Am79R1001JC - Legerity, Inc.

Pub. # 080458 Rev: C Amendment: /0

Issue Date: June 2001

Am79R100/101 Vs Am79R79

Device Comparison Brief

This article is a component of the Legerity RSLIC device documentation family; it discusses the

unique features of the Am79R100/101 devices, the similarities between the Am79R100/101

device features and the Am79R79 device features, as well as the differences between each

device.

TABLE OF CONTENTS

Table of Contents.............................................................................................................................1

What’s new?.....................................................................................................................................2

Sinusoidal Ringing Waveform..................................................................................................2

1. Sinusoidal Ringing Without DC offset ..........................................................................3

2. Sinusoidal Ringing with DC Offset on the Vring Pin or the Rref Pin............................3

3. Sinusoidal Ringing with DC Offset Between the Rref Pin and the Vring Pin ...............3

4. Legerity SLAC™ Device Interface................................................................................4

DC Feed...................................................................................................................................6

Anti-Satur at ion Reg ion.............................................................................................................6

Ring Trip...................................................................................................................................8

UL.............................................................................................................................................8

Protection Cir cuit......................................................................................................................8

Pinout Differ en ce......................................................................................................................8

Power Dissip ation .............................................................................................................. ......9

2 Am79R100/101 Vs Am79R79 Device Comparison Brief

WHAT’S NEW?

Some appl icat ions in Europe req uire s inu so idal ringing. A ll t he co mpa ni es in Kor e a req uir e

sinusoidal ringing of 70-90 volts, regardless of the application. We have found that some phones

will not ring with the Am79R79 device because they require a higher ringing voltage or DC offset

ringing, which are not required in TR57/TR909. In order to address broader markets and meet

these chall eng in g appl ic ati on s, Leger ity has intr o du ced the Am 79R 100 device and the

Am79R101 device. Each has balanced trapezoidal and sine wave ringing, and provides DC offset

operation at up to a 100 V battery. These new products raise the Legerity Ringing SLIC device

family to a new level.

The Am79R79 device, which provides balanced trapezoidal ringing, is sufficient for 5 REN in a

short loop (TR909) application. Its 70 Vpk provides 50 Vrms (with a crest factor of 1.25 to a load

of 1400 Ω with 2 x Rf = 100 Ω and Rline = 70 Ω, for a total = 1570 Ω). The Am79R100 device

has a higher ringing voltage. Its 90 Vpk provides 64 Vrms (with a cr est factor of 1.25 to a load

of 1400 Ω with 2 x Rf = 100 Ω and Rline = 70 Ω, for a total = 1570 Ω). Note that the Am79R101

device has less driving ability than the Am79R100 device due to its sine wave and 1.4 crest

factor. The unique features of the Am79R100/101 devices will ring those hard-to-ring phones or

push the loop length even further with the same ringer load.

Sinusoidal Ringing Waveform

The sinusoidal ringing waveform generated through the Am79R101 device has an

advantageously low distortion, and satisfies the traditional ringing waveform requirements of

small PBX, WLL, and Pairgain applications. It also has less crosstalk than trapezoidal ringing for

large PBX app li ca tio ns in multi- p air ca ble tran sm i ss ion . The Am79R101 devi ce al so offers offset

ringing, which is created by applying a DC bias voltage on the Rref or Vring pins, and satisfies

most phones that require an offset from ring to tip during the ringing. However, it should be noted

that trapezoidal ringing is usually more than adequate for most applications, and can provide a

good alternative for less power consumption compared to both the sinusoidal and offset ringing

options.

Figure 1 How to Generate DC Offset for Ringing (Vring and Rref Interface)

The Am79R100 device is no different than the Am79R79 device in its trapezoidal waveform

generation. Rslew and Cslew can be calculated by using the same formulas given previously

(refer to the Am79R79 device Ringing SLIC Device Technical Review).

For sinusoidal ringing with or without DC offset, there are a variety of ways to apply the ringing

signal to the device. These ways are explained in the following sections.

DC Offs et

Balanced Sinusoidal Ringing

with Offset

Rin

Waveform

VBat1

Am79R100/101 Vs Am79R79 Device Comparison Brief 3

1. Sinusoidal Ringing Without DC offset

Connect the Rref pin to the digital ground and feed the (desired frequency) sine wave signal to

Vring pin. No AC coupling capacitor is needed, but the amplitude has to be lower than 2 Vpk-pk

to avoid clipping. The sine wave is present at Vab, measured around (Vbat1)/2 V DC.

Figure 2 Balance Ringing Without DC Offse t

Am79R101 Device

VRING

RREF

Vring<2Vpk-p

2. Sinusoidal Ringing with DC Offset on the Vring Pin or the Rref Pin

Connect the Rref pin to the digital ground and use the voltage divider (shown in Figure 3) to

connect the Vring pin. The bias voltage range at the Vring pin should stay within a maximum of

Vcc/2. A DC blocking cap is needed to prevent upsetting the ring source. There is internal

impedance around 10K in series with the pin, so more voltage tolerance can be expected at Vab.

With a similar approach, the Rref pin can be biased with resistive dividers.

Figure 3 Ringing with DC Offset on Vring Pin

Am79R101 Device

Vring<2Vpk-pk

RR1

RR2

VRING

RREF

VCC

3. Sinusoidal Ringing with DC Offset Between the Rref Pin and the Vring Pin

Use two resistors to buil d a vo ltage d iv ider between t he V cc an d DG ND. Conne ct the ju ncti on

of the resistors to the Rr ef p in. The v oltage ran ge at the Rr ef pi n sho uld stay w ithin 0 V to

Vcc/2. App ly bias on Vr ing w ith hi gher ( or lower ) than the DC refer ence voltag e on Rr ef, and

observe the offset r inging waveform at Vab. If Vr ing < Vrr ef, the t ip i s negativ ely bia sed. If Vr in g

> Vrref, the tip is po siti vel y biase d. A bi gger offset may cr eate clipping on one side of th e

ringing waveform if the ampl itude is too high. T here i s a trade off between th e amp litude and

the DC offset. When both Rref and Vring are biased, the DC difference between inputs, times

100, is then equal to the offset voltage at Vab (shown in Figure 4).

4 Am79R100/101 Vs Am79R79 Device Comparison Brief

Vout_offset = (Vring – Vrref) x 100

For example, if yo u need 20 V DC offset at Vab duri ng the ring ing , appl y 200 mV DC differ e nce

between the Vring and the Rref pins.

Because of the input impedance variation, the resistor value will contribute some tolerance to the

offset output. One should measure the Voffset during ringing to decide upon a set of values.

For the voltage divider bias circuit, a 0.1 uf cap may be needed between the bias point and

ground to reduce the transient effect. Please note that the Rref and Vring inputs should not be

treated as regular op-amp inputs.

Figure 4 Ringing with Bias, Both VRING and RREF Pins

4. Legerity SLAC™ Device Interface

Traditionally the ringing signal is fed into the RSLIC device by separate external devices. Here we

are introducing a ringing source generated from a digital source through the PCM highway, such

as DSP. In order to pass a ringing frequency like 20hz, some filters in the QSLAC™ or ASLAC™

devices need to be adjusted. Within the SLAC™ device, the low-pass filter band limits the signal.

The R digital filters (IIR and FIR), need to be programmed to pass the lower frequency, AISN, and

the Z and B filters need to be turned off to stop the feedback between the Vout and Vin paths.

Gain in the receive path needs to be adjusted to meet the ring output requirement. To minimize

the changes, default settings were used where possible - only two commands need to be

changed: the Command [60/61] Wrd/Rd Operating Function and the Command [82/83] Wrt/Rd

GR filter Coeff. The le vel of the dig ital si gna l can also be adj us ted to sat isfy the ringi n g output

requirement.

QSLAC and ASLAC Device Settings for Ring Generation through the PCM Highway:

60 20 # Write Operating Functions: choose all the default

settings except for EGR = 1, and for programmed GR

filter = enabled.

82 0111 # Write GR Filter Coefficients: set Grain = 1.

0E # Activate

With the above filter settings at 20hz, a –0.4dbm0 sine wave signal on the PCM highway for the

QSLAC device, and a 1.8dbm0 sine wave signal on the PCM highway for the ASLAC device will

Am79R101 Device

Vring < 2 Vpk-pk

RR1

RR2

VRING

RREF

VCC

Vbias

Am79R100/101 Vs Am79R79 Device Comparison Brief 5

generate around 1.96Vp-p on the Vout pin. This Vout is enough for the RSLIC device to reach the

required ringing output. The data collected are based on the balance ringing configurations.

Please remember, after generating the ring, the filters need to be reconfigured for normal

transmission setup.

The bias source can also be connected from a Legerity SLAC device. Normally there is a Vref pin

on the Legerity QSLAC device (2.1V) or ASLAC device (2.1V) to provide the DC bias for the AC

coupled si gna l at the SLAC de vi ce in put and out put, but the cur rent driving ab ility is different

between the SLAC devices. For the QSLAC device, additional circuitry may be needed to

compensate for the driving problem. We use a positive buffer (OP27 from Analog Devices)

connected to Vref output to service 4 channels as reference voltage on the QSLAC device

evaluation board. Any low offset opamp will work depending on how heavy the load (please refer

to the manufacturing data sheet for multi-channel applications, and pay close attention to the

polarity). The ASLAC device has a 1mA driving ability, which should be enough for single channel

applications. (Figures 5 and 6)

Figure 5 DC Offse t Ring Interface with the QSLAC™ Device

Am79R101 Device

VRING

RREF1

QSLAC

Device VOUT

VREF

OP27

RR1

RR2

RREF2

RREF3

RREF4

5 V

PCM

High-

way

6 Am79R100/101 Vs Am79R79 Device Comparison Brief

Figure 6 DC Offse t Ring Interface with the ASLAC™ Device

Am79R101 Device

VRING

RREF

ASLAC

Device VOUT

VREF

RR1

RR2

PCM

High-

way

DC Feed For the majority of short loop applications, the total loop resistance is less than 1 kΩ. The

Am79R100 device increases the DC feed loop resistance with respect to the Am79R79 device Rldc

= 750 Ω (loop plu s ph on e ) to Rldc = 1250 Ω (loop plus phone) to deliver the same minimum 20

mA current when Rsgl is connected to ground (Vbat2 = –35 V). The extra 500 Ω loop resistance

is ≅6000 feet longer loop distance (26AWG). The constant current region on the Am79R100/101

devices is the same as the Am79R79 device. The data provided in this section, illustrates the DC

driving capacity. Note that the maximum loop length may create a problem for reliable ring-trip

detection.

Anti-Saturation Region

The Am79R100/101 devices default settings are different from the Am79R79 device. For the

Am79R79 device the Rsgl = open and the Rsgh = open, but for the Am79R100/101 devices,

the Rsgl = open and the Rsgh = ground. The DC feed curves are similar to each other, except that

the Am79R100/101 devices have more he adro om. I n the OH T mod e, th e on -h ook volt age was

lower ed f rom t ha t o f th e Am 7 9R79 dev ice. Va b = 49 V to Vab = 45 V. Wit h the Rs gl = g r ound , the

knee of t he low bat te ry an ti -s at e nt ry can be rais ed to 25 V from the nominal 12.5 V with Vbat2 =

−35 V. This increases the utilization of Vbat2, and is beneficial for caller ID applications. With the

appropriate Rsgh connection, the on-hook voltage can be adjusted for MTU and fax machine

application without violating the UL requirement.

The anti-sat calculation formula also changed. The following equations show the Am79R100/101

devices DC feed calculations derived using Mathcad:

Am79R100/101 Vs Am79R79 Device Comparison Brief 7

Am79R100 Device DC Feed Curve with New Formula

Rdc 100000 Vbat1 95 Vbat2 24 Il ..,

0 0.0001 0.06

Rl 600 (Rl = Rl + Rf, Rf = 0) Rsgl 1000000000

Low bat operation:

Vab .

2500

Rdc R

Constant-current

Vasl .

61.44()

125000 Rsgl

308000 .

4.92Rsgl Rsgl = open (1G Ω), =

Vasl 12.489

Vappl 4.17 Vasl Vappl with low battery, =

Vappl 16.659

Ilim 0.025 Constant current

l( )

Il Vappl .

4.17

Ilim Il Calculat ion formu la and curve

Vabl( )Il if( )

,,>

Il Ilim Ilim Vl()

Il Connect the curves

High bat operation:

Rsgh

Rsgh = ground default setting

Vash Vasl .

61.44 ()

101000 Rsgh

223000 .

4Rsgh Vash=40.316

Vapph 4.17 Vash =

Vapph 44.486

Vh( )

Il Vapph .

4.17

Ilim Il Calcu lation for mu la and curve

Vab2( )Il if( )

,,>

Il Ilim Ilim Vh( )Il Connect the curves

00.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04

Vabl ()

Vab2 ()

Il(A)

VAB(Volt)

8 Am79R100/101 Vs Am79R79 Device Comparison Brief

Ring Trip Because a high battery extends the driving ability for both ringing and off hook, we observe that

the loop length of the ring trip for the Am79R100/101 devices are increased compared to the

Am79R79 device. For the Am79R100 device, the recommended setup where Rrt1 = 604K, Rrt2 =

12K, Crt = 1 uf, CF = 1.26, allows Rloop to be extended to a maximum value of 1.1 kΩ with clear

ring trip. For the Am79R101 device, Rrt1 = 700K, Rrt2 = 12K, Crt = 1 uF, CF = 1.41 balance

ringing, the Rloop can reach a maxim um of 800 Ω. A small faulty pulse is allowed at the DET

output because most applications will apply debounce capability of typically 13ms, with 20hz

ringing. Debounce circuits will ignore the glitch at the DET output during the transition. There is a

hysteresis applied in both Am79R100/101 devices ring trip circuits to eliminate the threshold

uncertainty. The RC constant for Rrt2 and Crt is measured at less than 30 ms in the worse case

(different phase angle), where it will affect the system level ring-trip requirement and should be

kept as short as possible. If the time constant is too short, the DET will generate a lot of pulses

around the threshold, and the value may need to be adjusted with a particular application.

For DC offset ringing, the ring-trip current is smaller due to the limited swing. With the same value

setup, the ring-trip loop length is expected to be less than the balanced ringing. With 10 V DC

offset applied on the output during ringing, the Am79R101 device can easily ring the Nortel

Venture multi-line feature phone and Casio Phonemate series devices such as the TI-330, 9300.

UL To meet the fax mac hine an d ma intenan ce term ination units ( MTU ) r equire me nt, the SL IC

device needs to provide a higher on- ho ok voltag e min imum, –43 V. UL has specified that an y

DC voltage high er than 60 V is con sider ed h azardous and needs mor e string ent is olat ion

requirements. The Am79R1 00/101 dev ice s app ly a dio de cla mp tec hniqu e so th at the on- hoo k

high battery shou ld not e xce ed –5 4 V in Stand by mo de.

Protection Circuit

Because the supply voltage has increased from a nominal value of –75 V to –95 V, the pr ote ction

circuits we usually use have to move up for higher rating. There are two commonly used devices

for level two protection circuitsthe diode bridge plus the thyristor surge protector and the battery

tracking protection thyristor IC. If we use –70 V for the high battery, the maximum thyristor

breakover voltage must be specified not to exceed –70 V, whereas the minimum must not be less

than the maximum A-to-B line voltage (on hook). Therefore, the current is not sourced from the

SLIC device und er the norm al line co nd iti on. For the batt er y trac ki ng protection de vice, which can

be externally programmed by the battery, the minimum breakover is still greater than Vbat, so no

current will be drained during the normal operation. We suggest a Power Innovation

programmable over a voltage protection device, part number TISP61089A (maximum 100 V

limit), which is suitable for Am79R100/101 SLIC device application. Now, there is a TISP61089AS

for small outline SMT that is compliant with UL1950 requirements. The proposed small outline

pinout will be interchangeable with the LCP1521 from ST. The TECCOR BATTRAX P1001SC

protector is another recommended device for this application. In the bridge rectifier and thyristor

device combination application, the fast or ultra fast diodes are strongly recommended for

lightning protection. For details, please refer to the application note, PID# 080270A: Generic SLIC

Device Protection From Lightning Surges and AC Mains Power Cross.

Pinout Difference

Even though the Am79R100/101 devices are pin compatible functional replacements for the

Am79R79 device, there are some differences to note:

Pin Function Am79R79 Device Am79R100 Device Am79R101 Device

Pin 7 B2EN NC NC

Pin 16 NC NC RREF

Am79R100/101 Vs Am79R79 Device Comparison Brief 9

Unlike the Am79R79 device, the Am79R100/101 devices incorporate B2EN into the state

decoders, which eliminates an I/O control pin with auto battery selection. The following table

illu str ate s b atte r y select i on by ea ch state:

C3 C2 C1 State E1 = 1 E1 = 0 Battery

0 0 0 Open Circuit Ring Trip Ring Trip Vbat2

0 0 1 Ringing Ring Trip Ring Trip Vbat1

0 1 0 Active Loop Det. Ground Key Vbat2

0 1 1 On Hook TX (OHT) Loop Det. Ground Key Vbat1

1 0 0 Tip Open Loop Det. Ground Key Vbat1

1 0 1 Standby Loop Det. Ground Key Vbat1

1 1 0 Active Pol. Rev. Loop Det. Ground Key Vbat2

1 1 1 OHT Pol. Rev. Loop Det. Ground Key Vbat1

Additiona ll y, the Am 79R100/101 devi ce s Vb at1 decoupl ing ca ps , Cax, Cbx , and Chp vol tag e

ratings should have enough headroom compared to those of the Am79R79 device.

Power Dissipation

For a condensed linecard design, the power dissipation requirement is even tighter than before.

With a high supply battery, the unit can deliver more power to the load, but you do not want it to

consume more power than it has to. The following table shows the difference in typical power

consumption between devic es. Gener al ly sp eaking, The Am79R100/101 devi ce s con su me less

power than the Am79R79 device in Ringing mode.

Table 1 Power Dissipation Between the Am79R79/100/101 Devices, Using 75 V BAT1 and 24 V BAT2

State Am79R79 Device Am79R100/101 Devices Battery

Open Circuit 48 mW 34 mW Vbat2

Standby 55 mW 43 mW Vbat1

OHT 200 mW 180 mW Vbat1

OHT 300 Ω2 W 2.6 W Vbat1

Active 300 Ω550 mW 540 mW Vbat2

10 Am79R100/101 Vs Am79R79 Device Comparison Brief

The contents of this document are provided in connection wit h Legerity, I nc. products . Legerity makes no representations or warranties wi th

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Legerity’s products are not designed, intended, authorized or warranted for use as components in systems intended for surgic al impl ant i nto

the body, or in other applicati ons i ntended t o support or sustain life, or in any other application in which the failure of Legerity’s product could

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Legerity reserves the right to discontinue or make changes to its products at any time without notice.

Trademarks

Legerity, t he Legerity l ogo, and combi n ations thereof, and ASLAC, ISLAC, QSLAC, and SLAC are trademarks of Legerity, Inc.

Other product names used in this publication are for identification purposes only and may be trademarks of their respective companies.