™
Le9502
Ringing Subscriber Line Interface Circuit
VE950 Series
APPLICATIONS
!
Short/Medium Loop: approximately 2000 ft. of 26 AWG,
!
!
!
!
and 5 REN loads
Voice over IP/DSL – Integrated Access Devices, Smart
Residential Gateways, Home Gateway/Router
Cable Telephony – NIU, Set-Top Box, Home Side Box,
Cable Modem, Cable PC
Fiber–Fiber In The Loop (FITL), Fiber to the Home
(FTTH)
Wireless Local Loop, Intelligent PBX, ISDN NT1/TA
DESCRIPTION
Legerity’s Le9502 Ringing Subscriber Line Interface Circuit
(RSLIC) device from the VE950 series has enhanced and
optimized features to directly address the requirements of
Voice over Broadband applications. Its goal is to reduce system
level costs, space, and power through higher levels of
integration, and to reduce the total cost of ownership by offering
better quality of service. The Le9502 RSLIC device provides a
totally configurable solution to the BORSCHT functions for two
lines. The resulting system is less complex, smaller, and
denser, yet cost effective with minimal external components.
The Le9502 RSLIC device requires only two power supplies:
+3.3 VDC and nominally +12 VDC. The latter power supply can
range from +8 VDC to +40 VDC, depending on the application.
A single TTL-level clock source drives an external transistor
which controls the ramp voltage that in turn feeds the switching
regulators. Five programmable states are available: Active,
Reverse Polarity, Ringing, Standby, and Disconnect. The DC
feed, two-wire AC input impedance, hook-switch threshold, and
ring trip threshold are programmable via external discrete
components. Binary fault detection is provided upon
application of fault conditions or thermal overload.
FEATURES
!
Integrated Dual-Channel Chip set
— Built-in boost switching power supply tracks line voltage
minimizing power dissipation
— Only +3.3 V and +12 V (nominal) required
— Wide range of input voltages (+8 V to +40 V) supported
— Minimal external discrete components
— 44-pin eTQFP package
!
Ringing
—
—
—
—
—
70 Vpk into 5REN
90 Vpk capable
Sinusoidal or trapezoidal capability
DC offset support
Common differential interface for both channels
!
World Wide programmability:
— Two-wire AC impedance
— Dual Current Limit
— Loop closure and ring trip thresholds
BLOCK DIAGRAM
Le9502
!
Five SLIC States, including:
— Low power Standby state
— Reverse Polarity
RELATED LITERATURE
!
!
!
!
!
!
081189 Le9500 RSLIC Device Data Sheet
081208 Le9501 RSLIC Device Data Sheet
080696 Le77D11 VoSLIC™ Device Data Sheet
080697 Le78D11 VoSLAC™ Device Sheet
080716 Le77D11 /Le78D11 Chip Set User’s Guide
080780 Layout Considerations for the Le77D11 and
Le9502 Devices Application Note
Differential
Switching Power
Supply
2-wire
Tip+Ring
Interface
Ring
Tip
2-wire to 4-wire
conversion
Codec
Device
Codec
Interface
2-wire to 4-wire
conversion
ORDERING INFORMATION
Device
Le9502TC
Package
44-pin eTQFP
Switching Power
Supply
2-wire
Tip+Ring
Interface
Ring
Tip
Document ID#
081007
Date:
Rev:
C
Version:
Distribution:
Public Document
Apr 21, 2004
1
TABLE OF CONTENTS
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Related Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Product Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Block Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Two-Wire Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Switcher Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Signal Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Fault Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Signal Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Reference Current Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Control Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Connection Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Operating Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Supply Currents and Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Device Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Test Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Application Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Line Card Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Physical Dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
44-Pin eTQFP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Revision A1 to B1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Revision B1 to C1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
2
Le9502 VE950 Series Data Sheet
PRODUCT DESCRIPTION
The VE950 series Le9502 RSLIC device uses reliable, dielectrically isolated, fully complementary bipolar technology to
implement BORSCHT functions for short loop applications. Internal power dissipation is minimized by two independent line
voltage tracking, buck-boost switching regulators. Two power supplies are required: 3.3 V and a positive supply (V
SW
). A TTL-
level clock is required to drive the switching regulator. Five programmable states control loop signaling, transmission, and ringing.
The Le9502 RSLIC device DC current feed limit (I
SC
) is resistor-programmable up to 45 mA.
Figure 1. Typical Le9502 RSLIC/Codec Application in an 8-Port Integrated Access Device in Customer Premises
Din
1
Dual
RSLIC
Codec
Dout
Dual
RSLIC
Dual
RSLIC
Dual
RSLIC
Codec
PCM I/F
DCLK/CS
Codec
Din
Codec
Dout
Data Interfaces
8
DSP
+
Network
Processor
Loop/Cable
MODEM
WLL
DSLAM/
HEADEND
Ethernet USB HomePNA
BLOCK DESCRIPTIONS
Figure 2.
Le9502 RSLIC Device Block Diagram
F
1
Fault
Detection
Signal
Transmission
VRINGM
VRINGP
VINP
1
VINM
1
VOUT
1
VHP
1
CFILT
1
LPF
1
DET
1
RTRIP
1
RDC
A
1
(TIP)
Two-Wire
Interface
B
1
(RING)
VREG
1
SD
1
ILS
1
CHS
1
VSW
VRAMP
Signal
Conditioning
Switcher
Controller
Ref
Current
Generator
Switcher
Controller
Control
Logic
C1
1
C2
1
ISET
SD
2
ILS
2
CHS
2
VREG
2
A
2
(TIP)
Control
Logic
C1
2
C2
2
B
2
(RING)
Two-Wire
Interface
Signal
Conditioning
DET
2
RTRIP
2
Signal
Transmission
Fault
Detection
VINP
2
VINM
2
VOUT
2
VHP
2
CFILT
2
LPF
2
F
2
BGND
1
BGND
2
AGND
VCC
Le9502 VE950 Series Data Sheet
3
Two-Wire Interface
The two-wire interface block provides DC current and sends/receives voice signals to a telephone connected via the A
i
(Tip) and
B
i
(Ring) pins. The A
i
(Tip) and B
i
(Ring) pins are also used to send the ringing signal to the telephone. The Le9502 RSLIC device
can also be programmed in Disconnect state to place the A
i
and B
i
pins at high impedance with the Switching Regulator disabled.
DC Feed
DC feed is controlled in the Le9502 RSLIC device. Only the current limit threshold (I
LTH
) can be set via the RDC pin. The current
limit threshold can be set from 0 to 30 mA.
Referring to
Figure 3,
the DC feed curve consists of two distinct regions. The first region is a flat anti-sat region that supplies a
constant Tip-Ring voltage (V
AB
open). The second region is a constant current region that begins when the loop current reaches
the programmed current limit threshold (I
LTH
). This region looks like a constant current source with 3.2 kΩ shunt resistor. The
short circuit current is nominally 17.0 mA greater than I
LTH
.
A block diagram of the DC feed control circuit is shown in
Figure 4.
In the anti-sat region, current source CS1 creates a constant
reference current, which is limited to sub-voice frequencies by C
LPFi
. This filtered current is then steered by the Polarity Control,
depending on whether the SLIC mode is Standby, Normal Active, or Reverse Polarity. The steered current then takes one of two
paths to the Level Shift block, where it is used to set V
A
(TIP) and V
B
(RING). This voltage from the Level Shift block is buffered
by the output amplifiers and appears at A
i
(TIP) and B
i
(RING).
When I
LOOP
/500 becomes greater than I
LTH
/500, the difference is subtracted from CS1, and again filtered by C
LPFi
. This reduced
current causes a reduced DC feed voltage. In Standby and Normal Active, A
i
(TIP) is held constant, while B
i
(RING) is changed
to reduce the feed voltage. In Reverse Polarity, A
i
(TIP) and B
i
(RING) are swapped. When (I
LOOP
-I
LTH
)/500 = CS1, all of the
current from CS1 is subtracted, making the TIP-RING voltage = 0 V. This is the short circuit condition. At least 100
Ω
loop and
fuse resistance are required to ensure stability of the A
i
(TIP) and B
i
(RING) output amplifiers.
The capacitor C
LPFi
, in conjunction with an internal 25 kΩ resistor (not shown), is used to create a low pass filter for the DC feed
loop. This capacitor should nominally be 4.7 µF, setting a 1.4 Hz pole. The purpose of this capacitor is to stabilize the DC feed
and filter any AC components.
Figure 3.
DC Feed Curve
V
AB
V
AB
open
(48 V)
I
LTH
I
SC
=
I
LTH
+
17.0mA
1.4 V
-
I
LTH
=
-------------------------
R
DC
K
DC
17.0 mA
0
Note:
1.
2.
3.
4.
5.
R
DC
= external resistor from RDC to AGND
V
AB
= V
Ai
– V
Bi
Tip-Ring differential voltage
I
SC
I
LOOP
1
-
K
DC
= Le9502 RSLIC device DC current gain, which is:
K
DC
=
---------
500
I
SC
= Loop short circuit current limit.
I
LTH
= Loop current limit threshold.
4
Le9502 VE950 Series Data Sheet
Figure 4.
DC Feed Block Diagram, Active and Standby Modes
VCC
CS1
I
LOOP
K
DC
R
DC
*
Current Mirrors
RDC
I
LTH
K
DC
LPF
i
R
S
C
LPFi
*
I
A
Level Shift
Polarity Control
I
B
Sum/
Sense
A
i
(TIP)
I
LOOP
R
L
R
S
B
i
(RING)
F
i
Note:
* denotes external components.
Ringing
The Le9502 RSLIC device only provides a method for creating internal ringing. Internal ringing is accomplished by applying a
single or differential ringing waveform using the VRINGP and VRINGM pins, and placing the Le9502 RSLIC device into the
ringing state via the device's control bits. When the Le9502 RSLIC device is in the Ringing state, the gain from the Le9502 RSLIC
device's differential ringing input pin to the output, is K
R
(the ringing voltage gain). The output waveform is a quasi-balanced
waveform as shown below in
Figure 5).
On the positive half cycle of the input waveform, the A
i
(TIP) lead of the Le9502 RSLIC
device is near -4 V, and the B
i
(RING) lead is brought negative. Likewise, on the negative half cycle of the input waveform, the
B
i
(RING) lead of the Le9502 RSLIC device is held near -4 V, while the A
i
(TIP) lead is brought more negative. The low cost
regulator solution, shown in the application circuit on
page 20,
incorporates the use of a higher power PNP bipolar switching
transistor in the switching circuit that enables the Le9502 to provide a 90 Vpk ringing signal into a lower REN load. The waveform
can be either sinusoidal or trapezoidal under the control of the codec device.
Figure 5.
+V
RING_pk
/ 2
Ringing Waveforms
-V
RING_pk
/ 2
VRINGM
VRINGP
A. Voltage Applied to VRING Input (VRINGP, VRINGM)
–4 V
–(K
R
• V
RING_pk
+ 4)
B. Voltage Output at A (TIP) (dashed line) and B (RING) (solid line) Pins
Le9502 VE950 Series Data Sheet
5
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