mV below the reset threshold and lasts about
20µs or less will not cause a reset pulse.
400
360
320
280
240
200
160
120
80
40
0
2
VCC
V_TH
Overdrive
Reset Occurs
above the Curve
Duration
10
100
1000
Reset Comparator Overdrive V -V (mV)
TH CC
A 0.1µF bypass capacitor mounted as close as possible
to the V_CC pin will provide additional transient
rejection.
Figure 13. Maximum Transient Duration NOT Causing
a Reset Pulse vs. Reset Comparator Overdrive
Typical Application
V_CC
VCC
AZ809A
RESET
GND
VCC
Microprocessor
RESET
GND
Oct. 2010 Rev. 1. 3
Figure 14. Typical Application of AZ809A
BCD Semiconductor Manufacturing Limited
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