UJA1076 datasheet(18/47 Pages) NXP

18 / 47 page

UJA1076_2

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Product data sheet

Rev. 02 — 27 May 2010

18 of 47

NXP Semiconductors

UJA1076

High-speed CAN 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 (Vth(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, Vth(det)pon. 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 UJA1076 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 Tvj =150 °C. V1 will continue to deliver

85 mA while the transistor delivers the additional load current (see Figure 7 and Figure 8).

Fig 6.

External PNP transistor control circuit

UJA107x

VEXCTRL

VEXCC

015aaa098

BAT

battery

UJA1076 Datasheet(PDF) 18 Page - NXP Semiconductors