Rainbow Electronics ATA6625 - Manual (Page 9)

9
4957E–AUTO–10/07
ATA6623/ATA6625
Figure 4-5. LIN Wake-up Diagram from Sleep Mode
4.4 Fail-safe Mode
At system power-up the device automatically switches to Fail-safe mode. The voltage regulator
is switched on (V
CC
= 3.3V/5V/50 mA), (see Figure 6-1 on page 11 ). The NRES output switches
to low for t
res
= 4 ms and gives a reset to the microcontroller. LIN communication is switched off.
The IC stays in this mode until EN is switched to high, and changes then to the Normal mode. A
power down of V
Batt
(V
S
< 4V) during Silent- or Sleep mode switches the IC into the Fail-safe
mode after power up. A logic low at NRES switches the IC into Fail-safe mode directly.
4.5 Unpowered Mode
If you connect battery voltage to the application circuit, the voltage at the VS pin increases
according to the block capacitor (see
Figure 6-1 on page 11 ). After VS is higher than the VS
undervoltage threshold VS
th
, the IC mode changes from Unpowered mode to Fail-safe mode.
The VCC output voltage reaches its nominal value after t
VCC
. This time, t
VCC
, depends on the
VCC capacitor and the load.
NRES is low for the reset time delay t
Reset
; no mode change is possible during this time.
Regulator wake-up time
Off state
On state
Low
Fail-safe Mode Normal Mode
EN High
Microcontroller
start-up time delay
Reset
time
Low or floating
Low or floating NRES
EN
VCC
voltage
regulator
RXD
LIN bus
Bus wake-up filtering time
t
bus