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(R)
MH88612K
Subscriber Line Interface Circuit Preliminary Information
Features
* * * * * * * * * * Input impedance 600 Transformerless 2-wire to 4-wire conversion Battery and ringing feed to line Off-hook and dial pulse detection Ring ground over-current protection Adjustable constant current feed Relay drive output with diode protection Power Denial Wide V BAT Operating Range Tip/Ring Reversal
MH88612K
ISSUE 3
April 1995
Ordering Information
30 Pin SIL Package
0C to 70C
Description
The SLIC provides a complete interface between a switching system and subscriber loop. Functions provided include battery feed, ringing feed and tipring reversal to the subscriber line, 2-Wire to 4-Wire hybrid interfacing, constant current feed and dial pulse detection. The device is fabricated as a thick film hybrid using various technologies.
Applications
Line interface for: * PABX * * * Intercoms Key Telephone Systems Control Systems
LPGND RF TF TIP RING T/R Reverse
VBat
PD
VDD VEE GNDA
Power Denial Battery Feed 2-Wire to 4-Wire Conversion
VR VX
RC2
T/R Reverse Relay Driver
Over Current Protection
VRLY RD1 RC1 Relay Drive Circuit
Constant Current Feed
Loop Supervision
VRef CAP
RV
SHK
Figure 1 - Functional Block Diagram
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MH88612K
TF RF IC IC IC IC IC TIP IC RING RC2 LPGND IC VR VRef CAP SHK GNDA VEE VDD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 TF VBat RV PD VX IC IC VRLY RC1 RD1
Preliminary Information
21 22 23 24 25 26 27 28 29 30
Figure 2 - Pin Connections
Pin Description
Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Name TF RF IC/NC IC/NC IC/NC IC/NC IC/NC TIP IC/NC RING RC2 LPGND IC/NC VR VRef Description Tip Feed. Connects to external diode for protection. Internally connected to pin 21. Ring Feed (Input). is normally connected to ring relay for negative battery feed voltage and ringing voltage input. No Connections to be made to this pin, used for internal connection. No Connections to be made to this pin, used for internal connection. No Connections to be made to this pin, used for internal connection. No Connections to be made to this pin, used for internal connection. No Connections to be made to this pin, used for internal connection. Connects to the "Tip" lead of the telephone line. No Connections to be made to this pin, used for internal connection. Connects to the "Ring" lead of the telephone line. Relay Control 2 (Input). Active high to reverse Tip/Ring. Loop Ground is the system ground reference with respect to VBat. Normally tied with GNDA. No Connections to be made to this pin, used for internal connection. Voice Receive (Input) is the 4-wire analog signal to the SLIC. Voltage Reference (Input). to set the constant current feed to the subscriber line. Constant current feed can be adjusted by the input voltage on the VRef. This pin can also be grounded for normal 25mA loop current. Connects external capacitor to ground for ring trip. Switch Hook Detect (Output). Active high Analog Ground (0V) Negative Power Supply Voltage (-5V). Positive Power Supply Voltage (+5V). Tip Feed. Connect an external diode for protection. Internally connected to pin 1. Negative Battery Feed Supply Voltage (-48V).
16 17 18 19 20 21 22
CAP SHK GNDA VEE VDD TF VBat
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Preliminary Information
Pin Description (Continued)
Pin # 23 24 25 26 27 28 29 30 Name RV PD Vx IC/NC IC/NC VRLY RC1 RD1 Description
MH88612K
Ring Feed Voltage connects to (RF) through a normally closed ring relay. Power Denial (Input). A logic high will isolate the battery voltage to tip/ring. Voice Transmit (Output). is the 4-wire analog signal from the SLIC. No connections to be made to this pin, used for internal connection. No connections to be made to this pin, used for internal connection. Relay Voltage Supply (+5V). This pin is used to power the on board relay. Relay Control 1 (Input). Active high. Normally used for ringing. Open collector sinks current when RC1 is at logic high.
Functional Description
The SLIC performs a transformerless 2-wire to 4wire 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.
use of the relay K1. An internal clamp diode is provided between VRLY and RD1. 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 1.0F capacitor connected from (Cap) to ground will provide adequate attenuation when ringing is applied. Once an off-hook condition has been detected a logic high should be applied to (RC) which will activate the relay (K1) to disconnect the ringing voltage from (RF) and reconnect to (RV). At that time SLIC will revert to constant current feed operation. For applications requiring Dial Pulse Detection the Capacitor connection to ground should be controlled such that the capacitor is only connected during ringing. During off-hook conditions (closed loop), the capacitor should be switched out. This can be performed using a transistor, relay to system drive output of a codec. Applying GNDA to the Ring Trip Filter Control pin will switch in the filter, whilst removing GNDA, (with the switch in a tristate condition), will switch out the filter. For applications using DTMF signalling, the capacitor can be permanently connected to ground.
Constant Current Feed
The SLIC employs a complex feedback circuit to supply a constant feed current to the line. This is done by sensing the sum of the voltages across the internal feed resistors and comparing it to an input reference voltage (VRef) that determines the constant feed current. If VREF is externally grounded, the constant current is set at 25mA. For a constant current setting between 18mA and 30mA. VRef can be set between 8.75 Vdc and -6.35 Vdc. The relationship is defined by the equation: ILoop = 25 - V Ref mA (2 mA) 1.25
Switch Hook Detection
When the DC current exceeds an internal threshold level, the switch hook (SHK) will go high. If the loop resistance is so high that V BAT can no longer supply the required amount of loop current as determined by constant current supply circuit, the output of the switch hook (SHK) will go low to indicate that the loop resistance is too high and the line is on hook.
Tip/Ring Reverse
The MH88612K provides a Tip/Ring reversal relay driver. To activate the internal relay to reversal Tip and Ring apply a logic input to RC2.
Current Limit Ringing And Ring Trip Detection
In Figure 3 a ringing signal (e.g., 90 Vrms +-48 Vdc is applied to the line by disconnecting (RV) from (RF), and connecting the ringing voltage at (RF) by The Tip or Ring may be accidentally shorted to ground. In such a case, current will only flow through the feed resistor. This high current will be sensed
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MH88612K
and reduced by the current limit circuit to a lower value to protect the internal circuitry.
Preliminary Information
subscriber loop. A logic high input applied to the power denial pin effectively removes the battery voltage from the loop driver circuitry. The resulting ILoop is negligible and power consumption is minimised. The power denial function is useful for disabling a loop which may have a ground fault. This pin should be held low when not in use.
Receive Gain
The power denial function is a feature of the MH88612C which allows for powering down of the
Applications
Component List R1 = 1/4 W, + 10%, 200 R2 = 1/4 W, + 5%, 470 C1 = Cap. elec., 1.0F, + 10%, 25V D1,D2,D3,D4 = Diode Rect., 200V, 1A, IN4003 K1 = Relay E/M, 5 or 6V, 1 form C Decoupling capacitors (Cap. Cer 0.1F, 50% + 20%) should be added to V DD, V EE, VBat, VRef and V RLY Options RV1, RV2 = 160V Vrms, 250V, 10J
90 VRMS SUPERIMPOSED ON -48VDC
R1
K1
VBat
MH88612K
RF VR RV
D4 D1 D2
VX TF
D3
VRef
VBat Tip RV1
TIP
SHK
RV2 Ring
RING RC2 RC1
PD
+5V
K1
VRLY
C1
RD1 VBat VDD VEE
CAP GNDA +
R2
Ring Trip Filter Control
-48V +5V
-5V
Figure 3 - Application Circuit
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Preliminary Information
Absolute Maximum Ratings*
Parameter 1 DC Supply Voltage Symbol VDD VEE VBat TSTG PD Min -0.3 +0.3 0.3 -40 Max +15 -15 -60 100 2
MH88612K
Units V V V C W
2 3
Storage Temperature Package Power Dissipation
* Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied.
Recommended Operating Conditions
Characteristics 1 Operating Supply Voltage Sym VDD VEE VRef VBat VRLY 2 Operating Temperatures TO 0 -27 Min 4.75 -4.75 Typ 5.0 -5.0 0 -48 5 70 -60 Max 5.25 -5.25 Units V V V V V C Adjustable Comments
Typical figures are at 25C and are for design aid only.
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MH88612K
Characteristics 1 Supply Current VDD VEE VBat 2 3 4 Power Consumption Constant Current Line Feed Adjustable Loop Current Range Operating Loop Resistance Ring Ground Over-Current IDD IEE IBAT PC ILoop ILoop 23 18 5.8 -2.6 210 1410 25 27 30 500 mA mA A mW mW mA mA Sym Min Typ Max
Preliminary Information
DC Electrical Characteristics* - Voltages are with respect to GNDA unless otherwise stated.
Units Test Conditions
PD = Logic high Standby Active VRef = GNDA, V Bat = -48V Adjustable with Ext. VRef Input, VBat = -48V VBat = -28V @ ILoop = 18mA, R Loop includes telephone set
5
RLoop
1200
6
Protection Off-Hook Detect Output Low Voltage (On-hook) Output High Voltage (Off-hook) Off- Hook Detect Output Low Current (on-hook) Input High Current. (off-Hook) RC1,RC2, PD Control Inputs Input Low Volt. (no activation) Input High Volt. (activation) RC1, RC2, PD control Inputs Input Low Current (no activation) Input high current (activation)
40
mA
7
Active high logic VOL VOH 0 2.7 0.4 5.25 V V
8
IOL IOH VIL VIH IIL IIH
8 -400 0.7 2.0 -50 50
mA A Active high logic V V A A
9
10
* DC Electrical Characteristics are over recommended operating supply voltages. Typical figures are at 25C with nominal 5V supplies and are for design aid only.
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Preliminary Information
AC Electrical Characteristics
Characteristics 1 2 3 4 5 6 7 Ringing Voltage Ringer Equivalence Number Ring Trip Detect time Input AC Impedance 2-wire Input Impedance at VR Output Impedance at Vx Gain 2-wire to Vx Gain relative to Gain @ 1kHz 8 Gain VR to 2-wire Gain relative to Gain @ 1kHz 9 2-wire Return Loss over 300-3400Hz Transhybrid Loss over 300-3400 Hz Longitudinal to Metallic Balance Total Harmonic Distortion at Vx at Tip and Ring 13 Common Mode Rejection Ratio 2-wire to Vx Idle channel Noise (at Vx) Power supply rejection ratio VDD VEE VBAT CMRR 40 THD THL 20
Zin
MH88612K
Sym VRING REN 100 600 100 10 -1.0 +0.1 -1.0 +0.25 30 dB dB dB (Input 1.0 Vrms 1kHz at VR ZLoad = 600 300-3400 Hz) Input 0.5 Vrms 1kHz across Tip and Ring, ZLoad = 600 Input 0.5V Vrms at VR ZLoad = 600 Input 0.5 Vrms Input 3dBm, 1 kHz across Tip and Ring, Input 1.0 Vrms 1kHz at VR Input 0.5 Vrms, 1KHz Min 40 17 Typ* 80 Max 110 25 3 125 ms k dB Input 3 dBm, 1kHz across Tip and Ring, 300-3400 Units Vrms Hz Test Conditions Superimposed on VBAT = -48V
10 11 12
35 50
50 55 0.1 1.0
dB dB %
0.1 50
1.0
% dB
14 15
Nc PSRR 30 30 30 35 40 60
12
dBrnC
C- Message
dB dB dB
1 VPP ripple, 1kHz on VDD VEE, VBAT, measure at Vx and across Tip and Ring
* Typical figure are at 25C and are for design aid only: not guaranteed and not subject to production testing.
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MH88612K
Preliminary Information
Side View
0.020 Max (0.5 Max)
3.000 + 0.020 (76.2 + 0.5)
0.527+0.020 (13.4 + 0.5)
0.010 + 0.002 (0.25 + 0.05) 0.34 Max (8.5 Max) * 0.05 + 0.02 (1.3 + 0.5)
*
0.180 + 0.02 (4.6 + 0.5)
Notes: 1) Not to scale 2) Dimensions in inches). 3) (Dimensions in millimetres). *Dimensions to centre of pin & tolerance non accumulative.
0.15 + 0.02 (3.81 + 0.5)
0.100 + 0.010 (2.54 + 0.26)
Figure 4 - Mechanical Data
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