MH88612BV-K
Subscriber Line Interface Circuit (SLIC)
Data Sheet
Features
•
•
•
•
•
•
•
•
•
Transformerless 2-wire to 4-wire conversion
Battery and ringing feed to line
Off-hook and dial pulse detection
Ring ground over-current protection
Constant current feed with constant voltage
foldover
Relay driver
Power Denial
Wide Operating Range
Pin for pin compatible 600R and 900R variants
•
Control Systems
Ordering Information
MH88612BV-K1 20 Pin SIL*
*Pb Free Matte Tin
0°C to 70°C
Boxed
August 2006
Description
The SLIC provides a complete interface between a
switching system and a subscriber loop. Functions
provided include battery feed and ringing feed to the
subscriber line, 2-Wire to 4-Wire hybrid interfacing,
constant current feed with constant voltage foldback,
and dial pulse detection. The device is fabricated using
thick film hybrid technology in a 20-pin single in-line
package.
Applications
Line interface for:
•
•
•
PABX
Intercoms
Key Telephone Systems
LPGND
VBAT PD VCC VEE AGND
Constant
Voltage
Foldback
Power
Management
TF
TIP
RING
RF
Current and
Voltage
Sensing
2-Wire to
4-Wire
Conversion
VR
VX
RV
VRLY
Over Current
Protection
Relay
Drive
Circuit
Constant
Current
Feed
Loop
Supervision
CAP
RC
RD
CD
SHK
Figure 1 - Functional Block Diagram
1
Zarlink Semiconductor Inc.
Zarlink, ZL and the Zarlink Semiconductor logo are trademarks of Zarlink Semiconductor Inc.
Copyright 1999-2006, Zarlink Semiconductor Inc. All Rights Reserved.
MH88612BV-K
Data Sheet
TF
LPGND
VR
IC
VEE
AGND
PD
VX
TIP
RING
RF
VCC
RC
RD
RV
VRLY
CD
VBAT
CAP
SHK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Figure 2 - Pin Connections
Pin Description
Pin#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Name
TF
LPGND
VR
IC
VEE
AGND
PD
VX
TIP
RING
RF
VCC
RC
RD
RV
Description
Tip Feed.
Connects to external diode for protection
Loop Ground.
Is the system ground reference with respect to V
BAT.
Normally connected to
AGND.
Voice Receive (Input).
The 4 wire analog signal to the device.
Internal Connection.
No connection should be made to this pin
Negative Power Supply Voltage (-5 V).
Analog Ground.
Connects to System Ground (Earth).
Power Denial (Input).
A logic high will isolate the battery voltage to Tip/Ring.
Voice Transmit (Output).
The 4-wire analog signal from the device.
Tip Lead.
Connects to the "Tip" lead of the telephone line.
Ring Lead.
Connects to the "Ring" lead of the telephone line.
Ring Feed (Input).
Normally connected to Ring relay for negative battery feed voltage and ringing
voltage input.
Positive Power Supply Voltage (+5 V).
Relay Control (Input).
Active high.
Relay Drive.
Open collector sinks current when RC is at logic high.
Ring Feed Voltage.
Normally connected to pin 11 (RF) through a normally closed relay and to
external diode protection.
2
Zarlink Semiconductor Inc.
MH88612BV-K
Pin Description
Pin#
16
17
18
19
20
Name
VRLY
CD
VBAT
CAP
SHK
Relay voltage Supply (+5 V).
Clamping Diode.
Normally connected to AGND.
Description
Data Sheet
Negative Battery Feed Supply Voltage (-48 V).
Battery supply for the Subscriber Line. Typically
-48VDC is applied to this pin.
Ring Trip Filter Capacitor.
Normally connected via an external capacitor to ground to prevent
false ring trip. Must be open circuit to allow dial pulse detection.
Switch Hook Detect (Output).
A logic level 1 will indicate that the Subscriber Line is in the ’Off-
Hook’ state.
Note 1: C4 in Figure 3 can be added permanently to this pin for certain dial pulse applications.
Functional Description
The SLIC performs a transformerless 2-wire to 4-wire conversion of the analog signal. The 2-wire circuit is the
balanced line going to the subscriber loop, while the 4-wire circuit is the audio signal going to and from devices
such as the voice codec or switching circuit. The SLIC also provides a switch hook (SHK) status output which goes
high when the telephone is set off-hook.
Constant Current Feed
The MH88612BV-K family employs complex feedback circuits to supply a constant current feed or, if necessary,
constant voltage feed to the line. With a nominal -48 V battery the device will supply a constant current of typically
25 mA to a line up to 1100
Ω.
For longer lines there is insufficient battery voltage so the device automatically
switches to constant voltage mode where Tip and Ring will stay at their minimum and maximum voltage levels and
the supplied current will be reduced accordingly. The maximum line resistance supported is 2000
Ω
including the
telephone set.
Switch Hook Detection
The SHK pin will go to logic 1 to indicate that a telephone connected to the line has gone off-hook (on-line). Off-
hook will not be indicated if the loop resistance (including the telephone set) is too high for the device to support.
The SHK output will toggle to indicate dial pulses on the line. If the capacitor on CAP (Pin 19) has not been
switched out of circuit the dial pulses will be distorted.
Ringing And Ring Trip Detection
In Figure 3 a ringing signal (e.g.,90 Vrms and -48Vdc) is applied to the line by disconnecting pin 15 (RV) from pin
11(RF), and connecting the ringing voltage at pin 11 (RF) by use of the relay K1.
The SLIC can detect an off-hook condition during ringing but there is a large AC component which must be filtered
out to give a true off-hook condition at SHK.
A 1.0
µF
capacitor connected from pin 19 (CAP) to ground will provide adequate attenuation when ringing is
applied. Once an off-hook condition has been detected a logic low should be applied to pin 13 (RC) which will
deactivate the relay (K1) to disconnect the ringing voltage from pin 11 and reconnect to pin 15. At that time the SLIC
will revert to constant current feed operation.
3
Zarlink Semiconductor Inc.
MH88612BV-K
Data Sheet
For applications requiring Dial Pulse Detection the Capacitor connection to ground C1 should be controlled such
that the capacitor is disconnected during Pulse Dialling.
If the signalling method is unknown, a capacitor of approximately 56 nf should be permanently fitted between CAP
(pin 19) and ground. This should be in addition to the capacitor mentioned in the above paragraph.
During off-hook conditions (on-line), the capacitor (C1) should not have a low impedance path to ground. This can
be achieved using a transistor (Q1) and resistor (R2) as shown in Figure 3, with R2 providing a high impedance
path for C1. When ringing is applied (RC = 5V) the transistor will short circuit R2 which will give C1 a low impedance
path to ground and provide the required filtering.
Other methods can be used to switch out C1, such as a relay or a codec system drive output (with a similar
configuration as above).
For applications using DTMF signalling, C1 can be permanently connected to ground.
Current Limit
The Tip or Ring of the telephone line may accidentally be shorted to ground. In such a case, current will only flow through
the feed resistor. This high current will be sensed and reduced by the current limit circuit to a lower value to protect the
internal circuitry.
Power Denial
The power denial function is a feature of the MH88612 which allows for powering down of the subscriber loop. A
logic high voltage applied to the power denial input effectively removes the battery voltage from the loop driver
circuitry. The resulting I
LOOP
is negligible and power consumption is minimized. The power denial function is useful
for disabling a loop which may have a ground fault.
4
Zarlink Semiconductor Inc.
MH88612BV-K
R1
K1
VBAT
Data Sheet
11 RF
D4
D3
MH88612BV-K
3
~
-
+
90 VRMS
48V
D2
D1
1 TF
RV
15
2
9
LPGND
VR
VX
8
TIP
TIP
Protection
Circuit
SHK
20
RING
10 RING
13
RC
+5V
C2
K1
14
RD
16
VRLY
CAP
PD
7
19 C1
Q1
R3
R4
RC
-+
C4
R2
17 CD
VBAT VCC
18
C3
-48V
+5V
-5V
12
VEE
5
AGND
6
(Pin 13)
Component List
R1
R2
R3, R4
C1
C2, C3
D1,D2, D3, D4
Q1
K1
C4
200Ω + 10%, 1/4W
470kΩ + 5%, 1/4W
10kΩ + 5%, 1/4W
1.0µF, + 10%, 25V electrolytic capacitor
0.1µF, + 20%, 50V ceramic de-coupling capacitors
Diode rectifier 200V, 1A, IN4003
General purpose switching transistor
Relay E/M, 5V or 6V, 1 Form C
10nF - 56nF 20% 16V capacitor
= earth = ground
Protection Circuit - Depending on the application the Protection circuit may need to provide
over-voltage and/or over-current protection. In certain circumstances no protection will be required.
Figure 3 - Typical Application Circuit
5
Zarlink Semiconductor Inc.
京公网安备 11010802033920号
EEWORLD
