HC-5524 Datasheet, PDF (5/9 Pages) Intersil Corporation – EIA/ITU 24V PABX SLIC with 25mA Loop Feed

HC-5524
Pin Descriptions (Continued)
SOIC PLCC SYMBOL
DESCRIPTION
14
22
TIP
An analog input connected to the TIP (more positive) side of the subscriber loop through a feed resistor and
ring relay contact. Functions with the RING terminal to receive voice signals from the telephone and for loop
monitoring purposes.
15
24
RING An analog input connected to the RING (more negative) side of the subscriber loop through a feed resistor.
Functions with the TIP terminal to receive voice signals from the telephone and for loop monitoring purposes.
16
25
RFS
Ring Feed Sense - Senses RING side of the loop for Ground Key Detection. During Ring injected ringing the
ring signal at this node is isolated from RF via the ring relay. For Tip injected ringing, the RF and RFS pins must
be shorted.
17
27
V_RX
Receive Input, 4-Wire Side - A high impedance analog input. AC signals appearing at this input drive the Tip
Feed and Ring Feed amplifiers differentially.
18
31
C₂
Capacitor #2 - An external capacitor to be connected between this terminal and ground. It prevents false ring
trip detection from occurring when longitudinal currents are induced onto the subscriber loop from power lines
and other noise sources. This capacitor should be nonpolarized.
19
32
V_TX
Transmit Output, 4-Wire Side - A low impedance analog output which represents the differential voltage across
TIP and RING. Transhybrid balancing must be performed beyond this output to completely implement two to
four wire conversion. This output is referenced to analog ground. Since the DC level of this output varies with
loop current, capacitive coupling to the next stage is necessary.
20
33
PRI
A TTL compatible input used to control PR. PRI active High = PR active low.
21
34
PR
An active low open collector output. Can be used to drive a Polarity Reversal Relay.
22
35
DG
Digital Ground - To be connected to zero potential. Serves as a reference for all digital inputs and outputs on
(Note 4) the SLIC.
23
36
RD
Ring Relay Driver - An active low open collector output. Used to drive a relay that switches ringing signals onto
the 2-Wire line.
24
37
V_FB
Feedback input to the tip feed amplifier; may be used in conjunction with transmit output signal and the spare
(Note 5) op-amp to accommodate 2-Wire line impedance matching. (This is not used in the typical applications circuit).
25
38
NA
39
26
41
TF₂
Tip Feed - A low impedance analog output connected to the TIP terminal through a feed resistor. Functions
with the RF terminal to provide loop current, and to feed voice signals to the telephone set and to sink longitu-
dinal currents. Must be tied to TF₁.
TF₁
Tie directly to TF₂ in the PLCC application.
RF₁
Ring Feed - A low impedance analog output connected to the RING terminal through a feed resistor. Functions
with the TF terminal to provide loop current, feed voice signals to the telephone set, and to sink longitudinal
currents. Tie directly to RF2.
NA
42
RF₂
Tie directly to RF₁ in the PLCC application.
27
43
V_B-
The battery voltage source. The most negative supply.
28
44
BG
Battery Ground - To be connected to zero potential. All loop current and some quiescent current flows into this
(Note 4) ground terminal.
1, 5, 6, 7,
14, 15,
16, 21,
23, 26,
28, 29,
30, 40
NC
No internal connection.
NOTES:
4. All grounds (AG, BG, and DG) must be applied before V_B+ or V_B-. Failure to do so may result in premature failure of the part. If a user wishes
to run separate grounds off a line card, the AG must be applied first.
5. Although not used in the typical applications circuit, V_FB may be used in matching complex 2-Wire impedances.
5