Philips Semiconductors
Product specification
High speed CAN transceiver
TJA1041A
UVNOM FLAG
that VI/O and VCC are present). The flag is cleared at
power-on, or when the UVNOM flag is set or the transceiver
enters normal mode.
UVNOM is the VCC and VI/O undervoltage detection flag.
The flag is set when the voltage on pin VCC drops below
VCC(sleep) for longer than tUV(VCC) or when the voltage on
WAKE-UP SOURCE FLAG
pin VI/O drops below VI/O(sleep) for longer than tUV(VI/O)
.
Wake-up source recognition is provided via the wake-up
source flag, which is set when the wake-up flag is set by a
local wake-up request via pin WAKE. The wake-up source
flag can only be set after the pwon flag is cleared.
In normal mode the wake-up source flag can be made
available on pin ERR. The flag is cleared at power-on or
when the transceiver leaves normal mode.
When the UVNOM flag is set, the transceiver will enter
sleep mode to save power and not disturb the bus. In sleep
mode the voltage regulators connected to pin INH are
disabled, avoiding the extra power consumption in case of
a short-circuit condition. After a waiting time (fixed by the
same timers used for setting UVNOM) any wake-up request
or setting of the pwon flag will clear UVNOM and the timers,
allowing the voltage regulators to be reactivated at least
until UVNOM is set again.
BUS FAILURE FLAG
The bus failure flag is set if the transceiver detects a bus
line short-circuit condition to VBAT, VCC or GND during four
consecutive dominant-recessive cycles on pin TXD, when
trying to drive the bus lines dominant. In normal mode the
bus failure flag can be made available on pin ERR. The
flag is cleared when the transceiver re-enters normal
mode.
UVBAT FLAG
UVBAT is the VBAT undervoltage detection flag. The flag is
set when the voltage on pin VBAT drops below VBAT(stb)
.
When UVBAT is set, the transceiver will try to enter standby
mode to save power and not disturb the bus. UVBAT is
cleared when the voltage on pin VBAT has recovered. The
transceiver will then return to the operating mode
determined by the logic state of pins STB and EN.
LOCAL FAILURE FLAG
In normal mode or pwon/listen-only mode the transceiver
can recognize five different local failures, and will combine
them into one local failure flag. The five local failures are:
TXD dominant clamping, RXD recessive clamping, a
TXD-to-RXD short circuit, bus dominant clamping, and
over-temperature. Nature and detection of these local
failures is described in Section “Local failures”.
In pwon/listen-only mode the local failure flag can be made
available on pin ERR. The flag is cleared when entering
normal mode or when RXD is dominant while TXD is
recessive, provided that all local failures are resolved.
PWON FLAG
Pwon is the VBAT power-on flag. This flag is set when the
voltage on pin VBAT has recovered after it dropped below
VBAT(pwon), particularly after the transceiver was
disconnected from the battery. By setting the pwon flag,
the UVNOM flag and timers are cleared and the transceiver
cannot enter sleep mode. This ensures that any voltage
regulator connected to pin INH is activated when the node
is reconnected to the battery. In pwon/listen-only mode the
pwon flag can be made available on pin ERR. The flag is
cleared when the transceiver enters normal mode.
Local failures
WAKE-UP FLAG
The TJA1041A can detect five different local failure
conditions. Any of these failures will set the local failure
flag, and in most cases the transmitter of the transceiver
will be disabled. The following sections give the details.
The wake-up flag is set when the transceiver detects a
local or a remote wake-up request. A local wake-up
request is detected when a logic state change on
pin WAKE remains stable for at least twake. A remote
wake-up request is detected after two bus dominant states
of at least tBUSdom (with each dominant state followed by a
recessive state of at least tBUSrec). The wake-up flag can
only be set in standby mode, go-to-sleep command mode
or sleep mode. Setting of the flag is blocked during the
UVNOM flag waiting time. By setting the wake-up flag, the
UVNOM flag and timers are cleared. The wake-up flag is
immediately available on pins ERR and RXD (provided
TXD DOMINANT CLAMPING DETECTION
A permanent LOW level on pin TXD (due to a hardware or
software application failure) would drive the CAN bus into
a permanent dominant state, blocking all network
communication. The TXD dominant time-out function
prevents such a network lock-up by disabling the
transmitter of the transceiver if pin TXD remains at a LOW
level for longer than the TXD dominant time-out tdom(TXD)
.
2004 Feb 20
9
NXP [ NXP ]
