MITEL MH88628

MH88628

Central Office SLIC
Preliminary Information
Features
•
ISSUE 5
April 1995
Ordering Information
Programmable gain, network balance and
impedance
MH88628
40 Pin SIL Package
•
Transformerless 2-4 wire conversion
•
Constant current with constant voltage fallback
for long loop capability
•
Pin compatible with MH88632, MH88620 and
MH88628
Applications
•
Unbalanced detection (Tip, Ring ground
sensing)
•
On/Off Premise PBX Line Cards
•
DID (Direct Inward Dial) Line Cards
•
Auto ring trip with zero crossing
•
Central Office Line Cards
•
On-Hook transmission (ANI) capability
•
Compatible with requirements of CCITT,
DOC/FCC and CSA/UL
Description
•
Excellent power dissipation (SIL vertical
mounting)
•
12/16kHz meter pulse injection control
•
Solid State TIP/RING reversals
•
Ringing amplifier
The Mitel MH88628 SLIC provides all of the
functions required to interface 2-wire off premise
subscriber loops to a serial TDM, PCM, switching
network of a modern PBX. The MH88628 is
manufactured using thick-film hybrid technology
which offers high voltage capability, reliability and
high density resulting in significant printed circuit
board area savings. A complete C.O. line card can
be implemented with very few external components.
VBat
RING
RF1
RF2
TIP
TF1
TF2
0°C to 70°C
LCA
LGND
Matched
Driver
Feed
Circuitry
and
Resistors
VDD
Loop
Current
Set
VEE
AGND
Switch-hook
Threshold Set
Ring
Filter
Switch-hook
Detect
Speech
Circuit
SHK
NS
UD
VRLY
RNGD
RD
2-4 Wire
Conversion
Unbalanced
Detection
External
Signal
Input
Decoder
Circuit
Ringing
Amplifier
SEL1 SEL2
ACRI DCRI
ESI
ESE
N1
N2
NATT
Impedance
Network
Gain Adjust
Z900 Z600 Z1
Z2
GRX1 GRX0 RX GTX1 GTX0 TX
Figure 1 - Functional Block Diagram
2-199
MH88628
Preliminary Information
TIP
RING
TF1
TF2
RF1
RF2
LGND
LCA
VBat
DCRI
RGND
VRLY
RD
SEL1
SEL2
ESI
ESE
AGND
NATT
N1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
N2
Z900
Z1
Z2
TX
RX
GTX0
GTX1
GRX0
GRX1
ACRI
Z600
NS
SHK
UD
IC
IC
IC
VEE
VDD
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Figure 2 - Pin Connections
Pin Description
Description
Pin #
Name
1
TIP
2
RING
3
TF1
Tip Feed 1. Access point for balanced ringing. Normally connects to TF2.
4
TF2
Tip Feed 2. Access point for balanced ringing. Normally connects to TF1.
5
RF1
Ring Feed 1. Access point for balanced ringing. Normally connects to RF2.
6
RF2
Ring Feed 2. Access point for balanced ringing. Normally connects to RF1.
7
LGND
8
LCA
Current Limit Set (Input). The current limit is set by connecting an external resistor to
ground. For 30mA default current, this pin is tied to GND.
9
VBat
Battery Voltage. Typically -48Vdc is applied to this pin.
10
DCRI
DC Ringing Voltage Input. A continuous 120Vdc is applied to this input.
11
RGND
Relay Driver Ground Connection.
12
VRLY
Relay Supply Voltage Connection.
13
RD
14
SEL1
Select 1 (Input). Refer to Table 5
15
SEL2
Select 2 (Input). Refer to Table 5.
16
ESI
External Signal Input. 12/16kHz meter pulse input.
17
ESE
External Signal Enable. Applies the external signal to the line.
18
AGND
Analog Ground. VDD and VEE return path.
19
NATT
Network Balance AT+T Node. Connects to N1 for a network balance impedance of AT&T
compromise (350Ω + 1kΩ // 210nF); the device’s input impedance must be set to 600Ω.
This node is active only when NS is at logic high. This node should be left open circuit when
not used.
2-200
Tip Lead. Connects to the “Tip” lead of subscriber line.
Ring Lead. Connects to the “Ring” lead of the subscriber line.
Battery Ground. VBat return path. Connected to system’s energy dumping ground.
Ring Drive (Output). Connects to ring relay coil.
MH88628
Preliminary Information
Pin Description (Continued)
Pin #
Name
Description
20
N1
Network Balance Node 1(Input). 0.1 times the impedance between pins N1 and N2 must
match the device’s input impedance, while 0.1 times the impedance between pins N1 and
AGND is the device’s network balance impedance. This node is active only when NS is at
logic high. This node may be terminated when not used (i.e., NS at logic low).
21
N2
Network Balance Node 2 (Output). See N1 for description.
22
Z900
23
Z1
Line Impedance Node 1 (Input). 0.1 times the times the impedance between pins Z1 and
Z2 is the device’s line impedance. This node must always be connected.
24
Z2
Line Impedance Node 2 (Output). 0.1 times the times the impedance between pins Z1
and Z2 is the device’s line impedance. This node should be left open circuit when not used.
25
TX
Transmit (Output). 4-Wire (AGND) referenced audio output.
26
RX
Receive (Input). 4-Wire (AGND) referenced audio input.
27
GTX0
Transmit Gain Node 0. Connects to GTX1 for 0dB transmit gain.
28
GTX1
Transmit Gain Node 1. A resistor to AGND provides transmit gain adjustment.
29
GRX0
Receive Gain Node 0. Connects to GRX1 for 0dB gain.
30
GRX1
Receive Gain Node 1. A resistor to AGND provides receive gain adjustment.
31
ACRI
AC Ringing Voltage Input. A 1.5Vrms 20Hz signal is applied to this input.
32
Z600
Line Impedance 600Ω Node (Output). Connects to Z1 for a line impedance of 600Ω.
This pin should be left open circuit when not used.
33
NS
Network Balance Setting (Input). The logic level at NS selects the network balance
impedance. A logic 0 enables an internal balance equivalent to the input impedance (Zin).
While a logic 1 enables an external balance 0.1 times the impedance between pins N1 and
AGND balanced to 0.1 times the impedance between pins N1 and N2. The impedance
between N1 and N2 must be equivalent to 10 times the input impedance (Zin).
34
SHK
Off-Hook Indication (Output). A logic low output indicates when the subscriber equipment
has gone Off-Hook.
35
UD
Unbalance Detect (Output). A log IC low output indicates when the DC current flow in the
Tip and Ring leads is unbalanced, indicating that the subscriber equipment has grounded
the Ring lead.
36,37,38
IC
Internal Connection. These pins are internally connected and must be left open
39
VEE
Negative Supply Voltage. -5V dc.
40
VDD
Positive Supply Voltage. +5V dc.
Line Impedance 900Ω Node. Connects to Z1 for a line impedance of 900Ω. This node
should be left open circuit when not used.
2-201
MH88628
Preliminary Information
Absolute Maximum Ratings*
Parameter
1
Supply Voltage
2
Storage Temperature
Sym
Min
Max
Units
Comments
VBat
VDD
VEE
VDCRI
+0.3
-0.3
+0.3
-0.3
65
6
-6
140
V
V
V
V
With respect LGND
TS
-40
+125
°C
* Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied.
Recommended Operating Conditions
Parameter
Sym
Min
Typ*
Max
Units
1
Supply Voltage
VBat
VDD
VEE
-44
4.75
-4.75
-48
+5.0
-5.0
-60
5.25
-5.25
V
V
V
2
Operating Temperature
TOP
0
20
70
°C
3
AC Ring Generator
33
Vrms
Hz
130
Vdc
Typ*
Max
Voltage
Frequency
4
90
17
Comments
DCRI
Input DC Voltage
VDCRI
110
120
* Typical figures are at 25° C with nominal + 5V supplies for design aid only.
DC Electrical Characteristics‡
Characteristics
Sym
Operating Loop Current
Var in loop current from nominal
ILoop
ILoop
ILoop
ILoop
Operating Currents
Min
Test Conditions
30
±2
mA
mA
mA
mA
RLoop=0Ω
2300Ω VBat =-48V
RLoop=0Ω, LCA GND
IBat
32
mA
IBat
2
mA
IDD
IEE
25
25
mA
mA
RLoop =0 (off Hook),
LCA=GND
RLoop = open (OnHook)
On-hook or Off-Hook
On-Hook or Off-Hook
Power Dissipation
PDO
PD1
2
300
W
mW
Active
Standby/Idle
SHK
UD
Low level Output Voltage
High Level Output Voltage
VOL
VOH
0.5
3.7
V
V
IOL = 400µA
IOH= 40µA
SEL1
SEL2
ESE
NS
Low Level Input Voltage
High Level Input Voltage
VIL
VIH
0.8
2.4
V
V
High Level Input Current
Low Level Input Current
IIH
IIL
20
20
µA
µA
1
2
3
45
Units
16
4
5
6
‡ DC Electrical Characteristics are over recommended operating conditions unless otherwise stated.
* Typical figures are at 25°C with nominal +5V supplies and are for design aid only.
2-202
VIH=5.0V
VIL=0.0V
MH88628
Preliminary Information
AC Electrical Characteristics‡
Characteristics
Sym
Min
Typ*
Max
Units
Test Conditions
1
TX Gain
0
dB
externally adjustable
2
RX Gain
0
dB
externally adjustable
3
Ringing Capability
5
REN
4
On-Hook Transmission
Signal Input Level
Gain
6
5
External Signal Output Level
6
SHK Rise Time
Fall time
7
2-Wire Termination
Impedance
Off-Hook Detect Threshold
9
2-Wire Return Loss
10
Longitudinal Balance
Longitundinal to Metallic
11
Longitudinal Current
Capability
12
Idle channel Noise
Rx to T-R
T-R to Tx
13
Transhybrid Loss
14
Unbalanced Detect Threshold
15
Analog Signal Overload Level
At Tip and Ring
Vrms
dB
VBat=-48V
T-R load = 10kΩ min.
2.25
Vrms
VBat= -48V, T-R load=
200Ω LCA=0V, Zo-600Ω,
Gain=0dB
1
1
ms
ms
Dial Pulse Detection
600/
900
Ω
10
mA
1.75
tR
tF
8
2.0
Selectable
20
20
20
dB
dB
dB
300 to 500Hz
500 to 2500Hz
2500 to 3400Hz
58
53
dB
dB
200-1000Hz
1kHz - 3k4Hz
mA
20mA per lead
40
NCR
NCX
THL
22
IUB
8
12
dBrnC
dBrnC
40
dB
10
mA
4
T-R=600Ω, VBat=-48V
16
Ringing Signal Voltage
17
Ringing Frequency
18
Ring Trip Delay
100
ms
19
Absolute Gain, Variation
+0.1
dB
0dB at T-R, 1kHz
20
Relative Gain, reference to
1kHz
+0.05
dB
300-3400Hz
dB
1kHz, 100mVpp
21
90
dBm
200-3400Hz
17
Vrms
33
Power Supply Rejection Ratio PSRR
VBat
24
VDD
24
VEE
24
* Typical figure are at 25°C with nominal +5V supplies and are for design aid only.
Hz
‡ AC Electrical Characteristics are over recommended operating conditions unless otherwise stated.
Notes:
Impedance set by external network of 600Ω or 900Ω default.
External network for test purposes consists of 2200Ω + 8200Ω // 11.5nF between pins Z1 and Z2, the equivalent Zin has 1/10th the impedance
and is equivalent o 220Ω+820Ω // 115nF.
Test condition uses a Zin value of 600Ω, 900Ω and the above external network.
Test conditions use a transmit and receive gain set to 0dB default and a Zin value of 600Ω unless otherwise stated.
“Ref” indicates reference impedance which is equivalent to the termination impedance.
“Net” indicates network balance impedance.
Refer to Table 1, 2 for TX, RX gain adjustment.
2-203
MH88628
Preliminary Information
Functional Description
Loop Current Setting
The SLIC uses a transformerless electronic 2-wire to
4-wire conversion which can be connected to a
Codec to interface the 2 wire subscriber loops to a
time division multiplexed (TDM) pulse code
modulated (PCM) digital switching network. For
analog applications, the Tx and Rx of the 2-4 wire
converter can be connected directly to an analog
crosspoint switch such as the MT8816. Powering of
the line is provided through precision battery feed
resistors. The MH88628 also contains control,
signalling and status circuitry which combines to
provide a complete functional solution which
simplifies the manufacture of line cards. This
circuitry is illustrated in the functional block diagram
in Fig. 1. The MH88628 is designed to be pin
compatible with Mitel’s MH88632 and MH88625.
This allows a common PCB design with common
gain, input impedance and network balance.
The MH88628 SLIC is a constant current with
constant voltage fallback design. This design feature
provides for long loop capability regardless of the
constant current setting. Refer to Graph 1.
Approvals
FCC part 68, CCITT, DOC CS-03, UL 1459, CAN/
CSA 22.2 No.225-M90 and ANSI/EIA/TIA-464-A are
system level safety standards and performance
requirements. As a component of a system, the
MH88628 is designed to comply with the applicable
requirements of these specifications.
The LCA (Loop Current Adjust) pin is an input to an
internal resistor divider network which generates a
bias voltage. The loop current is proportional to this
voltage. The loop current can be set between 20 and
45mA by various connections to the LCA pin as
illustrated in Table 5 and Figure 8. The loop current
during a fault condition will be limited to a safe level.
Primary over-current protection is inherent in the
current limiting feature of the 200Ω battery feed
resistors. Refer to Graph 1.
Receive and Transmit Audio Path
The audio signal of the 2-wire side is sensed
differentially across the external 200Ω feed resistors
and is passed on to a second differential amplifier
stage in the 2W/4W conversion block. This block
sets the transmit gain on the 4-wire side and cancels
signals originating from the receive input before
outputting the signal.
Programmable Transmit and Receive
Gain
Battery Feed
The loop current for the subscriber equipment is
sourced through a pair of matched 200Ω resistors
connected to the Tip and Ring. The two wire loop is
biased such that the Ring lead is 2V above VBat
(typically -46V) and the Tip lead is 2V below LPGD
(typically -2V) during constant voltage, constant
current mode.
The SLIC is designed for a nominal battery voltage
of -48Vdc and can provide the maximum loop current
of 45mA under the condition.
The MH88628 is designed to operate down to a
minimum of 16mA dc, with a battery voltage of -44V.
The Tip and Ring output drivers can operate within
2V of VBat and LGND rails. This permits a maximum
loop range of 2300Ω.
2-204
Transmit Gain (Tip-Ring to Tx) and Receive Gain (Rx
to Tip-Ring) are programmed by connecting external
resistors (RRX and RRT) from GRXI to AGND and
from GTX1 to AGND as indicated in Figure 3 and
Tables 1 and 2. The programmable gain range is
from -12dB to +6dB; this wide range will
accommodate any loss plan. Alternatively, the
default Receive Gain of 0dB and Transmit Gain of
0dB can be obtained by connecting GRX0 to GRX1
and GTX0 to GTX1. In addition, a Receive gain of
+6dB and Transmit Gain of +6dB can be obtained by
not connecting resistors RRX and RTX. For correct
gain programming, the MH88628’s Tip-Ring
impedance (Zin) must match the line termination
impedance.
For optimum performance, resistor RRX should be
physically located as close as possible to the GRX1
input pin, and resistor RTX should be physically
located as close as possible to the GTX1 input pin.
MH88628
Preliminary Information
70
60
Constant
Voltage
Region
50
40
ILoop
(mA)
Constant
Current Region
30
20
10
0
1kΩ
2kΩ
RLoop (Ω)
Graph 1 - ILoop/RLoop Characteristics
Two wire Port Termination Impedance
The AC termination impedance of 600 or 900Ω, of
the 2W port, is set using active feedback paths to
give the desired relationship between the line
voltage and the line current. The loop current is
sensed differentially across the two feed resistors
and converted to a single ended signal. This signal is
fed back to the Tip/Ring driver circuitry such that
impedance in the feedback path gets reflected to the
two wire port. The MH88628’s Tip-Ring impedance
(Zin) can be set to 600Ω, 900Ω or to a user
selectable value. Thus, Zin can be set to any
international requirement. The connection to Z1
determines the input impedance. With Z1 connected
to Z600, the line impedance is set to 600Ω. With Z1
connected to Z900, the line impedance is set to
900Ω. A user defined impedance can be selected
which is 0.1 times the impedance between Z1 and
Z2.
For example, with 2200Ω in series with 11.5nF in
parallel with 8200Ω, all between Z1 and Z2, the
devices line impedance will be 220Ω in series with
115nF in parallel with 820Ω. See Table 3 and Figures
4 & 5.
Network Balance
Transhybrid loss is maximized when the line
termination impedance and SLIC network balance
are matched. The MH88628’s network balance
impedance set can be set to Zin, AT&T (350Ω + 1kΩ
//210nF) or to a user selectable value. Thus, the
network balance impedance can be set to any
international requirement, A logic level control input
NS selects the balance mode. With NS at logic low,
an internal network balance impedance is matched
to the line impedance (Zin). With NS at logic high, a
user defined network balance impedance is selected
which is 0.1 times the impedance between N1 and
AGND. For example, with 2200Ω in series with
11.5nF in parallel with 8200Ω, all between N1 and
AGND, and NS at logic high, the devices network
balance impedance is 220Ω in series with 115nF in
parallel with 820Ω; the impedance between N1 and
N2 must be equivalent to 10 times the input
impedance (Zin). In addition, with NS at logic high, an
AT&T network balance impedance can be selected
by connecting NATT to N1; in this case, no additional
network is required between N1 and N2. See Table 4
and Figure 6.
12/16kHz Meter Pulse
The MH88628 provides control of an external signal
path to the driver. A 12/16kHz continuous signal can
be applied to the ESI pin. Control of the ESE input
allows the metering signal to be transmitted to the
line.
Unbalanced Detection
The Unbalanced Detect (UD) pin goes low when the
DC current through the two battery feed resistors is
unbalanced i.e., when the average DC current into
the Ring lead exceeds the current flow out of the Tip
lead (indicating that the Ring lead has been
grounded).
When the SLIC is interfaced to ground start
subscriber equipment during the idle state, the UD
output is monitored for indication of the subscribers
Ring Ground signal. The maximum loop current
supplied by the feed circuitry under this condition is
limited.
2-205
MH88628
Preliminary Information
Longitudinal Balance
Ring Trip Detection
The longitudinal balance specifies the degree of
common mode rejection in the 2 to 4 wire direction.
Precision laser trimming of internal resistors in the
hybrid ensures good overall longitudinal balance.
The interface circuitry can operate in the presence of
induced longitudinal currents of up to 40mA at 60Hz.
The interface permits detection of an Off-Hook
condition during the ringing. If the subscriber set
goes Off-Hook when the ringing signal has been
applied, the DC loop current flow will be detected
within approx. 100msecs and the SHK output will go
low. The ring relay is automatically disabled by the
internal hardware.
Off-Hook and Dial Pulse Detection
Control Decode
The SHK pin goes low when the DC-loop current
exceeds a specified level. The threshold level is
internally set by the bias voltage of the switch-hook
detect circuitry. Dial pulse can be detected by
monitoring the interruption rate at the SHK pin.
These dial pulses would be debounced by the
system’s software.
The different modes of operation are selected by
decoding the SEL1 and SEL2 inputs (see Table 5).
DTMF
The DTMF tones are transmitted and received at the
4-wire port.
MH88628
Z
Transmit Gain:
-
Z
(Tip-Ring to Tx)
TX 25
+
10kΩ
AV= -20log
10kΩ
GTX1
28
GTX0
27
RTX
RTX =
5kΩ ]
[ 0.5 + RTX
5kΩ
10(-AV/20)-0.5
Example
RTX=38kΩ; AV= +4dBV
Z
+
RX
10kΩ
10kΩ
26
GRX1
30
GRX0
29
RRX
Receive Gain:
(RX to Tip-Ring)
AV= -20log
RRX =
5kΩ ]
[ 0.5 + RRX
5kΩ
10 (-AV/20)
-0.5
Example:
RRX=4.6kΩ; AV= -4dBV
Figure 3 - Gain Programming with External Components
2-206
MH88628
Preliminary Information
24
Z2
MH88628
Z2
NC
MH88628
23
Z1
Z1
24
NC
23
22
22
Z900
Z900
NC
32
NC
Z600
32
Z600
Input impedance (Zin) set to 600Ω
Input Impedance (Zin) set to 900Ω
Note: Make connection between Z1 and other points as short as possible
Figure 4 - Input Impedance (Zin) Settings with Zin equal to 600 or 900Ω
Z2
10 x Z
in
24
RP
10 x Zin
MH88628
Z1
Z2
CP
23
22
Z1
RS
Z900
Z600
32
Zin = 0.1 x
[ RS +
1
1/RP + (S x CP)
]
where S = j x w
and w = 2 x Π x f
Example:
Notes:
1) The 10xZin network must be set to 10 x the desired input impedance (Zin).
2) The network balance must be set to the desired network balance. See
section on network balance.
3) Make connection between Z1 and component as short as possible.
If RS = 2200Ω, RP = 8200Ω, CP= 11.5nf
Then the input impedance (Zin) is 220Ω in
series with 820Ω in parallel with 115nF.
Figure 5 - Input Impedance (Zin) Settings with Zin not equal to 600 to 900Ω
2-207
MH88628
Preliminary Information
N2
MH88628
N1
NATT
NS
21
21
N2
MH88628
20
20
N1
19
NATT
33
NS
19
33
VDD
Network balance is set to the input
Impedance (Zin)
Network balance is set to the AT&T compromise
network (350Ω + 1000Ω // 210nF)
impedance. The input impedance must be
set to 600W.
Note: Make connection between Z1 and other points as short as possible
Figure 6 - Network Balance Setting with NETBAL equal to Z in or AT&T
10 x Zin
N2
MH88628
N1
21
RP
10 x Zin
N2
10 x
NETBAL
N1
20
19
CP
RS
NATT
1
ZNETBAL = 0.1 x
33
NS
[ RS + 1/RP + (S x CP) ]
VDD
where S = j x w
and w = 2 x Π x f
Example:
Notes:
1) The 10xZin network must be set to 10 x the desired input impedance (Zin).
2) The network balance must be set to the desired network balance. See
section on network balance.
3) Make connection between Z1 and component as short as possible.
If RS = 2200Ω, RP = 8200Ω, CP= 11.5nf
Then the network balance impedance
(ZNETBAL) is 220Ω in series with 820Ω
in parallel with 115nF.
Figure 7 - Network Balance Setting with NETBAL not equal to Zin or AT&T
2-208
MH88628
Preliminary Information
Tables 1 & 2: Transmit and Receive Gain Programming
Transmit
Gain (dB)
RTX Resistor
Value (Ω)
+6.0
No Resistor
+4.0
38.3k
Results in 0dB overall gain when used with Mitel A-law codec (i.e.
MT8965)
+3.7
32.4k
Results in 0dB overall gain when used with Mitel µ-law codec (i.e.
MT8964)
0.0
GTX0 to GTX1
-3.0
5.49k
Notes
-6.0
3.32k
-12.0
1.43k
Receive Gain
(dB)
RRX Resistor
Value (Ω)
+6.0
No Resistor
0.0
GRX0 to GRX1
-3.0
5.49k
-3.7
4.87k
Results in 0dB overall gain when used with Mitel A-law codec (i.e.
MT8965)
-4.0
4.64k
Results in 0dB overall gain when used with Mitel µ-law codec (i.e.
MT8964)
-6.0
3.32k
-12.0
1.43k
Notes
Note 1: See Figures 3 and 4 for additional details.
Note 2: Overall gain refers to the receive path of PCM to 2-wire, and transmit path of 2-wire to PCM.
Table 3: Input Impedance Settings
Z900
Resulting input impedance (Zin)
NA
600Ω
NA
Connect Z1
to Z900‘
900Ω
NA
NA
0.1 x impedance between Z1 & Z2
Z2
Z1
NA
Connect Z1 to Z600
NA
Connect Z1
to Z9000
Connect network from Z1 to Z2
Z600
Note 1: NA indicates high impedance (10kΩ) connection to this pin does not effect the resulting network balance.
Note 2: See Figure 4 & 5 for Application Circuits.
Table 4: Network Balance Settings
NS (Input)
N2
N1
NATT
Resulting input impedance (Zin)
Low
NA
NA
NA
Equivalent to Zin
High
NA
High
Connect N1
to NATT
Connect network from N1 to
AGND equivalent to 10 x
NETBAL. Connect network
from N1 to N2 equivalent to 10
x Zin.
AT&T compromise (350Ω + 1kΩ // 210nF)
Zin must be 600Ω
NA
0.1 x impedance between N1 & N2
Note 1: NA indicates high impedance (10kΩ) connection to this pin does not effect the resulting network balance.
Note 2: Low indicates Logic Low.
Note 3: See Figures 6 and 7 for Application Circuit.
2-209
MH88628
Preliminary Information
+5V
R
LCA
LCA
LCA
R
-5V
8a
8c
8b
Loop Current Setting
Figure 8 - Loop Current Setting
High Voltage capability
Loop Length
Inherent in the thick-film process is the ability of the
substrate to handle high voltage. The standard Mitel
thick-film process provides dielectric strengths of
greater than 1000VAC or 1500VDC. The thick-film
process allows easy integration of surface mount
components such as the high voltage bi-polar power
transistor line drivers. This allows for simplier, less
elaborate and less expensive protection circuitry
required to handle high voltage transients and fault
conditions caused by lightning, induced voltages and
power line crossings.
The MH88628 can accommodate loop length of up to
2300Ω
minimum
(including
the
subscriber
equipment). This corresponds to approximately 8km
using 26AWG twisted pair or 15km using 24AWG
twisted pair.
On-hook Transmission
The MH88628 provides for on-hook transmission
which supports features such as Automatic Numbers
Identification (ANI). The (ANI) information is a FSK
signal originating from and sent by the C.O. during
the off period of the ringing voltage being sent to the
subscribers set. The signal is present during the off
period between the first and second ring. The
subscribers set decodes the FSK signal and displays
the calling party’s number.
TIP Disable
A relay driver, controlled by SEL1 and SEL2, is
provided to drive a relay which can be used to
disable the TIP line when the MH88628 is used for a
ground start central office interface.
2-210
Central Office Operation
The MH88628 can be configured for ground start
C.O. applications with the addition of Q1, D1 and K2,
as shown in Figure 9. Ground start requires control of
the Tip lead to remove battery ground from
subscriber loop. For loop start applications, control of
the Tip lead is not required.
C.O’s perform Tip/Ring reversals to indicate that a
tool call has been dialled. The Tip/ring reversal can
indicate a toll diversion signal.
Internal Ringing Amplifier Operation
The MH88628 offers an on-board ringing amplifier. A
1.5 VRMS, 20Hz signal is amplified internally and
applied to TIP and RING leads in a balanced
configuration. A +120Vdc supply are applied
continuously to the MH88628. The decode signals on
SEL1 and SEL2 enable the ringing signal to the TIP
and RING when required.
MH88628
Preliminary Information
-VBat
SYSTEM
+5V
GROUND
VBat
VDD
VEE
MH88628
-5V
RX
VR
GRX0
VX
CODEC
GRX1
LCA
AGND
TX
GTX0
TF1
GTX1
TF2
SHK
P
R
O
T
E
C
T
I
LINE
CONTROLLER
TIP
UD
LOGIC
Z1
Z600
SEL1
SEL2
RING
O
N
ESE
12/16kHz
RF1
ESI
Metering Source
K1B
ACRI
+5V
K1
RF2
1.5VRMS 20Hz
Source
DCRI
VRLY
+
RD
120VDC
Supply
RGND
NS
Figure 9 - OPS SLIC Configuration Applications Circuit - Normal Ringing
Graph 2 - Loop Current Setting
65mA
(Ω/10)
ILoop/mA
50
To -5V
O/C LCA
40
35.3mA
30
LCA
= 0V
28.48m
20
To +5V
10K
100K
(Ω/10 + 10mA)
1M
R(LCA) Ω
2-211
MH88628
Preliminary Information
Table 5: Control Decode Table
Mode
Condition
SEL1
SEL:2
1
Normal Operation
0
0
2
Apply internal balanced ringing
1
0
3
Reverse TIP and RING
0
1
4
Enable Relay Driver
1
1
Table 6: Loop Current Setting
Loop
Current
Ref. Fig #
20
8a
Connect 10kΩ from LCA to +5V
25
8a
Connect 22kΩ from LCA to +5V
30
8a
Connect 36kΩ from LCA to +5V
35
8c
LCA open circuit
40
8b
Connect 24kΩ to -5V
45
8b
Connect 10kΩ from LCA to -5V
LCA Pin Connection
PRIMARY MDF
PROTECTION
T
SECONDARY PROTECTION
HEAT COIL
T
F1
R1
MH88628
PRO1
GAS TUBE
F2
R2
R
R
HEAT COIL
SUGGESTED COMPONENTS:
F1, F2 1A, 250VAC, SLO-BLOW LITTLEFUSE 230 2AG
R1, R2, 10Ω, 1000V, 1/2W RESISTOR (FLAME RATED)
PRO1 SOLID STATE TRANSIENT SUPPRESSOR, EG TISP2300L, P2703AB
F1, R1 AND F2, R2 MAY BE FUSIBLE RESISTORS OR PTCs
Figure 10 - Typical Protection Circuit
2-212
MH88628
Preliminary Information
0.080 Max
(2.0 Max)
Side View
4.20 + 0.020
(50.8 + 0.5)
0.80+0.03
(20.3+0.76)
1 2 3 4
39 40
0.010 + 0.002
(0.25 + 0.05)
0.12 Max
(3.1 Max)
1
2
3
0.05 + 0.01
(1.3 + 0.5)
Notes:
1) Not to scale
2) Dimensions in inches).
3) (Dimensions in millimetres).
*Dimensions to centre of pin &
tolerance non accumulative.
*
0.25 + 0.02
(6.35 + 0.05)
*
0.020 + 0.05
(0.51 + 0.13)
*
0.175 + 0.02
(4.445 + 0.5)
0.100 + 0.10
(2.54 + 0.13)
Figure 11 - Mechanical Data
2-213
MH88628
Notes:
2-214
Preliminary Information