L9613B Interface IC (Automotive app)

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Hi
Hi Everyone

Anyone ever used the above device? I'm concerned about the absolute maximum
rating for the K input, which, according to the data sheet, is not permitted
to exceed Vs. I assume that that Vs is intended to be the battery voltage,
and this can differ from point to point around the vehicle, and that the K
pin is meant to be pulled up to Vs at the chip.

Scenario:

- Two 9613's, in different places on the vehicle, have their K pins are
connected together by a wire,
- The wire is pulled up to Vs locally at each device by a 5k resistor,
- Both devices are off,
- Vs at one end is 13.5V, at the other end 12V

In the above,  the wire will try to sit at 12.75V (the lower Vs plus half
the difference, due to the divider action of the resistors), and therefore
the data sheet rating for the device at 12V will be exceeded.

Any opinions/experience?

Cheers

Geoff



Re: L9613B Interface IC (Automotive app)
Hi Geoffrey,

I presume your talking about a I-line bus.. it shouldn't make much of a
difference if both the Vs supplies are slightly different.

The K-line driver can only pull low on the bus... If there's is a current
between the 2 different Vs supplies, it will be very small, and limited by
the 2x5K resistors.

Quite often Vs will be different at different ECUs, usually depending on the
load that the ECU is supplying ( voltage drop on the supply cable ).

The LIN / K-line drivers usually have a fair degree of noise immunity on
their switching thresholds.

Hope this helps,
Dave.


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