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 17 of 60
NXP Semiconductors
UJA1167
Mini high-speed CAN system basis chip with Standby/Sleep modes &
watchdog
6.4 Global temperature protection
The temperature of the UJA1167 is monitored continuously, except in Sleep and Off
modes. The SBC switches to Overtemp mode if the temperature exceeds the
overtemperature protection activation threshold, T
th(act)otp
. In addition, pin RSTN is driven
LOW and V1, VEXT and the CAN transceiver are switched off. When the temperature
drops below the overtemperature protection release threshold, T
th(rel)otp
, the SBC
switches to Standby mode via Reset mode.
In addition, the UJA1167 provides an overtemperature warning. When the IC temperature
rises about the overtemperature warning threshold (T
th(warn)otp
), status bit OTWS is set
and an overtemperature warning event is captured (OTW = 1).
6.5 Power supplies
6.5.1 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 SBC switches to Off mode.
However, the microcontroller supply voltage (V1) remains active until V
BAT
falls below 2 V.
The SBC switches from Off mode to Reset mode t
startup
after the battery voltage rises
above the power-on detection threshold, V
th(det)pon
. Power-on event status bit PO is set to
1 to indicate the UJA1167 has powered up and left Off mode (see Table 20
).
6.5.2 Low-drop voltage supply for 5 V microcontroller (V1)
V1 is intended to supply the microcontroller and the internal CAN transceiver and delivers
up to 150 mA at 5 V. The output voltage on V1 is monitored. A system reset is generated
if the voltage on V1 drops below the selected undervoltage threshold (60 %, 70 %, 80 %
or 90 % of the nominal V1 output voltage, selected via V1RTC in the V1 and INH/VEXT
control register; see Table 12
).
The internal CAN transceiver consumes 50 mA (max) when the bus is continuously
dominant, leaving 100 mA available for the external load on pin V1. In practice, the typical
current consumption of the CAN transceiver is lower (25 mA), depending on the
application, leaving more current available for the load.
The default value of the undervoltage threshold at power-up is determined by the value of
bits V1RTSUC in the SBC configuration control register (Table 8
). The SBC configuration
control register is in non-volatile memory, allowing the user to define the undervoltage
threshold (V1RTC) at start-up.
In addition, an undervoltage warning (a V1U event; see Section 6.10
) is generated if the
voltage on V1 falls below 90 % of the nominal value (and V1U event detection is enabled,
V1UE = 1; see Table 25
). This information can be used as a warning, when the 60 %,
70 % or 80 % threshold is selected, to indicate that the level on V1 is outside the nominal
supply range. The status of V1, whether it is above or below the 90 % undervoltage
threshold, can be read via bit V1S in the Supply voltage status register (Table 13
).