UJA1069 datasheet(17/64 Pages) PHILIPS

17 / 64 page

UJA1069_2

Preliminary data sheet

Rev. 02 — 5 March 2007

17 of 64

NXP Semiconductors

UJA1069

LIN fail-safe system basis chip

The SBC also detects if pin RSTN is clamped HIGH. If the HIGH-level remains on the pin

for longer than tRSTN(CHT) while pin RSTN is driven internally to a LOW-level by the SBC,

the SBC falls back immediately to Fail-safe mode since the microcontroller cannot be

reset any more. By entering Fail-safe mode, the V1 voltage regulator shuts down and the

microcontroller stops.

Additionally, chattering reset signals are handled by the SBC in such a way that the

system safely falls back to Fail-safe mode with the lowest possible power consumption.

6.5.2 EN output

Pin EN can be used to control external hardware such as power components or as a

general purpose output if the system is running properly. During all reset events, when pin

RSTN is pulled LOW, the EN control bit will be cleared, pin EN will be pulled LOW and will

stay LOW after pin RSTN is released. In Normal mode and Flash mode of the SBC, the

microcontroller can set the EN control bit via the SPI. This results in releasing pin EN

which then returns to a HIGH-level.

6.6 Power supplies

6.6.1 BAT14, BAT42 and SYSINH

The SBC has two supply pins, pin BAT42 and pin BAT14. Pin BAT42 supplies most of the

SBC where pin BAT14 only supplies the linear voltage regulators and the INH/LIMP output

pin. This supply architecture allows different supply strategies including the use of

external DC-to-DC converters controlled by the pin SYSINH.

6.6.1.1

SYSINH output

The SYSINH output is a high-side switch from BAT42. It is activated whenever the SBC

requires supply voltage to pin BAT14, e.g. when V1 is on (see Figure 4 and Figure 8).

Otherwise pin SYSINH is ﬂoating. Pin SYSINH can be used to control e.g. an external

step-down voltage regulator to BAT14, to reduce power consumption in low-power modes.

6.6.2 SENSE input

The SBC has a dedicated SENSE pin for dynamic monitoring of the battery contact of an

electronic control unit. Connecting this pin in front of the polarity protection diode of the

ECU provides an early warning if the battery becomes disconnected.

6.6.3 Voltage regulator V1

The UJA1069 has an independent voltage regulator supplied out of the BAT14 pin.

Regulator V1 is intended to supply the microcontroller.

The V1 voltage is continuously monitored to provide the system reset signal when

undervoltage situations occur. Whenever the V1 voltage falls below one of the three

programmable thresholds, a hardware reset is forced.

A dedicated V1 supply comparator (V1 Monitor) observes V1 for undervoltage events

lower than VUV(VFI). This allows the application to receive a supply warning interrupt in

case one of the lower V1 undervoltage reset thresholds is selected.

The V1 regulator is overload protected. The maximum output current available from pin V1

depends on the voltage applied to pin BAT14 according to the characteristics section. For

thermal reasons, the total power dissipation should be taken into account.

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