UJA1161 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 2 — 17 April 2014 7 of 27
NXP Semiconductors
UJA1161
Self-supplied high-speed CAN transceiver with Standby mode
[1] V
BUF
is switched on in Standby mode if a CAN wake-up pattern is detected on the bus; if pin STBN does not go HIGH within t
to(silence)
,
V
BUF
is switched off again. V
BUF
is also switched on in Standby mode if STBN goes HIGH to select Normal mode.
6.1.2 Mode control via pin STBN
The UJA1161 can be switched between Normal and Standby modes via the STBN control
input (see Figure 3
). When STBN goes LOW, the UJA1161 switches to Standby mode.
When STBN goes HIGH, the UJA1161 switches to Normal mode.
6.2 Power supplies
6.2.1 Battery supply voltage (V
BAT
)
The internal circuitry is supplied from the battery via pin BAT. The device needs to be
protected against negative supply voltages, e.g. by using an external series diode. If V
BAT
falls below the power-off detection threshold, V
th(det)poff
, the UJA1161 switches to Off
mode, which means that the internal 5 V CAN supply and other internal logic (except for
power-on detection) are shut down.
The UJA1161 switches from Off mode to Standby mode t
startup
after the battery voltage
rises above the power-on detection threshold, V
th(det)pon
. A power-on event is indicated by
a LOW level on pin RXD. RXD remains LOW from the moment UJA1161 exits Off mode
until it switches to Normal mode.
6.2.2 CAN supply voltage (V
BUF
)
V
BUF
provides the internal CAN transceiver with a 5 V supply. The output voltage on BUF
is monitored. If V
BUF
falls below the 90 % undervoltage threshold (90 % of the nominal
V
BUF
output voltage), the CAN transceiver switches to (or remains in) Offline mode.
6.3 High-speed CAN transceiver
The integrated high-speed CAN transceiver is designed for active communication at bit
rates up to 1 Mbit/s, providing differential transmit and receive capability to a CAN protocol
controller. The transceiver is ISO 11898-2 and ISO 11898-5 compliant. The CAN
transmitter is supplied from V
BUF
. The UJA1161 includes additional timing parameters on
loop delay symmetry to ensure reliable communication in fast phase at data rates up to
2 Mbit/s, as used in CAN FD networks.
The CAN transceiver supports autonomous CAN biasing as defined in ISO 11898-6,
which helps to minimize RF emissions. CANH and CANL are always biased to 2.5 V when
the UJA1161 is in Normal mode with V
BUF
> 90 % threshold.
Autonomous biasing is active when the UJA1161 is in Standby mode with the CAN
transceiver in CAN Offline mode - to 2.5 V if there is activity on the bus (CAN Offline Bias
mode) and to GND if there is no activity on the bus for t > t
to(silence)
(CAN Offline mode).
This is useful when the node is disabled due to a malfunction in the microcontroller. The
transceiver ensures that the CAN bus is correctly biased to avoid disturbing ongoing
communication between other nodes. The autonomous CAN bias voltage is derived
directly from V
BAT
.
