TLE6368_06 datasheet(14/59 Pages) INFINEON

14 / 59 page

TLE 6368 / SONIC

Data Sheet

Rev. 2.2, 2006-12-01

Figure 6 Window watchdog timing definition

Figure 6 shows some guidelines for designing the watchdog trigger timing taking the

oscillator deviation of different devices into account. Of importance (w.c.) is the

maximum of the closed window and the minimum of the open window in which the

trigger has to occur.

The length of the OW and CW can be modified by SPI command. If a change of the

window length is desired during the Watchdog function is operating please send the SPI

command with the new timing with a ’Watchdog trigger Bit’ D15=1.In this case the next

CW will directly start with the new length.

A minimum time gap of > 1/48 of the actual OW/CW time between a ’Watchdog disable’

and ’Watchdog enable’ SPI-command should be maintained. This allows the internal

Watchdog counters to be resetted. Thus after the enable command the Watchdog will

start properly with a full CW of the adjusted length.

ECW, w.c.= tCW (1+∆)

closed window

open window

CW=tCW

definition

OSC=fOSCmax

reset start delay time after window

watchdog timeout

reset delay time without trigger

reset duration time after window

watchdog time-out

SR = tOW/2

OW=tCW

WDR = tRES

OWmin

OSC=fOSCmin

definition

worst cases

EOW, w.c.= ( tCW+tOW )(1-∆)

Example with:

CW=128ms

∆=25% (oscillator deviation)

ECW, w.c. = 128(1.25) = 160ms

EOW, w.c

= (128+128)(0.75) = 192ms

owmin

= 32ms

(not the same scale)

EOW = end of open window

ECW

(not the same scale)

OWmin= tOW - ∆ * ( t OW + 2* t CW )

Minimum open window time:

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