Digital SLIC for 5V ISDN line cards
The TP3420AV308 is a digital subscriber line interface circuit (SLIC) from the TP3420 family, designed as a basic-function, single-channel interface for ISDN telecom equipment. It operates from a 4.75V to 5.25V supply rail, the standard for legacy 5V digital loop carrier and PBX line card designs.
Supply rail and interface fit
The 4.75V to 5.25V supply range means this SLIC expects a regulated 5V rail with ±5% tolerance. If your BOM uses a 3.3V-only backplane, this part will not drop in without a local 5V regulator. The ISDN interface is the defining feature — this is not a generic analog SLIC for POTS; it is specific to ISDN basic-rate access, typically used in NT1, TA, or central-office line termination cards.
Package and assembly note
The 20-PLCC with J-leads (20-LCC J-Lead) is a known footprint for telecom SLICs. J-leads allow visual inspection of solder joints, which is useful for field-repair scenarios. The 9x9 mm body is compact for a 20-pin device. No exposed thermal pad — dissipation is through the leads and PCB copper. RoHS non-compliant per the listing, so verify your assembly's solder alloy and exemption requirements if you are running a lead-free line.
Lifecycle and sourcing posture
For a telecom SLIC that may be supporting long-lifefield ISDN infrastructure, this means you can qualify it for new production runs without immediate obsolescence risk.