ATA6628 データシートの表示（PDF） - Atmel Corporation

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ATA6628

LIN Bus Transceiver with 3.3V (5V) Regulator and Watchdog

Atmel Corporation 

6.2 Worst Case Calculation with RWD_OSC = 51kΩ

The internal oscillator has a tolerance of 20%. This means that t1 and t2 can also vary by 20%. The worst case calculation for

the watchdog period twd is calculated as follows.

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 supply the trigger inputs correctly.

Table 6-1. Typical Watchdog Timings

RWD_OSC

kΩ

34

51

91

120

Oscillator

Period

tosc/µs

13.3

19.61

33.54

42.84

Lead

Time

td/ms

105

154.8

264.80

338.22

Closed

Window

t1/ms

14.0

20.64

35.32

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

20 ATA6628/ATA6630 [DATASHEET]

9117I–AUTO–10/14

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