We are using ADP5585 in our design for interfacing to a keyboard. The schematics is as shown in the attachment. The lines KBC0,1,2,3 and KBR0,1,2,3 are going to a 4 X 4 matrix KEYPAD connected with about 15 inches long ribbon cable.
The capacitors C2,C4,C6,C8, C67,C68,C69,C74 though are shown in schematics are not really mounted on board.
The device TPD8F0003DQDR is being used as ESD protection device Its link is http://www.ti.com/lit/ds/symlink/tpd6f003.pdf
we are noticing that in spite of using above ESD protection device we are seeing failures of the ADP5585 device. The failed devices basically have less than 50 ohm resistance between any of the I/O pins and GND. Incidentally we are seeing that even the lines which are not connected to KEYPAD like pin numbers 16, 10 and 1 which are connected to internal signals also develop this low resistance between that specific pin and GND.
Also these failures Occur only after a few days of usage typically 5-10 days with KEYPAD being used about 10-15 times per days
1. Has anyone else or even Analog devices have seen these kind of failures happening with ADP5585
2. Is there any other issues in the schematics attached ?
3. Is there really a ESD issue or is it for any other reason that the ADP5585 device may be going bad ?
4. Should we use any other ESD protection device than the currently used ? probably the clamping voltage of the device we are using is little bit higher than the transient tolerance limit of ADP5585