ISL5586FCMZ datasheet(12/20 Pages) RENESAS

12 / 20 page

ISL5586

FN4924 Rev 2.00

Page 12 of 20

Nov 3, 2004

The terms tR and tS represent the cadence. The ringing

interval is tR and the silent interval is tS . A typical cadence

ratio tR:tS is 1:2.

The quiescent power of the device in the Ringing mode is

defined in Equation 32.

The total power during the ringing interval is the sum of the

quiescent power and loading power:

For sinusoidal waveforms, the average current, IAVG, is

defined in Equation 34.

The silent interval power dissipation will be determined by

the quiescent power of the selected operating mode.

Forward Loop Back Mode

Overview

The Forward Loop Back mode (FLB, 101) provides test

capability for the SLIC. An internal signal path is enabled

allowing for both DC and AC verification by the connection of

an internal 600 ohm resistor across Tip and Ring. This

internal terminating resistor has a tolerance of

10% at room

temperature. The device is intended to operate from only the

low battery during this mode.

Architecture

When the forward loop back mode is initiated internal

switches connect a 600

 load across the outputs of the Tip

and Ring amplifiers as shown below.

DC Verification

When the internal signal path is provided, DC current will

flow from Tip to Ring. The DC current will force DET low,

indicating the presence of loop current. In addition to

verifying device functionality, toggling the logic output

verifies the interface to the system controller.

AC Verification

The entire AC loop of the device is active during the forward

loop back mode. Therefore a 4-wire to 4-wire level test

capability is provided. Depending on the transhybrid balance

implementation, test coverage is provided by a one or two

step process.

System architectures which cannot disable the transhybrid

function would require a two step process. The first step

would be to send a test tone to the device while on hook and

not in forward loop back mode. The return signal amplitude

would be the test signal amplitude times the gain of the

transhybrid amplifier. Since the device would not be

terminated in the on hook mode, cancellation would not

occur. The second step would be to program the device to

FLB mode and resend the test tone. The return signal would

be much lower in amplitude than the first step, indicating the

device was active and the internal termination attenuated the

return signal.

System architectures which can disable the transhybrid

function would achieve test coverage with a signal step.

Once the transhybrid function is disabled the SLIC can be

programmed to the FLB mode and the test tone can be sent.

The return signal level is determined by the 4-wire to 4-wire

gain of the SLIC times the amplitude of the signal sent.

Tip Open/Ground Start Mode

Overview

The Tip Open mode (TO, 110) is intended for compatibility

with PBX type interfaces. The device does not provide

transmission capability in this mode which is intended for idle

line conditions. Loop supervision is provided by the switch

hook detector and either high or low battery operation is

supported.

Functionality

During Tip Open operation, the Tip switch is disabled and

the Ring switch is enabled. The minimum Tip impedance is

30k

. The only active path through the device will be

through the Ring switch.

In keeping with the MTU characteristics of the device, Ring

will not exceed -56V when operating from the high battery.

Though MTU does not apply to Tip Open, safety

requirements are satisfied.

PrQ



VBH IBHQ



VBL IBLQ



VCC ICCQ



(EQ. 32)

PrQ



VBH IAVG



VRMS

ZREN RLOOP

------------------------------------------

–

(EQ. 33)

IAVG



---



 VRMS



ZREN RLOOP

------------------------------------------

(EQ. 34)

FIGURE 9. FORWARD LOOP BACK INTERNAL TERMINATION

RING AMP

TIP AMP

RING

TIP

600



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