TJA1055
NXP Semiconductors
Enhanced fault-tolerant CAN transceiver
7.2 Low power modes
The transceiver provides three low power modes which can be entered and exited via
STB and EN (see Table 5 and Figure 3).
The sleep mode is the mode with the lowest power consumption. Pin INH is switched to
HIGH-impedance for deactivation of the external voltage regulator. Pin CANL is biased to
the battery voltage via pin RTL. Pins RXD and ERR will signal the wake-up interrupt even
in case VCC is not present.
The standby mode operates in the same way as the sleep mode but with a HIGH level on
pin INH.
The power-on standby mode is the same as the standby mode, however, in this mode the
battery power-on flag is shown on pin ERR instead of the wake-up interrupt signal. The
output on pin RXD will show the wake-up interrupt. This mode is only for reading out the
power-on flag.
Table 5.
Mode
Normal operating and low power modes
Pin STB Pin EN
Pin ERR
LOW
Pin RXD
LOW
Pin RTL
switched
to
HIGH
HIGH
[2][3]
[2][3]
Goto-sleep LOW
command
HIGH
wake-up
interrupt
signal[1]
wake-up
interrupt
signal[1]
VBAT
Sleep
LOW
LOW
HIGH
LOW[4]
LOW
Standby
Power-on
standby
LOW
VBAT
power-on
flag[5]
wake-up
interrupt
signal[1]
VBAT
Normal
operating
HIGH
HIGH
error flag no error
flag
dominant recessive VCC
received
data
received
data
[1] Wake-up interrupts are released when entering normal operating mode.
[2] For TJA1055T a diode is added in series with the high-side driver of ERR and RXD to prevent a reverse
current from ERR to VCC in the unpowered state.
[3] For TJA1055T/3, ERR and RXD are open-drain.
[4] In case the goto-sleep command was used before. When VCC drops, pin EN will become LOW, but due to
the fail-safe functionality this does not effect the internal functions.
[5] VBAT power-on flag will be reset when entering normal operating mode.
Wake-up requests are recognized by the transceiver through two possible channels:
• The bus lines for remote wake-up
• Pin WAKE for local wake-up
In order to wake-up the transceiver remotely through the bus lines, a filter mechanism is
integrated. This mechanism makes sure that noise and any present bus failure conditions
do not result into an erroneous wake-up. Because of this mechanism it is not sufficient to
simply pull the CANH or CANL bus lines to a dominant level for a certain time. To
guarantee a successful remote wake-up under all conditions, a message frame with a
dominant phase of at least the maximum specified tdom(CANH) or tdom(CANL) in it is required.
TJA1055_4
© NXP B.V. 2009. All rights reserved.
Product data sheet
Rev. 04 — 17 February 2009
7 of 26
NXP [ NXP ]
