I am working on Truck OBD communication systems.
I designed a prototype card and used ADG1406 for get communication with Truck's different communication pins. I added "multiple TVS"s for protect to MUX's pins.
I use battery voltage 24V for ADG1406's Vcc.
One of the truck pin has 24V voltage. It is not battery voltage pin. And also it is not communication pin. I don't know purpose of that pin.
When the vehicle's ignition is off, that pin stays 0V.
When the vehicle's ignition is on, that pin jumps 24V.
I tried two methods:
1-)While ignition is off, i plug the card to OBD socket "then i open the ignition" and i don't have any problem.
2-)While ignition is on, i plug the card to OBD socket and that pin burn the ADG1406's connected switch pin. After that ADG1406 doesn't work anymore and warming up fastly.
I designed new card and i added "resettable PTC fuse" to that pin.
While ignition is on, i plug the new card to OBD socket and that pin burn the ADG1406's connected switch pin and PTC fuse activated. After that ADG1406 works except that pin.
In datasheet, it says:
"ICs capable of 33 V operation"
So what is the problem?
The ADG1406 is only guaranteed with +/-16.5V dual supply operation max or single 16.5V supply.
See datasheet, end of Table 3, page 5.
(The part will probably be functional with 24V supply.)
We have a 16:1 mux, the ADG5206 which is fully specified and has guaranteed operation with 36V single supply. http://www.analog.com/static/imported-files/data_sheets/ADG5206_5207.pdf
This is pin-pin with the ADG1406 in TSSOP package.
For 2) above Is it possible when you connect in the OBD socket that the 24V is applied to the ADG1406 switch input before the part is powered? The ADG1406 has internal ESD protection diodes on its switch inputs to the supplies and these will be forward biased, drawing current, if inputs exceed Vdd by ~0.6V. If current is not limited (<<30ma) part will be damaged.
We have fault protected muxes 8:1 muxes, ADG438F that are designed to handle over-voltages on inputs without supplies present. http://www.analog.com/en/interface-isolation/protection-products/adg438f/products/product.html
1-) At Table7("Absolute Maximum Ratings")
VDD to VSS 35V.
I tested the chip with 24V single supply during 48 hours. It worked without problem.
The problem doesn't look like "wrong single supply operation".
I bought 1000 pieces of this chips. So i can't give up
Can i change this chips with other one?
For 2) above Is it possible when you connect in the OBD socket that the 24V is applied to the ADG1406 switch input before the part is powered?
I use LC filter for power strikes. I use it just for supply. Switch inputs don't have any lc filter, just TVS.
Does it causes problem that you mention about?
If yes, What do you offer for solution?
By the way i use a pin to pin chip from another manufacturer. It worked without problem.
As I stated the ADG1406 maybe functional with 24V supply but we do not guarantee the performance or lifetime of the part at this supply. I recommend the ADG5206 as alternative.
If you will have a 24V input on your switch input without power, then I would recommend that you use series R to limit current to <30mA range and place Schottky diodes to the supplies. See link to article for more details. http://www.analog.com/library/analogDialogue/archives/45-05/switch_mux.html
What is the breakdown and clamp voltage of the TVS used?
I recommend the ADG5206 as alternative.
If you will have a 24V input on your switch input without power, then I would recommend that you use series R to limit current to <30mA range and place Schottky diodes to the supplies.
I already placed Schottky diode to the supply. I placed 100-1000 ohm resistor like you said and it fixed the problem. Normally I have to place 1K for limiting current to <30mA range. But it causes another problem at another vehicle. So i placed 100 ohm resistor. I am still testing.
Thanks for help.