UJA1076 datasheet(22/47 Pages) NXP

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UJA1076_2

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Product data sheet

Rev. 02 — 27 May 2010

22 of 47

NXP Semiconductors

UJA1076

High-speed CAN core system basis chip

6.7.2 Split circuit

Pin SPLIT provides a DC stabilized voltage of 0.5VV2. It is activated in CAN Active mode

only. Pin SPLIT is floating in CAN Lowpower and Off modes. The VSPLIT circuit can be

used to stabilize the recessive common-mode voltage by connecting pin SPLIT to the

center tap of the split termination (see Figure 10).

A transceiver in the network that is not supplied and that generates a significant leakage

current from the bus lines to ground, can result in a recessive bus voltage of < 0.5VV2. In

this event, the split circuit will stabilize the recessive voltage at 0.5VV2. So a start of

transmission will not generate a step in the common-mode signal which would lead to

poor ElectroMagnetic Emission (EME) performance.

6.7.3 Fail-safe features

6.7.3.1

TXDC dominant time-out function

A TXDC dominant time-out timer is started when pin TXDC is forced LOW. If the LOW

state on pin TXDC persists for longer than the TXDC dominant time-out time (tto(dom)TXDC),

the transmitter will be disabled, releasing the bus lines to recessive state. This function

prevents a hardware and/or software application failure from driving the bus lines to a

permanent dominant state (blocking all network communications). The TXDC dominant

time-out timer is reset when pin TXDC goes HIGH. The TXDC dominant time-out time

also defines the minimum possible bit rate of 10 kbit/s.

6.7.3.2

Pull-up on TXDC pin

Pin TXDC has an internal pull-up towards VV1 to ensure a safe defined state in case the

pin is left floating.

6.8 Local wake-up input

The SBC provides 2 local wake-up pins (WAKE1 and WAKE2). The edge sensitivity

(falling, rising or both) of the wake-up pins can be configured independently via the WIC1

and WIC2 bits in the Int_Control register Table 6). These bits can also be used to disable

wake-up via the wake-up pins. When wake-up is enabled, a valid wake-up event on either

of these pins will cause a wake-up interrupt to be generated in Standby mode or Normal

Fig 10. Stabilization circuitry and application using the SPLIT pin

UJA1076

CANL

SPLIT

CANH

GND

VSPLIT = 0.5 VCC

in normal mode;

otherwise floating

015aaa121

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