ATA6622 ATMEL Corporation, ATA6622 Datasheet - Page 16

• Manufacturer Part Number: ATA6622
• Description: LIN Bus Transceiver with 3.3V (5V) Regulator and Watchdog
• Manufacturer: ATMEL Corporation

6.2
16
Worst Case Calculation with R
ATA6622/ATA6624/ATA6626 [Preliminary]
Figure 6-1.
The internal oscillator has a tolerance of 20%. This means that t
The worst case calculation for the watchdog period t
The ideal watchdog time t
t
t
t
t
t
t
A microcontroller with an oscillator tolerance of ±15% is sufficient to supply the trigger inputs
correctly.
Table 6-1.
2
1,min
2,min
wdmax
wdmin
wd
NTRIG
.
R
NRES
VCC
3.3V
= 29.3 ms ±4.5 ms (±15%)
WD_OSC
120
kΩ
5V
34
51
91
= 0.8 × t
= 0.8 × t
= t
= t
1max
1min
Undervoltage Reset
t
reset
+ t
= 24.8 ms
Oscillator
1
2
Timing Sequence with R
= 17.3 ms, t
Typical Watchdog Timings
Period
t
= 16.5 ms, t
19.61
33.54
42.84
2min
osc
= 4 ms
13.3
/µs
= 16.5 ms + 17.3 ms = 33.8 ms
WD_OSC
264.80
338.22
t
154.8
wd
Lead
Time
1,max
2,max
d
105
/ms
is between the maximum t
= 51 kΩ
= 1.2 × t
= 1.2 × t
t
d
= 155 ms
Window
Closed
t
trig
45.11
t
20.64
35.32
14.0
1
/ms
> 200 ns
WD_OSC
1
2
t
1
= 24.8 ms
= 26 ms
= 20.6 ms
= 51 kΩ
Open Window
DRAFT
t
wd
t
21.67
37.06
47.34
14.7
wd
2
t
/ms
2
= 21 ms
is calculated as follows.
1
and the minimum t
t
Trigger Period from
1
1
Microcontroller
and t
t
29.32
50.14
64.05
wd
19.9
2
/ms
can also vary by 20%.
1
t
2
plus the minimum
4986B–AUTO–07/07
Watchdog Reset
t
nres
Reset Time
= 4 ms
t
nres
4
4
4
4
/ms