AM79R79JC datasheet(10/20 Pages) AMD

10 / 20 page

Am79R79 Data Sheet

Notes:

1. Unless otherwise noted, test conditions are BAT1 = –75 V, BAT2 = –24 V, VCC = +5 V, VNEG = –5 V, RL = 600 Ω,

RDC1 = 80 kΩ, RDC2 = 20 kΩ, RD = 75 kΩ, no fuse resistors, CHP = 0.018 µF, CDC = 1.2 µF, D1 = D2 = 1N400x,

two-wire AC input impedance (ZSL) is a 600

Ω resistance synthesized by the programming network shown below.

RSGL = open, RSGH = open, RDCR = 2 kΩ, RRT1 = 430 kΩ, RRT2 = 12 kΩ, CRT = 1.5 µF, RSLEW = 100 kΩ, CSLEW = 0.33 µF.

2. a. Overload level is defined when THD = 1%.

b. Overload level is defined when THD = 1.5%.

3. Balance return signal is the signal generated at VTX by VRX. This specification assumes that the two-wire AC load impedance

matches the programmed impedance.

4. Not tested in production. This parameter is guaranteed by characterization or correlation to other tests.

5. This parameter is tested at 1 kHz in production. Performance at other frequencies is guaranteed by characterization.

6. Group delay can be greatly reduced by using a ZT network such as that shown in Note 1 above. The network reduces the

group delay to less than 2 µs and increases 2WRL. The effect of group delay on linecard performance may also be compensated

for by synthesizing complex impedance with the QSLAC or DSLAC device.

7. 70 Vpk provides 50 Vrms with a crest factor of 1.25 to a load of 1400

Ω with 2 • Rf = 100, and Rline = 70 Ω (1570 Ω).

8. Open Circuit VAB can be modified using RSGH.

9. RD must be greater than 56 kΩ. Refer to Table 2 for typical value of RLTH.

10. Lower power is achieved by switching into low-battery state in standby. Standby loop current is returned to VBAT1 regardless

of the battery selected.

Notes:

* Only –1 and –2 performance grade devices support polarity reversal.

** For correct ground-start operation using Tip Open, VBAT1 on-hook battery must be used.

Table 1. SLIC Decoding

(DET) Output

State

C3 C2 C1

2-Wire Status

E1 = 1

E1 = 0

Battery Selection

Open Circuit

Ring trip

B2EN

Ringing

Ring trip

Active

Loop detector

Ground key

On-hook TX (OHT)

Loop detector

Ground key

Tip Open

Loop detector

Ground key

B2EN = 1**

Standby

Loop detector

Ground key

VBAT1

Active Polarity Reversal

Loop detector

Ground key

B2EN

OHT Polarity Reversal

Loop detector

Ground key

RT2 = 150 k

Ω

CT1 = 60 pF

RT1 = 150 k

Ω

VTX

RSN

VRX

RRX = 300 k

Ω

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