Datasheet

Power-OnResetRequirements
V
CC
Ramp-Up Re-Ramp-Up
Time to Re-Ramp
Time
Ramp-Down
t
FT
t
RT
t
RT
t
TRR_GND
V
CC
Ramp-Up
Time to Re-Ramp
Time
Ramp-Down
V
IN
drops below POR levels
t
RT
t
FT
t
TRR_VPOR50
TCA6408A
SCPS192C–APRIL2009–REVISEDJULY2009............................................................................................................................................................. www.ti.com
Intheeventofaglitchordatacorruption,TCA6408Acanberesettoitsdefaultconditionsbyusingthepower-on
resetfeature.Power-onresetrequiresthatthedevicegothroughapowercycletobecompletelyreset.This
resetalsohappenswhenthedeviceispoweredonforthefirsttimeinanapplication.
Thetwotypesofpower-onresetareshowninFigure17andFigure18.
Figure17.V
CC
isLoweredBelow0.2Vor0VandThenRampedUptoV
CC
Figure18.V
CC
isLoweredBelowthePORThreshold,ThenRampedBackUptoV
CC
Table2specifiestheperformanceofthepower-onresetfeatureforTCA6408Aforbothtypesofpower-onreset.
Table2.RECOMMENDEDSUPPLYSEQUENCINGANDRAMPRATESATT
A
=25°C
(1)
PARAMETERMINTYPMAXUNIT
t
FT
FallrateSeeFigure170.12000ms
t
RT
RiserateSeeFigure170.12000ms
t
RR_GND
Timetore-ramp(whenV
CC
dropstoGND)SeeFigure171µs
t
RR_POR50
Timetore-ramp(whenV
CC
dropstoV
POR_MIN
–50mV)SeeFigure181µs
LevelthatV
CCP
canglitchdownto,butnotcauseafunctional
V
CC_GH
SeeFigure191.2V
disruptionwhenV
CCX_GW
=1µs
Glitchwidththatwillnotcauseafunctionaldisruptionwhen
t
GW
SeeFigure1910µs
V
CCX_GH
=0.5×V
CCx
V
PORF
VoltagetrippointofPORonfallingV
CC
0.7V
V
PORR
VoltagetrippointofPORonfisingV
CC
1.4V
(1)Nottested.Specifiedbydesign.
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