ADG4613: Error causing voltage clipping

Hi,

I have a strange problem with one of our ADG4613: It clips the voltages at 1.4V.

We use the ADG4613 to separate our board from a bus system with multiple other boards connected to the same bus. The schematic is the following:

Schematic

The signals are transmitted correctly through the switch, so the voltage levels at the inputs and outputs are always the same, also waveforms are transmitted correctly.

However, the maximum voltage on the lines is limited to 1.4V. The outputs OUT_1/OUT_2 are connected to a high impedance load (which I confirmed to be working properly), the inputs have a 1kOhm pull-up to 3.3V.

To understand what exactly happens on this board, I disconnected the pull-up on the inputs and used a power supply to provide different voltage levels at IN_1 and measure the required current to keep this voltage level, the outcome is the following:

Current_Voltage_Plot

Above 1.8V the current draw stays at the measurement resolution of 0.2mA. I would actually expect the current draw to stay at this level for all applied currents.

In total, we have 6 boards with identical schematic, 5 of them work flawlessly so far, the problem appeared only on one board. However, this error is quite critical, as it prohibits any communication on the bus system between any of the other boards (not just ours). Therefore, we would really like to understand what has happened here and what is causing this error.

Could this be an error caused by ESD? In the ADG4613 data sheet, the section "Signals on Inputs with No Power Present" mentions "There are no internal ESD diodes from the analog or
digital inputs to VDD or VSS". Does this mean there is no ESD protection at all?

Many thanks in advance,

Jonas.