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MH88612B
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 Adjustable constant current feed. Relay driver Power Denial Wide Operating Range
DS5752 Issue 1 May 2002
Ordering Information MH88612BV-2 20 Pin SIL Package
0C to 70C
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 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 Control Systems
LPGND
VBAT PD VCC VEE AGND
Power Management
TF TIP RING RF
Current and Voltage Sensing
2-Wire to 4-Wire Conversion
VR VX
RV VRLY RC RD CD Over Current Protection Relay Drive Circuit Constant Current Feed Loop Supervision
VREF CAP
SHK
Figure 1 - Block Diagram
SEMICMF.019
1
MH88612B
TF LPGND VR VREF 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
Data Sheet
Figure 2 - Pin Connections
Pin Description
Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Name TF Description Tip Feed. Connects to external diode for protection
LPGND Loop Ground. Is the system ground reference with respect to VBAT. Normally connected to AGND. VR VREF VEE AGND PD VX TIP RING RF VCC RC RD RV VRLY CD VBAT CAP SHK Voice Receive (input) is the 4 wire analog signal to the device. Voltage Reference (Input) Constant current feed can be adjusted by the input voltage on VREF. This pin can also be grounded for normal 25mA loop current. Negative Power Supply Voltage (-5V). Analog Ground (0V). 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 device. Connects to the "Tip" lead of the telephone line. Connects to the "Ring" lead of the telephone line. Ring Feed (Input) is normally connected to Ring relay for negative battery feed voltage and ringing voltage input. Positive Power Supply Voltage (+5V). Relay Control (Input). Active high. Open collector sinks current when RC is at logic high. Ring Feed Voltage connects to pin 11 (RF) through a normally closed relay. Relay voltage Supply (+5V). Clamping Diode. Connects to AGND Negative Battery Feed Supply Voltage (-48V). Connects external capacitor to ground for ring trip. Switch Hook Detect (Output). Active high.
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SEMICMF.019
Data Sheet
Functional Description
MH88612B
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 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 (pin 4) is externally grounded, the constant current is set at 25mA. For a constant current setting between 18mA and 30mA, VREFcan be set between 8.75 Vdc and -6.35 Vdc. The relationship is defined by the equation:
ILOOP = VBAT - VREF mA (+2 mA) 1.89 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 VBAT 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.
Ringing And Ring Trip Detection
In Figure 3 a ringing signal (eg. 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 1.0F 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. 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 or system drive output of a codec. Applying AGND to the Ring Trip Filter Control pin as shown in Figure 4 will switch in the filter, whilst removing AGND, (with the switch in a tri-state condition), will switch out the filter. For applications using DTMF signalling, the capacitor can be permanently connected to ground.
SEMICMF.019
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MH88612B
Current Limit
Data Sheet
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 MH88612B 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 ILOOP is negligible and power consumption is minimized. The power denial function is useful for disabling a loop which may have a ground fault.
4
SEMICMF.019
Data Sheet
R1 K1 VBAT 11
MH88612B
RF MH88612B 3
~
+
90 VRMS 48V
D4
D3
1 15 2 9
TF RV LPGND
VR
D2
D1
VX
8
TIP
TIP
Protection Circuit
SHK
20
RING
10 13
RING PD RC
7
+5V C2 K1
16 VRLY 14 CAP RD R2 VEE 5 AGND 6 R4 19 C1 Q1
-
+
R3
RC
17 CD VBAT VCC 18 C3 -48V Components List R1 R2 R3, R4 C1 C2, C3 D1, D2, D3, D4 Q1 K1 200 10%, 1/4W 470k 5%, 1/4W 10k 5%, 1/4W 1.0f, 10%, 25V electrolytic capacitor 0.1f 20%, 50V ceramic de-coupling capacitors Diode rectifier 200V, 1A, IN4003 General Purpose switching transistor Relay E/M, 5V or 6V 1Form C +5V 12
(Pin 13)
-5V
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 - Application Circuit
SEMICMF.019
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MH88612B
Absolute Maximum Ratings*
Parameter 1 DC Supply Voltage LPGND = AGND Symbol VCC VEE VBAT VRLY VREF TS PD Min -0.3 -15 -80 -0.3 -60 -40 Max +15 +0.3 +0.3 +40 +15 100 2
Data Sheet
Units V V 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 VCC VEE VREF VBAT VRLY TS To Min 4.75 -5.25 -60 -40 0 Typ 5.0 -5.0 0 -48 5 100 Max 5.25 -4.75 -27 C 70 Units V V V V V 2 C Test Conditions
Adjustable
2 3
Storage Temperature
Storage Temperature
Typical figures are at 25C with nominal supply voltages and are for design aid only
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SEMICMF.019
Data Sheet
DC Electrical Characteristics - Voltages are with respect to GNDA unless otherwise stated.
Characteristics 1 Supply Current VCC VEE VBAT 2 3 4 5 Power Consumption Constant Current Line Feed Adjustable Loop Current Range Operating Loop Resistance ICC IEE IBAT PC ILoop ILoop RLoop 23 18 6.6 -3.8 150 2 160 1600 25 27 30 1200 mA mA A mA mW mW mA mA Sym Min Typ Max Units
MH88612B
Test Conditions
500
PD = Logic High PD = Logic Low, Idle Standby V BAT = -48V Active (Off Hook) VREF = AGND, V BAT = -48V Adjustable with Ext. VREF input, VBAT = -48V VBAT = -48V @ ILOOP = 18mA, RLOOP includes telephone set ILOOP = 25mA VBAT = 48V ILOOP = 30mA VBAT = 48V Active high logic
6 7
Ring Ground Over-Current protection Off-Hook Detect Output Low Voltage (On-hook) Output High Voltage (Off-hook) Off-Hook Detect Output Low Current (On-hook) Output High Current. (Off-hook) RC, PD Control Input Input Low Volt (no activation) Input High Volt (activation) RC, PD control Input Input Low Current (no activation) Input high current (activation) PD Control Input Input Low Current Input High Current VOL VOH IOL IOH VIL VIH IIL IIH IIL IIH
40 50 0.4 2.7 8 -200 0.7 2.0 50 0.5 0.5 0.3
mA mA V V mA A
8
9
Active high logic V V A mA mA mA LSTTL compatible
10
11
DC Electrical Characteristics are over recommended operating supply voltages. Typical figures are at 25C with nominal 5V supplies and are for design aid only.
SEMICMF.019
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MH88612B
AC Electrical Characteristics
Characteristics 1 2 3 4 5 6 7 Ringing Voltage (rms) 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 Longitudinal to Metallic Balance over 300-3400 Hz Total Harmonic Distortion at VX at Tip and Ring 13 14 15 Common Mode Rejection Ratio 2-wire to Vx Idle channel Noise Power supply rejection ratio VCC VEE VBAT CMRR Nc PSRR 26 26 26 40 THD RL Sym VRING REN 200
Zin
Data Sheet
Min 17
Typ
Max 90 25 3
Units Vrms Hz ms k
Test Conditions Superimposed on VBAT = -48V Cap = 1uF
600 100 -1.3 -0.15 -1.3 -0.15 20 30 -1.0 10 -1.0 -0.7 +0.15 -0.7 +0.15
dB
Input 3dBm, 1kHz across Tip and Ring 300-3400 Hz Input 1.0 Vrms 1kHz at VR ZLoad = 600 300 - 3400 Hz Input 0.5 Vrms , 1kHz across Tip and Ring, ZLoad = 600 Input 0.5 Vrms , 1kHz at V R ZLoad= 600 Input 0.5 Vrms Input 3dBm, 1 kHz across Tip and Ring, Input 1.0 Vrms 1kHz at VR Input 0.5Vrms, 1kHz C @ & VX Message 1 VPP ripple, 1kHz on VCC/VEE/VBAT,measure at VX and across Tip & Ring
dB dB dB
10 11 12
THL
20 50
30 55 0.1 1.0
dB dB %
0.1 50
1.0
% dB
14
dBrnC dB dB dB
Typical figures are at 25C with nominal 5V supplies and are for design aid only.
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SEMICMF.019
Data Sheet
0.08 Max 0.12 Max (2.03 Max)(3.05 Max) 2.120 Max (53.85 Max)
MH88612B
0.6 Max (15.24 Max)
1
0.180 + 0.020 (4.57 + 0.51) 0.020 + 0.005 (0.5 + 0.13) 0.010 + 0.002 (0.25 + 0.05) *0.05 + 0.02 * 0.100 + 0.010 (1.25 + 0.51) (2.54 + 0.25)
Notes: 1) Not to scale 2) Dimensions in inches. (Dimensions in millimetres) 3) Pin tolerances are non-accumulative. 4) Recommended soldering conditions: wave soldering max. temp: 260C for 10 secs. * Dimensions to centre of pin.
Figure 4 - Mechanical Data
SEMICMF.019
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