OUT+

OUT-

SCAN90004

Receiver

IN+

IN-

100: Differential T-Line

100:

LVDS

Driver

SCAN90004

www.ti.com

SNLS182P – MAY 2005 – REVISED APRIL 2013

Design-for-Test (DfT) Features

IEEE 1149.1 (JTAG) SUPPORT

The SCAN90004 supports a fully compliant IEEE 1149.1 interface. The Test Access Port (TAP) provides access

to boundary scan cells at each LVTTL I/O on the device for interconnect testing. Differential pins are included in

the same boundary scan chain but instead contain IEEE1149.6 cells. IEEE1149.6 is the improved IEEE standard

for testing high-speed differential signals.

Refer to the BSDL file located on TI’s website for the details of the SCAN90004 IEEE 1149.1 implementation.

IEEE 1149.6 SUPPORT

AC-coupled differential interconnections on very high speed (1+ Gbps) data paths are not testable using

traditional IEEE 1149.1 techniques. The IEEE 1149.1 structures and methods are intended to test static (DC-

coupled), single ended networks. IEEE 1149.6 is targeted for the testing of high-speed differential (including AC

coupled) networks. The SCAN90004 includes circuitry to support AC-coupled testing on all differential inputs and

outputs and offers limited test capability. The limitations are due to several application specific factors (board

layout, capacitor value, data rate etc.), and also IO compliance (LVDS links in general are DC coupled). The

SCAN90004 has not been tested for full compliance or full compatibility to the IEEE1149.6 standard. Testing of

the device in the targeted application with the appropriate JTAG software will determine what extent of IEEE

1149.6 support is provided by the device.

FAULT INSERTION

Fault Insertion is a technique used to assist in the verification and debug of diagnostic software. During system

testing faults are "injected" to simulate hardware failure and thus help verify the monitoring software can detect

and diagnose these faults. In the SCAN90004 an IEEE1149.1 "stuck-at" instruction can create a stuck-at

condition, either high or low, on any pin or combination of pins. A more detailed description of the stuck-at

feature can be found in TI Applications note AN-1313 (SNLA060).

Application Information

INPUT INTERFACING

The SCAN90004 accepts differential signals and allow simple AC or DC coupling. With a wide common mode

range, the SCAN90004 can be DC-coupled with all common differential drivers (i.e. LVPECL, LVDS, CML). The

following three figures illustrate typical DC-coupled interface to common differential drivers. Note that the

SCAN90004 inputs are internally terminated with a 100

Ω resistor.

Figure 3. Typical LVDS Driver DC-Coupled Interface to SCAN90004 Input

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Product Folder Links: SCAN90004