[XC2000/XE166] Interfacing dual powered uC with CAN bus transceiver TLE6251DS !?

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Hi!

Usually one would use the TLE6250GV33 CAN-Bus transceiver when using a XC2000/XE166
with dual power supply (3.3V for Digital, 5V for Analog).

Now if we want to use terminal 15/30 applications (German: Teilnetzbetrieb), one can not go
for the TLE6250.

When looking at the datasheet of the TLE6251DS, which is "...designed to provide an
excellent passive behavior when the transceiver is switched off (mixed networks, terminal
15/30 applications)
", I'm woundering how this can work together with the aforementioned
micro-controller.

The datasheet specifies in table 5 only a HIGH/LOW level output current on the RxD pin.
The TxD pin is being specified with a min. HIGH level voltage of 2.0V, so this input is
definitely compatible to 3.3V logic.

Looking at the datasheet of the eg. XC2336B in table 12, an "Absolute sum of overload
currents" is being specified.

Can I therefore assume, if taking all other possible overload currents into account,
one can directly attach the TLE6251DS to a dual powered XC2000/XE166 micro-
controller? Or can it directly interface to 3.3V logic?

MfG/Regards
Friedl
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3 Replies
Markus_Kroh
Employee
Employee
Hi Freidl,

Sorry, your post somehow was not visible for a while.

I forward your question to our Power experts and hope to get the answer asap.

Greetings

Markus
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Markus_Kroh
Employee
Employee
TLE6251DS
- The TxD input pin has TTL input levels, so no issue if MCU output is max 3.3V or 5V. Above 2.0V the signal is anyway regarded HIGH.
- The RxD output has a Push-Pull stage. E.g. when HIGH it will output 5V. If this is interfaced directly to a digital 3.3V input on the MCU it will be out of spec and may be damaged. Therefore the customer needs a transceiver with VIO pin (e.g. TLE7250GVIO or TLE6251D) or a level shifting/current limiting circuit. The simplest is a series resistor for limiting the current, e.g. voltage drop of 5V – 3.3V = 1.7V and be within the overload level of the MCU. With a two resistor voltage divider completely safe voltage levels for the MCU can be obtained. For both of these last options there is a drawback that the RC combination of the resistor(s) and MCU input pin capacitance will filter / delay the signal. The filter may be good for EMC, but the propagation delay has to be inspected / verified. I know of car makers that does not allow the series resistor solution because of this…
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Not applicable
Markus Kroh wrote:

TLE6251DS
- The TxD input pin has TTL input levels, so no issue if MCU output is max 3.3V or
5V. Above 2.0V the signal is anyway regarded HIGH.
- The RxD output has a Push-Pull stage.


After looking at the datasheet again and again at least 10 times, I now understand
why I did interpret the datasheet wrongly.



So it is not possible to directly interface the TLE6251DS with a 3.3V powered
microcontroller as you say:

Markus Kroh wrote:

E.g. when HIGH it will output 5V. If this is interfaced directly to a digital 3.3V
input on the MCU it will be out of spec and may be damaged. Therefore the
customer needs a transceiver with VIO pin (e.g. TLE7250GVIO or TLE6251D) ....


You probably mean the TLE8250GVIO as there is no TLE7250GVIO.

Infineon datasheets seem to be the other way round when it comes to ordering
of the columns compared to the rest of the world. The "Remarks" column should
rather be put between "Parameter" and "Symbol" column and renamed "Conditions"
like in this example:



Thanks for your help. Have to try to fix the already produced boards now 😞

Regards
Friedl
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