UJA1078 Datasheet, PDF (20/53 Pages) NXP Semiconductors – High-speed CAN/dual LIN core system basis chip

NXP Semiconductors
UJA1078
High-speed CAN/dual LIN core system basis chip
6.6 Power supplies
6.6.1 Battery pin (BAT)
The SBC contains a single supply pin, BAT. An external diode is needed in series to
protect the device against negative voltages. The operating range is from 4.5 V to 28 V.
The SBC can handle maximum voltages up to 40 V.
If the voltage on pin BAT falls below the power-off detection threshold (V_th(det)poff), the
SBC immediately enters Off mode, which means that the voltage regulators and the
internal logic are shut down. The SBC leaves Off mode for Standby mode as soon as the
voltage rises above the power-on detection threshold, V_th(det)on. The POSI bit in the
Int_Status register is set to 1 when the SBC leaves Off mode.
6.6.2 Voltage regulator V1
Voltage regulator V1 is intended to supply the microcontroller, its periphery and additional
transceivers. V1 is supplied by pin BAT and delivers up to 250 mA at 3.3 V or 5 V
(depending on the UJA1078 version).
To prevent the device overheating at high ambient temperatures or high average currents,
an external PNP transistor can be connected as illustrated in Figure 6. In this
configuration, the power dissipation is distributed between the SBC and the PNP
transistor. Bit PDC in the Mode_Control register (Table 5) is used to regulate how the
power dissipation is distributed − if PDC = 0, the PNP transistor will be activated when the
load current reaches 85 mA (50 mA if PDC = 1) at T_vj = 150 °C. V1 will continue to deliver
85 mA while the transistor delivers the additional load current (see Figure 7 and Figure 8).
battery
VEXCTRL
VEXCC
UJA107x
BAT
V1
Fig 6. External PNP transistor control circuit
015aaa098
UJA1078_2
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 02 — 27 May 2010
© NXP B.V. 2010. All rights reserved.
20 of 53