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MH88520-1
German Subscriber Line Interface Circuit (SLIC) Preliminary Information
Features
* * * * * * * * * * * Differential to single ended conversion Transformerless 2-2 wire conversion Minimum installation space Off-Hook detection and LED indicator drive Relay drive output Battery and ringing feed to line Logic interface: MUTE, SHK, RRC Mute of incoming audio Dial pulse detection Voltage surge protection German complex input impedance MH88520-1
ISSUE 4
April 1995
Ordering Information 20 Pin SIL Package 0C to 70C
Description
The Mitel MH88520-1 German Subscriber Line Interface Circuit provides a complete interface between the telephone line and a speech switch requiring only single bidirectional switch per crosspoint. The functions provided by the MH88520-1 include bidirectional differential to single ended conversion in the speech path, line battery feed, ringing feed and loop and dial pulse detection. The device is fabricated as a thick film hybrid in a 20-pin `single-in-line' (SIL) package allowing optimum circuit board packing density and very high reliability.
Applications
Line Interface for: * * * Intercoms Key Systems PABX
TIP (A) RING (B) RING FEED 1 RING FEED 2 Loop Feed/ Ring Feed JUNC Speech Circuit
MUTE VRLY SHK RRD RRC RGND Loop Detection Relay Drive Circuit LED THRESH ADJ
VBAT AGND
VDD
VEE
Figure 1 - Functional Block Diagram
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MH88520-1
Preliminary Information
TIP IC RING RF1 IC RF2 IC VEE LED SHK THRESH ADJ VDD AGND VBAT MUTE JUNC RRD RGND RRC VRLY
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 16 17 18 19 20 Name TIP IC RING RF1 IC RF2 IC VEE LED SHK THRESH ADJ VDD AGND VBAT MUTE JUNC RRD RGND RRC VRLY Description Tip Lead. Connects to the "Tip" lead (A-wire) of the telephone line. Internal Connection. Leave open circuit. Ring Lead. Connects to the "Ring" lead (B-wire) of the telephone line. Ring Feed 1. Connect to the Ring Relay contact. See Figure 5. Internal Connection. Leave open circuit. Ring Feed 2. Connect to normally closed contact of Ring Relay. See Figure 5. Internal Connection. Leave open circuit. Negative Power Supply Voltage. Normally -5V. LED Drive (Output). Drives an LED directly. A logic low indicates an off-hook condition. Switch Hook Detect (Output). A logic low indicates an off-hook and dial pulsing condition. Open collector output with 10k internal pull up to VDD. Allows adjustment of SHK detection threshold as shown in Figure 6. Positive Power Supply Voltage. Normally +5V. This provides current for both internal circuitry as well as the loop. Analog Ground. Supply and Battery Ground. Battery Supply Voltage. Normally -24V. This provides current to the loop. MUTE (Input). A logic low will mute signals coming from Tip-Ring to the JUNC pin. JUNCTOR. Ground (AGND) referenced transmit and receive speech path. Ring Relay Drive (Output). Connects to the ring relay coil. A logic low activates the relay. Relay Ground. Return path for relay supply voltage. Normally connected to AGND. Ring Relay Control (Input). A logic high activates the Ring Relay Drive (RRD) outputs. Relay Positive Supply voltage. Normally +5V. Connects to the relay coil and the relay supply voltage. An internal clamp diode from VRLY to GRND is provided.
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Preliminary Information
Functional Description The BORSH Functions
The MH88520-1 performs all of the Borsh functions of Battery Feed Overvoltage Protection, Ringing, Supervision and Hybrid (2-2 Wire).
MH88520-1
the SLIC, and converts the ground referenced input signal at JUNC of the SLIC into the non-balanced output signal at Tip-Ring of the telephone line.
Mute
A logic low at the MUTE input results in muted signals coming from Tip and Ring to the JUNC terminal while allowing signals from the JUNC terminal to Tip and Ring to be transmitted.
Return Loss at Tip-Ring
To maximise return loss, the impedance at Tip-Ring should match the SLIC's impedance (220R + 820R // 115nF). However, the SLIC's input impedance is dependent on the JUNCTOR termination resistance. Therefore the JUNCTOR must be terminated with 754. Figure 3 illustrates a typical connection between two SLICs through two crosspoint switches. Optimum return loss occurs when the JUNCTOR is terminated with 754. Since the JUNCTOR input/output impedances is 604 and the crosspoint switch resistances are 75 + 75, this configuration gives optimum return loss as shown in Figure 4.
Overvoltage Protection
The MH88520-1 is protected from short term (1ms) (+250V) between Tip and Ring, Tip and Ground, and Ring and Ground. However, additional protection circuitry may be needed depending upon the requirements which must be met for the final equipment.
Loop Detection
The loop detection circuit determines whether a low enough path is across Tip and Ring to be recognised as an off-hook condition. (Threshold impedance = 5.4k with no adjustment). This threshold level can be adjusted by the use of external resistors as shown in Figure 6. When an off-hook condition occurs the SHK and LED outputs toggle to a logic low level. These outputs also toggle during incoming dial pulses.
Hybrid
The 2-2 wire hybrid circuit converts the incoming balanced signal at Tip and Ring of the telephone line into a ground referenced output signal at JUNC of
1 TIP
MH88520-1
TIP JUNC 16
75
RING
3
RING
SLIC 1
CROSSPOINT SWITCH
1 TIP TIP
MH88520-1
16 JUNC
75
RING
8 RING
SLIC 2
CROSSPOINT SWITCH
Figure 3 - SLIC Crosspoint Switch Connection
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MH88520-1
Ringing
The relay drive circuit switches ringing onto Ring Feed (Fig. 7). The diode is present to suppress voltage transients during relay switching caused by the inductive coils of the relay. Ringing voltage included ac ringing (90VRMS typically) and DC line feed voltage (-24V typically).
Preliminary Information
Line Impedance
The MH88520-1's Tip-Ring (Zin) impedance is fixed at the German complex impedance. For correct SLIC impedance, JUNC must be appropriately terminated. See AC Electrical Characteristics.
Transmit and Receive Gain
Transmit Gain (JUNC to Tip-Ring) and Receive Gain (Tip-Ring to JUNC) are fixed (See AC Electrical Characteristics). For correct gain, the SLIC input impedance must match theline impedance and JUNC must be appropriately terminated.
Line Feed/Ring Feed Circuit
The line feed circuit provides loop current and the ability to apply ringing onto Tip and Ring. The impedance from Ring Feed to GND is 600 dc (although for ac it is optimised for a German complex impedance) which gives the loop current as: Voltage at Ring Feed pin Telephone Impedance + 600 Amps
Digital Applications
The 2-wire junctor output can be converted to a 4-wire circuit using the MH88524 (2-4 wire converter). This 4 wire circuit can be interfaced to a filter/codec to use in digital voice switched systems. Alternatively the MH88600/MH88612, digital ONS SLIC can be used.
The positive supply for the line feed circuit is VDD though the loop current is determined from Ring Feed and GND.
TYPICAL RETURN LOSS (dB)
10 20 30 40 50 60 550 600 650 700 750 800 850 900 950 LOAD IMPEDANCE ON JUNCTOR ()
Figure 4 - Return Loss VS Junctor Load Impedance
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Preliminary Information
Absolute Maximum Ratings
Parameter 1 Voltage Supplies Referenced to GND Symbol VDD VEE VBat 2 3 4 5 Clamp Diode Breakdown Voltage-VRef to RGND Operating Temperature Storage Temperature Power Dissipation VRLY TAMB TS PD 0 -55 Min -0.3 -15 -35
MH88520-1
Max +15 0.3 0.3 +32 +70 +125 4 Units V V V V C C
Watt
Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied.
AC Electrical Characteristics
Voltages are with respect to ground (VSS), TA = 25C, unless otherwise stated. Test conditions unless noted, VDD=5V, VEE=-5V, VBat=-24V).
Characteristics 1 2 Junctor to Differential Output (tip-ring) Gain Differential; Input (tip-ring) to Junctor Gain On/Off Hook Detection Threshold Loop Current Transhybrid Loss Passband Frequency Response Power Supply Rejection Ratio (@ Junctor) VBAT VDD VEE
Sym
Min
Typ -7.0 0.0
Max 0
Units dB dB
Test Conditions 1kHz, 0.5V source on pin 16. Note 2 1kHz, 0.5V Source Applied on pins 1&3 Note 1, 2 Note 1 Notes 1,2
3 4 5 6
IThresh
8.0
10 30 1.0
12
mA dB
dB
dB dB dB dB dB dB 3 105 dB V RMS z dBmp dBmp dB
Notes 1,2 200Hz - 3400Hz Notes 1,2. Ripple 0.1V 1kHz Notes 1,2 1kHz, 0.5V Notes 1
PSRR PSRR PSRR CMRR 46 ZOJ 18
30 40 40 40 50 604 30
7 8 9 10 11 12 13 14
Common Mode Rejection Ratio (Tip and Ring to Junctor) Longitudinal Balance Junctor Output Impedance Return Loss at Tip, Ring Max. Signal Level Max. Ringing Voltage Max. Ringing Frequency Idle Channel Noise at T-R at Junctor
1kHz Notes 1,2 Notes 1,2
25 NTR NJ -80 -80 30
60 -70 -75
Notes 1,2 Notes 1,2
15
Mute Attenuation
Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. Typical figures are at 25C with nominal+ 5V supplies and are for design aid only: not guaranteed and not subject to production testing. Note 1: 754 connected between JUNCTOR (pin 16) and 0V. Note 2: German Impedance connected between TIP (A) (pin 1) and RING (B) (pin 3).
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MH88520-1
DC Electrical Characteristics
Characteristics 1
S U P P L Y
Preliminary Information
.
Sym
VDD VEE VBat IDD
Min 4.5 -5.5 -30
Typ 5 -5 -24 8 6 1
Max 5.5 -4.5 -20
Units V V V mA mA mA V V
Test Conditions
Operating Supply Voltages
2
Operating Supply Currents
On Hook
IEE IBat High Level Input Voltage MUTE RRC
VIH
3
VIH
VIL
2.0 4.5 0.8 0.5 -28 700 100 10 1.5 100
4
5
I N P U T S
Low Level Input Voltage MUTE RRC High Level Input Current MUTE RRC Low Level Input Current MUTE RRC Sink Current LED RRD
VIL IIH IIH IIL IIL ILED IRRD
V V A A A A mA mA VRLY = RRC= 5V RGND = 0V VRRD < 1.5V RRC=RGND=0V VRLY = 5V VRRD > 4.5V LED Unconnected LED Unconnected
6
7
65
200
8
O U T P U T S
Relay to VDD Diode Clamp Current
IRLY
65
100
mA
9 10 11 12 13
High Level Output Voltage SHK Low Level Output Voltage SHK Low Level Output Current Power Consumption Max. Operating loop
VOH VOL IOL PC RL RL
4.5 0
5 .01 4
5.5 0.7
V V A mW
400 Loop at 18mA, 24V at 18mA, 30V
600 900

Typical figures are at 25C with nominal+ 5V supplies and are for design aid only: not guaranteed and not subject to production testing.
MH88520 Input Impedance
Variant 01 Country GERMANY Impedance 220 + 820 // 115nF
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Preliminary Information
MH88520-1
TIP RING
1 Optional Protection Circuit 3
MH88520-1
TIP 16 RING JUNC 15 MUTE AUDIO INPUT/OUTPUT MUTE CONTROL INPUT SWITCH HOOK OUTPUT OFF-HOOK LED DS1 RING CONTROL INPUT K1
Earth Ground
K1 4 10 RF1 SHK 9 19 17
R1 6 RINGING GENERATOR 90VRMS
LED
-24V
RF2
RRC RRD
14
VBAT VRLY 20 VEE AGND VDD RGND
8
13
12
18
Notes:
R1= 200, 1/4W, 5% K1= Relay E/M 5V, 1Form C C1, C2 = 0.1uF, 50V, Ceramic -5V C1 C2 +5V
Figure 5 - Typical Application Circuit
R and RTHRESH (k)
GND
R and RTHRESH (k)
VBAT
RG
RV
SLIC
11 THRESH ADJ
SLIC
11 THRESH ADJ
RG = 6000 x I VDD - (501 x I) R (k)
60 50 40 30 20 10 2 3
RV= (100 x VDD) - (6000 x I) (501 x I) - VDD R (k)
RG(k) (a) I = Threshold current
in Amps VDD = +5V
400
RV(k) (b)
200
4
5
6
7
8
10
15
20
25
Figure 6 - Off-Hook Threshold Adjust
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MH88520-1
VDD
Preliminary Information
TIP(a)
LINE FEED/ RING FEED
RING -24VDC +90VAC RING FEED 1 RING FEED 2 +5V VRLY RELAY COIL CLAMP DIODE
HYBRID
RRD
RELAY DRIVE CIRCUIT
RRC RGND
Figure 7 - Relay Drive Circuit
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Preliminary Information
MH88520-1
+7v +5V
+5V -24VDC 90VAC -24VDC
CONTROL LOGIC
A0 A1 A2
00 01 02 03 04 05 06 07
2 15 19 10 16
12
9 20 17 4 TIP 1 3
MH88520-1
RING 8 -8V 6 14 7
MD74SC137 1 OF 8 DECODER ADDRESS OUT A0 A1 A2 00 01 02 03 04 05 06 07
5 MORE SLICS
-24V 0V +5V +7V +5V
-24VDC 90VAC -24VDC
2 15 19 10 16 -8V +7V +5V 5 MORE SLICS 12 9 20 17 4 TIP 1 3 RING 7
MH88520-1
8 6 -24V +5V
14 0V
MD74SC137 1 OF 8 DECODER
-24VDC 90VAC -24VDC
2 15 19 10 12 9 20 17 4 TIP 1 3
A0-A2/D0-D3
J0
MT8812 J1 Crosspoint J 2 Switch
L0 J3 -L7
MH88520-1
RING 16 8 6 14 7
A0 A1 A2
CMOS 4512 8-INPUT MUX
SELECT OUTPUT
D0 D1 D2 | | D7
-8V
-24V
0V
Figure 8 - PABX Typical Application
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MH88520-1
Preliminary Information
Side View
0.080 Max (2.0 Max)
2.00+ 0.020 (50.8 + 0.5)
0.58+0.02 (14.7+0.5)
1234
19 20
0.010 + 0.002 (0.25 + 0.05)
0.12 Max (3.1 Max) * 0.05 + 0.01 (1.3 + 0.5) * 0.05 + 0.02 (1.3 + 0.05) 0.020 + 0.05 (0.51 + 0.13) *
Notes: 1) Not to scale 2) Dimensions in inches). 3) (Dimensions in millimetres). *Dimensions to centre of pin & tolerance non accumulative.
*
0.8 + 0.02 (4.6 + 0.5)
0.100 + 0.10 (2.54 + 0.13)
Figure 9 - Mechanical Data
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