Datasheet

TLE6251D
Fail Safe Functions
Data Sheet 12 Rev. 1.0, 2012-07-27
5.4 Undervoltage Detection
The HS CAN Transceiver TLE6251D is provided with undervoltage detection on the power supply V
CC
and the
power supply
V
IO
. Both undervoltage detection monitors are active in normal-operating mode. In stand-by mode
only the
V
IO
undervoltage monitoring is active, the V
CC
undervoltage monitoring is disabled.
In case the power supply
V
CC
or V
IO
drops below a voltage level where the transceiver TLE6251D cannot securely
send data to the bus or receive data from the bus, the undervoltage detection disables the data communication
(see Figure 7).
The transmitter and the receiver are disabled, but the bus biasing remains connected to
V
CC
/2. With a falling V
CC
supply, the “recessive” level of the CAN bus signal decreases respectively.
Figure 7 Undervoltage detection on
V
CC
or V
IO
Supply voltage V
CC
normal-operating
mode
communication blocked
normal-operating
mode
1)
STB=0
1)
Assuming the logical signal on the pin STB keeps its value during the undervoltage
event. In this case STB remains „low“.
delay time undervoltage
t
Delay(UV)
communication blocked
hysteresis
V
CC(UV,H)
Supply voltage V
IO
STB=0
delay time undervoltage
t
Delay(UV)
normal-operating
mode
normal-operating
mode
1)
V
CC
undervoltage
monitor
V
CC(UV)
V
IO
undervoltage
monitor
V
IO(UV)
hysteresis
V
IO(UV,H)