Product data

UJA1167 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 2 — 18 April 2014 19 of 60
NXP Semiconductors
UJA1167
Mini high-speed CAN system basis chip with Standby/Sleep modes &
watchdog
The default value of VEXTC at power-on is defined by bits VEXTSUC in non-volatile
memory (see Section 6.11
).
In contrast to pin INH, pin VEXT is disabled when the SBC switches to Overtemp mode.
The status of VEXT can be read from the Supply voltage status register (Table 13
).
6.7 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 V1. The UJA1167 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 transceiver is in Active or Listen-only modes (CMC = 01/10/11).
Autonomous biasing is active 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
SBC 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
.
6.7.1 CAN operating modes
The integrated CAN transceiver supports four operating modes: Active, Listen-only,
Offline and Offline Bias (see Figure 5
). The CAN transceiver operating mode depends on
the UJA1167 operating mode and on the setting of bits CMC in the CAN control register
(Table 14
).
When the UJA1167 is in Normal mode, the CAN transceiver operating mode (Active,
Listen-only or Offline) can be selected via bits CMC in the CAN control register (Table 14
).
When the UJA1167 is in Standby or Sleep modes, the transceiver is forced to Offline or
Offline Bias mode (depending on bus activity).
6.7.1.1 CAN Active mode
In CAN Active mode, the transceiver can transmit and receive data via CANH and CANL.
The differential receiver converts the analog data on the bus lines into digital data, which
is output on pin RXD. The transmitter converts digital data generated by the CAN
controller (input on pin TXD) into analog signals suitable for transmission over the CANH
and CANL bus lines.
CAN Active mode is selected when CMC = 01 or 10. When CMC = 01, V1/CAN
undervoltage detection is enabled and the transceiver will go to CAN Offline or CAN
Offline Bias mode when the voltage on V1 drops below the 90 % threshold. When
CMC = 10, V1/CAN undervoltage detection is disabled. The transmitter will remain active
until the voltage on V1 drops below the V1 reset threshold (selected via bits V1RTC). The
SBC will then switch to Reset mode and the transceiver will switch to CAN Offline or CAN
Offline Bias mode.