LCR1210-R100F datasheet(36/59 Pages) SKYWORKS

36 / 59 page

Si32260/1

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

Rev. 1.4 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • October 7, 2021

5.17. In-Circuit and Metallic Loop Testing

(MLT)

A rich set of features is provided for in-circuit testing of

the FXS system and the connected telephone line

(MLT):



Tone generators



Audio diagnostic filters



Digital and analog loop-back modes



Internal test load



Monitor ADC



DSP algorithms

Using these facilities, it is possible to test the

Si32260/1’s dc-dc converter, codec, line-feed, PCM bus

interface, DSP, SPI bus interface, and call progress

state-machine as well as testing the connected

telephone line and external protection circuitry.

The audio diagnostic filters on the FXS are intended to

provide programmable filtering of the TX digital audio

signal and calculate the peak and/or average signal

power of the filters’ outputs. The signal powers are then

compared

programmable

thresholds.

The

programmable filters can be used to band-pass filter a

certain tone or notch out certain tones, so that the signal

power measurements are frequency selective. This

filtering is useful in a telephony system because it can

measure harmonic distortion, intermodulation, noise,

etc.

The Si32260/1 incorporates an internal test load with a

2.2 k

 nominal value that can be connected across

Tip/Ring (Figure 24). The audio diagnostics system and

built-in test load can be used to test the FXS interface

(Si32260/1) itself without requiring an external load, a

connected line, or any relays. This facility can be used

for production and in-service testing of such things as:



Dial tone draw/break



Audio quality measurements



Pulse digit detection



DC feed



Ringtrip



Polarity reversal



Transmission loss

MLT, e.g., GR-909, is facilitated by the built-in DSP,

monitor ADC, and test load. They provide the ability to

detect multiple fault conditions within the CPE as well as

on the Tip/Ring pair (T-R). Thirteen different measured

and/or calculated parameters are reported by the

Monitor ADC. Host software for use in conjunction with

the ProSLIC API is available from Skyworks Solutions.

Typical MLT tests include:



Hazardous Potential Test – This checks for ac

voltage > 50 VRMS or dc voltage > 135 V between

Tip and Ground (T-G) or Ring and Ground (R-G).



Foreign Electromotive Force Test – Checks T-G or

R-G for ac voltage > 10 VRMS or dc voltage > 6 V.

Uses same threshold as for hazardous voltage test.



Resistive Faults Test – Checks for dc resistance

from T-R, T-G or R-G. Any measurement < 150 k

 is

considered a resistive fault.



Receiver-Off-Hook Test – Distinguishes between a

T-R resistive fault and an off-hook condition.



Ringers Test – Measures the magnitude of the

connected ring load (REN) across T-R. Results are

> 0.175 REN and < 5 REN for a valid load



AC Line Impedance (line length) – T-R, T-G, and R-

G. Generates a tone at several specific frequencies

(audio band) and measures the reflected signal

amplitude (complex spectrum) that comes back (with

transhybrid balance filter disabled). The reflected

signal is then used to calculate the line impedance

based on certain assumptions of wire gauge, etc.



Line Capacitance – T-R, T-G, R-G. Generates a

linear ramp function with polarity reversal, and

measures the time constant.

Diagnostic information is available even in the presence

of fault conditions that cause the system’s protection

devices (fuses, PTCs, etc.) to open. A high-impedance

sensing path (pins SRINGC and STIPC) can be used to

measure the conditions on Tip/Ring even when the FXS

system is effectively disconnected from the line. No

relay is required and this sensing path inherently meets

Dielectric Withstand per GR-49 (> 1000 V).

Figure 24. Si32260/1 Internal Test Load Circuit

TIP

RING

Test Load

RTL = 2.2 k (typical)

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