Reader PocketBook InkPad 3 – identification of a black component marked 'CT' on the microUSB line

[Maniackk]

Hello,

Device: PocketBook InkPad 3
Mainboard: XRZ_E091_PB740-VTTOA-V1.1 / 2017-10-12

I'm replacing the broken microUSB connector on this e-reader, and during inspection after desoldering, I noticed a loose black SMD component marked "CT". One of them was torn off along with the pad, while the other one (marked in the photo) is still in place.

I would appreciate help identifying this component.

Measuring the loose component with a multimeter gives 5.84 MΩ in both directions, while the one still on the board shows no measurable result.
The dimensions suggest it's in 0402 package.

From what I could trace visually, these components are located on the data lines of the microUSB port.

Thanks in advance for any help!

[mon2]

This will most likely be a UNIDIRECTIONAL, 0402 SMD TVS diode to protect the USB D+ / D- lines.

Configure your meter in DIODE mode. Red meter probe on the anode = back end of the DIODE arrow head; black meter probe to the bar side of the arrow head on the diode - meter should conduct. Reverse the meter leads and the meter should block = 'OL'. Confirm this test.

Repeat with the part on the board.

These parts are present to shunt and protect any excessive transients on the USB data lines. Many vendors offer replacement parts for this purpose including:




NOTE: The capacitance of the protection diode is very important. If the capacitance is too high, then the protected USB data line will be tardy on the rise / fall and will cause the USB port to fail at high data rates. Ideally, purchase a part that is rated for USB 3.0 / 3.1 data rates which will be ultra low in capacitance such as 0.3pf, etc. If the protection diode is with a high capacitance then that part was designed to protect the USB VBUS line which is a static voltage rail - not a pulsing one like the data lines on the USB connector.