ATA6617 데이터 시트보기 (PDF) - Atmel Corporation

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ATA6617

Microcontroller with LIN Transceiver, 5V Regulator and Watchdog

Atmel Corporation 

Figure 3-9. Timing Sequence with RWD_OSC = 51kΩ

VCC

NRES

Undervoltage Reset

treset = 4ms

NTRIG

td = 155ms

t1

t1 = 20.6ms

t2 = 21ms

twd

Watchdog Reset

tnres = 4ms

t2

3.6.2

ttrig > 200ns

Worst Case Calculation with RWD_OSC = 51 kΩ

The internal oscillator has a tolerance of 20%. This means that t1 and t2 can vary by 20%. The

worst case calculation for the watchdog period twd is calculated below.

The ideal watchdog time twd is between the maximum t1 and the minimum t1 plus the minimum

t2.

t1,min = 0.8 × t1 = 16.5ms, t1,max = 1.2 × t1 = 24.8ms

t2,min = 0.8 × t2 = 17.3ms, t2,max = 1.2 × t2 = 26ms

twdmax = t1min + t2min = 16.5ms + 17.3ms = 33.8ms

twdmin = t1max = 24.8ms

twd = 29.3ms ±4.5ms (±15%)

A microcontroller with an oscillator tolerance of ±15% is sufficient to correctly supply the trig-

ger inputs.

Table 3-2. Typical Watchdog Timings

RWD_OSC

kΩ

34

Oscillator

Period

tosc/µs

13.3

Lead

Time

td/ms

105

Closed

Window

t1/ms

14.0

51

19.61

154.8 20.64

91

33.54 264.80 35.32

120

42.84 338.22 45.11

Open Window

t2/ms

14.7

21.67

37.06

47.34

Trigger Period from

Microcontroller

twd/ms

19.9

29.32

50.14

64.05

Reset

Time

tnres/ms

4

4

4

4

18 Atmel ATA6616/ATA6617

9132D–AUTO–12/10

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