ATA5021 ATMEL, ATA5021 Datasheet - Page 5

• Manufacturer Part Number: ATA5021
• Description: Digital Window Watchdog Timer
• Manufacturer: ATMEL

3.3
3.4
Figure 3-1.
9145D–AUTO–05/10
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Supply Voltage Monitoring, Pin 5
Switch-over Mode Time, Pin 3
Reset out
Power-on Reset and Switch-over Mode
Mode
V
DD
Table 3-1.
The clock frequency determines all time periods of the logical part as shown in
trical Characteristics” on page 9
During ramp-up of the supply voltage and in the case of supply-voltage drops, the integrated
power-on reset (POR) circuitry sets the internal logic to a defined basic status and generates a
reset pulse at the reset output, pin 5. A hysteresis in the POR threshold prevents the circuit from
oscillating. During ramp-up of the supply voltage, the reset output stays active for a specified
period of time (t
on page
The switch-over mode time enables the synchronous operation of microcontroller and watchdog.
When the power-on reset time has elapsed, the watchdog has to be switched to monitoring
mode by the microcontroller by a “low” signal transmitted to the mode pin (pin 3) within the
time-out period, t
watchdog generates a reset pulse, t
chronized with the switch-over mode time, t
R1 (k )
100.00
100.00
100.00
100.00
100.00
119.50
119.50
119.50
119.50
119.50
81.20
81.20
81.20
81.20
5).
t
0
Comparison Table Clock Period Calculation versus Measurement on Test Board
0
) in order to bring the microcontroller into its defined reset status (see
C1 (nF)
1
10.49
10.49
10.49
0.47
1.04
4.75
0.23
0.47
1.04
4.75
0.23
0.47
1.04
4.75
. If the low signal does not occur within t1 (see
Period “T” (µs) by
New Formula
under the subheading “Timing”.
1253.21
1542.84
1843.26
136.32
595.56
167.76
733.17
200.37
875.90
63.47
40.07
78.07
47.81
93.20
6
, and t
t
1
1
1
, each time a reset pulse is generated.
starts again. Microcontroller and watchdog are syn-
Period “T” (µs) by
Measurement
1240.00
1530.00
1835.00
135.00
592.50
164.00
730.00
200.25
870.00
63.75
38.88
78.00
46.38
93.00
t
6
Figure 3-1 on page
Deviation of New
Formula versus
Measurement
Pin 6
Pin 5
Pin 3
ATA5021
Section 7. “Elec-
–2.1%
–1.7%
–1.7%
1.6%
1.9%
0.7%
1.3%
1.2%
0.9%
0.5%
0.8%
1.1%
0.5%
0.9%
Figure 3-1
5), the
5