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j_oehmen
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Moderator 10 replies posted 5 replies posted 10 questions asked
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How to implement unidirectional error bus diagnosis for a combine tail/stop light?
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j_oehmen
Moderator
Moderator 10 replies posted 5 replies posted 10 questions asked
Moderator
Exceptional error handlings when having multiple devices, e.g. for TAIL/STOP applications, can be implemented with LITIX™ Basic+. This is useful if the light function, where the error occurs, determines which LED driver to turn off and which LED driver to keep on. For example if the LEDs of the TAIL light have an error, only the TAIL light may be turned off and the STOP light may be kept on. On the other hand, if the LEDs of the STOP light fails, all STOP and TAIL shall be turned off.
There are two solutions:

Solution 1:
Connect the ERRN node of the Tail/Stop part to the enable circuit of the Tail part:
4775.attach

Due to the voltage thresholds of the EN/DEN pin (the lowest is 1.4V) there is some margin.
Advantage here is that the devices disabled via EN/DEN consume almost no current (<2µA)
This can be used in case no additional turn off delay via a capacitor at the D-pin is required.

Solution 2:
The ERRN network needs to be split by a diode and place RERRN pull up resistors on either side of the diode:
4774.attach


The resistors and diode have to be designed such that the voltage VERRN goes below 0.8V in an error case. Therefore one also needs to consider the forward voltage of the diode because a small current (e.g. 0.5-1mA) is flowing through it. The remaining ERRN voltage of the device pulling down the node is also depending on the current which is flowing into it. A Schottky diode is beneficial due to the low voltage drop.

See also the application note on diagnosis and fault management and have a look at the LITIX Basic+ page

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j_oehmen
Moderator
Moderator 10 replies posted 5 replies posted 10 questions asked
Moderator
Exceptional error handlings when having multiple devices, e.g. for TAIL/STOP applications, can be implemented with LITIX™ Basic+. This is useful if the light function, where the error occurs, determines which LED driver to turn off and which LED driver to keep on. For example if the LEDs of the TAIL light have an error, only the TAIL light may be turned off and the STOP light may be kept on. On the other hand, if the LEDs of the STOP light fails, all STOP and TAIL shall be turned off.
There are two solutions:

Solution 1:
Connect the ERRN node of the Tail/Stop part to the enable circuit of the Tail part:
4775.attach

Due to the voltage thresholds of the EN/DEN pin (the lowest is 1.4V) there is some margin.
Advantage here is that the devices disabled via EN/DEN consume almost no current (<2µA)
This can be used in case no additional turn off delay via a capacitor at the D-pin is required.

Solution 2:
The ERRN network needs to be split by a diode and place RERRN pull up resistors on either side of the diode:
4774.attach


The resistors and diode have to be designed such that the voltage VERRN goes below 0.8V in an error case. Therefore one also needs to consider the forward voltage of the diode because a small current (e.g. 0.5-1mA) is flowing through it. The remaining ERRN voltage of the device pulling down the node is also depending on the current which is flowing into it. A Schottky diode is beneficial due to the low voltage drop.

See also the application note on diagnosis and fault management and have a look at the LITIX Basic+ page
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