ISL5586 Datasheet, PDF (12/20 Pages) Intersil Corporation – Low Power Ringing SLIC for Home Gateways

ISL5586
The terms t_R and t_S represent the cadence. The ringing
interval is t_R and the silent interval is t_S . A typical cadence
ratio t_R:t_S is 1:2.
The quiescent power of the device in the Ringing mode is
defined in Equation 32.
P_r(Q) = V_BH × I_BHQ + V_BL × I_BLQ + V_CC × I_CCQ
(EQ. 32)
The total power during the ringing interval is the sum of the
quiescent power and loading power:
P_r = P_r(Q) + V_BH × I_AVG – -_Z----_R----_E----_N-^V----^R2_+----^M-_R----^SL----_O----_O-----_P-
(EQ. 33)
For sinusoidal waveforms, the average current, I_AVG, is
defined in Equation 34.
I_AVG=


2_{π--}
Z^-----_R^--V--_E^--R--_N^{--M---+--S---}R^--×--_L^----_O^---2-_O^-----_P^-
(EQ. 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 600Ω load across the outputs of the Tip
and Ring amplifiers as shown below.
TIP
RING
600Ω
TIP AMP
RING AMP
FIGURE 9. FORWARD LOOP BACK INTERNAL TERMINATION
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
30kΩ. 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.
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.
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