- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄384393 > HC5517 (Intersil Corporation) 3 REN Ringing SLIC For ISDN Modem/TA and WLL PDF資料下載
參數(shù)資料
| 型號： | HC5517 |
| 廠商： | Intersil Corporation |
| 英文描述： | 3 REN Ringing SLIC For ISDN Modem/TA and WLL |
| 中文描述： | 3任振鈴用戶接口對于ISDN調(diào)制解調(diào)器/電訊和WLL |
| 文件頁數(shù)： | 6/18頁 |
| 文件大小： | 175K |
| 代理商： | HC5517 |
65
Circuit Operation and Design Information
The HC5517 is a voltage feed current sense
S
ubscriber
L
ine
I
nterface
C
ircuit (SLIC). This means that for long loop appli-
cations the SLIC provides a constant voltage to the tip and
ring terminals while sensing the tip to ring current. For short
loops, where the loop current limit is exceeded, the tip to ring
voltage decreases as a function of loop resistance.
The following discussion separates the SLIC’s operation into
its DC and AC path, then follows up with additional circuit
design and application information.
DC Operation of Tip and Ring Amplifiers
SLIC in the Active Mode
The tip and ring amplifiers are voltage feedback op amps
that are connected to generate a differential output (e.g. if tip
sources 20mA then ring sinks 20mA). Figure 1 shows the
connection of the tip and ring amplifiers. The tip DC voltage
is set by an internal +2V reference, resulting in -4V at the
output. The ring DC voltage is set by the tip DC output volt-
age and an internal V
BAT
/2 reference, resulting in V
BAT
+4V
at the output. (See Equation 1, Equation 2 and Equation 3.)
Current Limit
The tip feed to ring feed voltage (Equation 1 minus
Equation 3) is equal to the battery voltage minus 8V. Thus,
with a 48 (24) volt battery and a 600
loop resistance,
including the feed resistors, the loop current is 66.6mA
(26.6mA).
On
short
loops
approaches zero and the need exists to control the
maximum DC loop current.
the
line
resistance
often
Current limiting is achieved by a feedback network (Figure 1)
that modifies the ring feed voltage (V
D
) as a function of the
loop current. The output of the Transversal Amplifier (TA) has
a DC voltage that is directly proportional to the loop current.
This voltage is scaled by R
10
and R
28
. The scaled voltage is
the input to a transconductance amplifier (GM) that
compares it to an internal reference level. When the scaled
voltage
exceeds
the
internal
transconductance amplifier sources current. This current
charges C
16
in the positive direction causing the ring feed
voltage (V
D
) to approach the tip feed voltage (V
C
). This
effectively reduces the tip feed to ring feed voltage (V
T-R
),
and holds the maximum loop current constant.
reference
level,
the
The maximum loop current is programed by resistors R
10
and R
28
as shown in Equation 4 (Note: R
10
is typically
100k
).
Figure 2 illustrates the relationship between V
T-R
and the
loop resistance. The conditions are shown for a battery volt-
age of -24V and the loop current limit set to 25mA. For a infi-
nite loop resistance both tip feed and ring feed are at -4V
and -20V respectively. When the loop resistance decreases
from infinity to about 640
the loop current (obeying Ohm’s
Law) increases from 0mA to the set loop current limit. As the
loop resistance continues to decrease, the ring feed voltage
approaches the tip feed voltage as a function of the pro-
gramed loop current limit (Equation 4).
V
TIPFEED
V
C
2V
–
-----------
4V
–
=
=
=
(EQ. 1)
V
RINGFEED
V
D
V
--------------
1
R
R
---
+
V
TIPFEED
–
=
=
(EQ. 2)
V
RINGFEED
V
D
V
BAT
4
+
=
=
(EQ. 3)
FIGURE 1. OPERATION OF THE TIP AND RING AMPLIFIERS
V
RX
OUT1
V
RING
V
BAT
2
-
+
+
-
V
C
V
D
R
14
R
12
R
11
R
13
90k
90k
R
R/20
R
R/2
TIP FEED
RING FEED
V
OUT1
, V
RX
GROUNDED FOR
DC ANALYSIS
TIP
RING
TRANSVERSAL
AMP
+
-
V
TX
R
10
R
28
RF2
GM
C
16
90k
INTERNAL
+2V REF
+
+
-
R
TA
+
-
+
-
+
-
I
LIMIT
0.6
---------------------------------------------
(
)
R
28
R
+
(
)
=
(EQ. 4)
0
-25
-20
-15
-10
-5
0
LOOP RESISTANCE (
)
CONSTANT VOLTAGE
REGION
T
∞
FIGURE 2. V
T-R
vs R
L
(V
BAT
= -24V,
I
LIMIT
= 25mA
)
250
500
750
V
RING FEED
= -20V
V
TIP FEED
= -4V
CURRENT LIMIT
REGION I
LOOP
= 25mA
HC5517
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| HC5517CB | 3 REN Ringing SLIC For ISDN Modem/TA and WLL |
| HC5517CM | 3 REN Ringing SLIC For ISDN Modem/TA and WLL |
| HC5517IM | 3 REN Ringing SLIC For ISDN Modem/TA and WLL |
| HC5517IB | GIGATRUE 550 CAT PATCH CBL NO BOOT 6FT RD 25 PK |
| HC55180 | Extended Reach Ringing SLIC Family |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| HC5517_00 | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:3 REN Ringing SLIC For ISDN Modem/TA and WLL |
| HC55171 | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:5 REN Ringing SLIC for ISDN Modem/TA and WLL |
| HC55171_03 | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:5 REN Ringing SLIC for ISDN Modem/TA and WLL |
| HC55171B | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| HC55171BEVAL-TRAP1 | 制造商:Harris Corporation 功能描述: |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。