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AG1170

+5V / +3.3V Low Power Ringing SLIC

Unspecified 

V1.9 September 2006

Data Sheet

2.0 Line Interfacing

As well as being used in an electrically demanding

environment, the needs of different applications and

regulatory standards means that the SLIC must be

flexible, and have facilities to ensure robust

performance. The Ag1170 SLIC provides a complete

and flexible interface to the telephone line.

2.1 Battery Feed

The Ag1170 has an integral DC/DC converter, which

generates the battery voltage in the device. This

means that only a supply of +5V or 3.3V is needed,

unlike conventional SLICs which will also need a

battery voltage of anything between -20V and -60V

(-75V for ringing). This confers a significant cost, space

and time to market benefit on the equipment designer.

The battery feed to the telephone line is generated

from the positive supply rail. This provides a -48V

battery feed to the line driver, which is adjusted

automatically to match line conditions.

Ag1170

+5V / +3.3V LOW POWER RINGING SLIC

also guaranteed not give a false ring trip with a load of

3 REN.

2.3 Power Down and Synchronisation

The DC/DC converter can be switched off by applying

a logic 0 to the PD input. The SLIC takes 50ms to

power up from this powered down state. Logic outputs

are not valid during this time. When using the power

down function, it is recommended that the SLIC is

polled (powered up periodically) to check for SHK (the

subscriber has gone off-hook). If not in Power Down

mode, the PD pin should be left open circuit. An open-

collector gate should be used for applying the PD

signal. Never connect a logic high to the PD pin.

NOTE: This is a sensitive node; keep connections very

short.

The DC/DC has an internal oscillator. If desired, the

oscillator frequency may be synchronised with an

external clock for EMI reasons. To do this, a 128kHz

(+5V) or 64kHz (+3.3V) square wave (with 50:50 mark

space) should be inputted to the PD pin. See

Applications Note: AN1170-12, for further details.

Power efficiency is good, because the line is supplied

with only as much power as is needed. Little excess

heat is generated, even on short lines. The loop current

is pre-set to a constant 24mA, under the conditions

shown in Section 9.3 of this datasheet, which specifies

the ‘DC Electrical Characteristics’ for the Ag1170.

2.2 Ringing

The ringing signal is generated by switching the SLIC

into ringing mode, by setting the RM pin high, and then

toggling the F/R pin at the required frequency and

cadence. The toggling of the F/R pin produces a

balanced signal at Tip and Ring. These signal

waveforms are shown in Figure 4. Ringing voltage of

approximately 65Vrms is applied to a single handset. It

is important that the RM pin is only set high during

ringing and that this pin is set low at all other times.

Applications Note AN1170-14 provides advice on how

to implement this requirement.

3.0 The 2-4 Wire (hybrid) Conversion.

The Ag1170 SLIC transmits and receives balanced

2-wire analog signals at the Tip and Ring connections.

These are converted to a ground referenced output at

VOUT and from a ground referenced input at VIN.

The VOUT and VIN pins are normally connected to a

Codec for conversion of audio to and from a digital

Pulse Code Modulated (PCM) stream.

3.1 Transmit and Receive Gain.

The gain in both the transmit direction (Tip/Ring to

VOUT) and the receive direction (VIN to Tip/Ring) is set to

0dB. Normally any gain adjustments required by the

user can be made by programming the Codec.

3.2 The 2 Wire Impedance.

During ringing the integral DC/DC converter

automatically switches to produce a battery voltage of

-72V. This will produce greater than 40Vrms into a

REN of 3. The slope of the edges on the ringing

waveform is set internally to give the correct waveform

with 20Hz to 25Hz ringing frequency.

The 2 Wire impedance at Tip/Ring of the Ag1170 is set

to 600R. It requires no external programming resistors.

The 2 Wire impedance of the Ag1170-P can be

programmed to the required value by connecting

components across pins ZT1-ZT2.

When an “off-hook” condition occurs during ringing, the

ring-trip circuit on the Ag1170 senses the loop current

flowing and signals the off-hook condition on the SHK

output. The SHK signal must be “de-bounced” (by the

controlling processor) for 10ms to remove any spurious

pulses. The DC/DC controller limits the power. The

Ag1170 will operate continuously with a ring-trip load.

The ring-trip function will operate up to a loop

resistance of typically 800R (including telephone). It is

The impedance ratio for ZT is 100. Resistors should be

multiplied by the ratio and capacitor values divided by

the ratio to obtain the required programming values.

E.g. for 600R impedance, fit 60K resistor (nearest

value = 62K).

Further details on the programming of the Ag1170P are

contained within Applications Note: AN1170-1.

© Silver Telecom 2006

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