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參數(shù)資料
| 型號(hào)： | HC5515CMZ |
| 廠商： | Intersil |
| 文件頁數(shù)： | 4/20頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC SLIC ITU CO/PABX LP 28-PLCC |
| 標(biāo)準(zhǔn)包裝： | 925 |
| 功能： | 用戶線路接口概念（SLIC） |
| 電路數(shù)： | 1 |
| 電源電壓： | 4.75 V ~ 5.25 V |
| 功率（瓦特）： | 1.5W |
| 工作溫度： | 0°C ~ 70°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 28-LCC（J 形引線） |
| 供應(yīng)商設(shè)備封裝： | 28-PLCC（11.51x11.51） |
| 包裝： | 管件 |
| 包括： | 可編程回路電流檢測(cè)器，振鈴?fù)禉z測(cè)器，熱關(guān)機(jī) |
12
FN4235.6
June 6, 2006
Cases 2 and 3 illustrate the longitudinal loop current. The
definition of a longitudinal loop current is a common mode
current, that flows either out of or into tip and ring
simultaneously. Longitudinal currents in the on-hook state result
in equal currents flowing through the sense resistors R1 and
R2 (Figure 17). And longitudinal currents in the off-hook state
result in unequal currents flowing through the sense resistors
R1 and R2. Notice that for case 2, longitudinal currents flowing
away from the SLIC, the current through R1 is the metallic loop
current plus the longitudinal current; whereas the current
through R2 is the metallic loop current minus the longitudinal
current. Longitudinal currents are generated when the phone
line is influenced by magnetic fields (e.g., power lines).
Loop Current Detector
Figure 17 shows a simplified schematic of the loop current
detector. The loop current detector works by sensing the
metallic current flowing through resistors R1 and R2. This
results in a current (IRD) out of the transconductance
amplifier (gm1) that is equal to the product of gm1 and the
metallic loop current. IRD then flows out the RD pin and
through resistor RD to VEE. The value of IRD is equal to:
The IRD current results in a voltage drop across RD that is
compared to an internal 1.25V reference voltage. When the
voltage drop across RD exceeds 1.25V, and the logic is
configured for loop current detection, the DET pin goes low.
The hysteresis resistor RH adds an additional voltage
effectively across RD, causing the on-hook to off-hook
threshold to be slightly higher than the off-hook to on-hook
threshold.
Taking into account the hysteresis voltage, the typical value
of RD for the on-hook to off-hook condition is:
Taking into account the hysteresis voltage, the typical value
of RD for the off-hook to on-hook condition is:
A filter capacitor (CD) in parallel with RD will improve the
accuracy of the trip point in a noisy environment. The value
of this capacitor is calculated using the following Equation:
where: T = 0.5ms.
Ring Trip Detector
Ring trip detection is accomplished with the internal ring trip
comparator and the external circuitry shown in Figure 18.
The process of ring trip is initiated when the logic input pins
are in the following states: E0 = 0, C1 = 1 and C2 = 0. This
logic condition connects the ring trip comparator to the DET
output, and causes the Ringrly pin to energize the ring relay.
The ring relay connects the tip and ring of the phone to the
external circuitry in Figure 18. When the phone is on-hook
the DT pin is more positive than the DR pin and the DET
output is high. For off-hook conditions DR is more positive
than DT and DET goes low. When DET goes low, indicating
that the phone has gone off-hook, the SLIC is commanded
by the logic inputs to go into the active state. In the active
state, tip and ring are once again connected to the phone
and normal operation ensues.
Figure 18 illustrates battery backed unbalanced ring injected
ringing. For tip injected ringing just reverse the leads to the
phone. The ringing source could also be balanced.
NOTE: The DET output will toggle at 20Hz because the DT input is
not completely filtered by CRT. Software can examine the duty cycle
and determine if the DET pin is low for more that half the time, if so
the off-hook condition is indicated.
I
RD
I
TIP
I
RING
–
600
------------------------------------
I
L
300
----------
==
(EQ. 24)
R
D
465
I
ON
HOOK to OFF
–
HOOK
–
--------------------------------------------------------------------------
=
(EQ. 25)
R
D
375
I
OFF
HOOK to ON
–
HOOK
–
--------------------------------------------------------------------------
=
(EQ. 26)
C
D
T
R
D
--------
=
(EQ. 27)
HC5515
DET
RD
R2
gm1
gm1(IMETALLIC)
RD
CD
VREF
+
-
CURRENT
LOOP
VEE
-5V
IRD
RH
RING
TIP
+
-
R1
+
-
CASE 1
CASE 2
CASE 3
IMETALLIC
←
ILONGITUDINAL
←
ILONGITUDINAL
→
COMPARATOR
DIGITAL MULTIPLEXER
1.25V
+
-
FIGURE 17. LOOP CURRENT DETECTOR
HC5515
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