Document ID# 081195
Date:
Mar 21, 2005
Rev:
E
Version: 1
Distribution:
Public Document
Le7942B
Subscriber Line Interface Circuit
DISTINCTIVE CHARACTERISTICS
Programmable constant-current feed
Receive current gain = 500
Programmable loop-detect threshold
Low standby power
Performs polarity reversal
Ground-key detector
Pin for external ground-key noise filter capacitor
Test relay driver option
Compatible with Le7942 Device
Tip Open state for ground-start lines
19 V to 58 V battery operation
Ideal for PBX and KTS applications
On-chip switching regulator for low-power
dissipation
Can be used with or without the on-chip switching
regulator
On-hook transmission
BLOCK DIAGRAM
VTX
VREG
VBAT
15474A-001
Signal
Transmission
Input Decoder
and Control
Ground-Key
Detector
Ring Relay Driver
Test Relay Driver
C1
C2
C3
C4
E1
GKFIL
RSN
Off-Hook
Detector
Power-Feed
Controller
Ring-Trip
Detector
Switching
Regulator
TESTOUT
RINGOUT
RD
RDC
L
Two-Wire
A(TIP)
HPA
HPB
B(RING)
BGND
DA
DB
CHS
CHCLK
VCC
VEE AGND/DGND
CAS
DET
QBAT
Interface
2
Le7942B Data Sheet
ORDERING INFORMATION
Standard Products
Legerity standard products are available in several packages and operating ranges. The order number (Valid Combination) is
formed by a combination of the elements below.
Valid Combinations
Valid Combinations lists configurations planned
to be supported in volume for this device. Consult
the local Legerity sales office to confirm
availability of specific valid combinations, to
check on newly released combinations, and to
obtain additional data on Legerity's standard
militarygrade products.
Valid Combinations
Green Package
Le7942BDJC
Le7942B1DJC
Le7942B2DJC
Non-Green Package
Le7942BJC
Le7942B-1JC
Le7942B-2JC
Le7942B
J
PERFORMANCE GRADE
Blank = Standard specification
1 = Performance Grading
2 = Performance Grading
C = Commercial (0
C to 70C)*
Subscriber Line Interface Circuit
C
DEVICE NUMBER/DESCRIPTION
Le7942B
D= Green package (see note)
PACKAGING MATERIAL
Blank= Standard package
PLCC package
Note: The green package meets RoHS Directive 2002/95/EC of the European
Council to minimize the environmental impact of electrical equipment.
Le7942B Data Sheet
3
CONNECTION DIAGRAMS
Top View
Notes:
1. Pin 1 is marked for orientation.
2. TP is a thermal conduction pin tied to substrate (QBAT).
TP
TESTOUT
L
C4
VBAT
QBAT
CHS
CHCLK
E1
RINGOUT
BGND
B(RING)
A(TIP)
DB
GKF
I
L
5
6
7
8
9
10
11
12
13
29
28
27
26
25
24
23
22
21
14 15
16
17 18 19 20
4
3
2
1
32 31 30
C1
C3
C2
TP
AGND/DGND
DET
DA
RD
HPB
HPA
VTX
VBREF
RSN
CAS
RD
C
VREG
VCC
32-Pin PLCC
4
Le7942B Data Sheet
PIN DESCRIPTIONS
Notes:
1. All pins, except CHCLK, connect to VBAT when using SLIC without a switching regulator. CHCLK is connected to AGND/
DGND.
2. To prevent noise pickup by the detection circuits when using Ground-Key Detect state (E1 = logical 1), a 3300 pF minimum
bypass capacitor is recommended between the GKFIL pin and ground.
3. Each relay driver has a zener clamp to BGND.
Pin Names
Type
Description
AGND/DGND
Gnd
Analog and Digital ground.
A (TIP)
Output
Output of A(TIP) power amplifier.
BGND
Gnd
Battery (power) ground.
B (RING)
Output
Output of B(RING) power amplifier.
C3C1
Input
Decoder. TTL compatible. C3 is MSB and C1 is LSB.
C4
Input
Test Relay Driver Command. TTL compatible. A logic Low enables the driver.
CAS
Capacitor
Anti-saturation pin for capacitor to filter reference voltage when operating in anti-saturation
region.
CHCLK
Input
Chopper Clock. Input to switching regulator (TTL compatible). Freq = 256 kHz (typ).
(See Note 1).
CHS
Input
Chopper Stabilization. (See Note 1) Connection for external chopper stabilizing components.
DA
Input
Ring-trip negative. Negative input to ring-trip comparator.
DB
Input
Ring-trip positive. Positive input to ring-trip comparator.
DET
Output
Switchhook detector. When enabled, a logic Low indicates the selected detector is tripped. The
detector is selected by the logic inputs (C3C1, E1). The output is open-collector with a built-in
15 k
pull-up resistor.
E1
Input
Ground-Key Enable. E1 = High connects the ground-key detector to DET. E1 = Low connects the
off-hook or ring-trip detector to DET.
GKFIL
--
Connection for external ground-key, noise-filter capacitor. (See Note 2.)
HPA
Capacitor
High-Pass Filter Capacitor. A(TIP) side of high-pass filter capacitor.
HPB
Capacitor
High-Pass Filter Capacitor. B(RING) side of high-pass filter capacitor.
L
Output
(See Note 1)
Switching Regulator Power Transistor. Connection point for filter inductor and anode of Switching
Regulator Power Transistor. Connection point for filter inductor and anode of catch diode. Has up
to 60 V of pulse waveform on it and must be isolated from sensitive circuits. Keep the diode
connections short because of the high currents and high di/dt.
QBAT
Battery
Quiet Battery. (See Note 1). Filtered battery supply for the signal processing circuits.
RD
Resistor
Detector resistor. Detector threshold set and filter pin. May be connected to ground or -5V.
RDC
Resistor
DC feed resistor. Connection point for the DC feed current programming network. The other end
of the network connects to the receiver summing node (RSN).
RINGOUT
Output
Ring Relay Driver. Open-collector driver with emitter internally connected to BGND.
(See Note 3)
RSN
Input
Receive Summing Node. The metallic current (AC and DC) between A(TIP) and B(RING) is equal
to 500 x the current into this pin. The networks that program receive gain, two-wire impedance,
and feed current all connect to this node.
TESTOUT
Output
Test Relay Driver. Open collector driver with emitter internally connected to BGND.
(See Note 3)
TP
Thermal
Thermal pin. Connection for heat dissipation. Internally connected to substrate (QBAT). Leave as
open circuit or connected to QBAT. In both cases, the TP pins can connect to an area of copper
on the board to enhance heat dissipation.
VBAT
Battery
Battery supply.
VCC
Power
+5 V power supply.
VBREF
Power
Reference voltage. No current on the pin. May be connected to QBAT or 5 V.
VREG
Input
Regulated Voltage. (See Note 1.) Provides negative power supply for power amplifiers.
Connection point for inductor, filter capacitor, and chopper stabilization.
VTX
Output
Transmit Audio. This output is a unity gain version of the A(TIP) and B(RING) metallic voltage.
VTX also sources the two-wire input impedance programming network.
Le7942B Data Sheet
5
ABSOLUTE MAXIMUM RATINGS
Storage temperature . . . . . . . . . . . . 55
C to +150C
V
CC
with respect to AGND/DGND . . .0.4 V to +7.0 V
V
EE
with respect to AGND/DGND . . . +0.4 V to QBAT
V
BAT
with respect to AGND/DGND. . . +0.4 V to 70 V
Note: Rise time of V
BAT
(dv/dt) must be limited to 27 V/
s or
less when Q
BAT
bypass = 0.33
F.
BGND with respect to AGND/DGND .+1.0 V to 3.0 V
A(TIP) or B(RING) to BGND:
Continuous . . . . . . . . . . . . . . . . . . 70 V to +1.0 V
10 ms (f = 0.1 Hz) . . . . . . . . . . . . . 70 V to +5.0 V
1
s (f = 0.1 Hz) . . . . . . . . . . . . . . .90 V to +10 V
250 ns (f = 0.1 Hz) . . . . . . . . . . . .120 V to +15 V
Current from A(TIP) or B(RING)
. . . . . . . . . . . .150 mA
Voltage on RINGOUT, TESTOUT . . . .BGND to + 7 V
Voltage on RINGOUT, TESTOUT (transient)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BGND to +10 V
Current through relay drivers . . . . . . . . . . . . . . 60 mA
Voltage on ring-trip inputs
(DA and DB) . . . . . . . . . . . . . . . . . . . . . V
BAT
to 0 V
Current into ring-trip inputs
. . . . . . . . . . . . . . . . .10 mA
Peak current into regulator
switch (L pin). . . . . . . . . . . . . . . . . . . . . . . 150 mA
Switcher transient peak off
voltage on L pin. . . . . . . . . . . . . . . . . . . . . . +1.0 V
C4C1, E1, CHCLK to
AGND/DGND . . . . . . . . . . . .0.4 V to V
CC
+ 0.4 V
Maximum power dissipation, T
A
(see note) . . . . .70
C
In 32-pin PLCC package. . . . . . . . . . . . . . . 1.74 W
Note: Thermal limiting circuitry on chip will shut down the
circuit at a junction temperature of about 165C. The device
should never be exposed to this temperature. Operation
above 145C junction temperature may degrade device
reliability. See the SLIC Packaging Considerations for more
information.
Stresses above those listed under Absolute Maximum Ratings
cancause permanent device failure. Functionality at or above
these limits is not implied. Exposure to Absolute Maximum
Ratings for extended periods may affect device reliability.
OPERATING RANGES
Commercial (C) Devices
Ambient temperature . . . . . . . . . . . . . . 0
C to +70C*
V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . 4.75 V to 5.25 V
V
EE
. . . . . . . . . . . . . . . . . . . . . . . . . . 4.75 V to QBAT
V
BAT
. . . . . . . . . . . . . . . . . . . . . . . . . . 19 V to 58 V**
AGND/DGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V
BGND with respect to
AGND/DGND. . . . . . . . . . . . 100 mV to +100 mV
Load Resistance on VTX to ground . . . . . . 10 k
min
The Operating Ranges define those limits between which the
functionality of the device is guaranteed.
*Legerity guarantees the performance of this device over
commercial (0 to 70C) and industrial (-40 to 85 C)
temperature ranges by conducting electrical characterization
over each range and by conducting a production test with
single insertion coupled to periodic sampling. These
characterization and test procedures comply with section
4.6.2 of Bellcore TR-TSY-000357 Component Reliability
Assurance Requirements for Telecommunications
Equipment.
**
Can be used without switching regulator components in this
range of battery voltages, provided maximum power
dissipation specifications are not exceeded.
Package Assembly
The non-green package devices are assembled with
industry-standard mold compounds, and the leads
possess a tin/lead (Sn/Pb) plating. These packages
are compatible with conventional SnPb eutectic solder
board assembly processes. The peak soldering
temperature should not exceed 225C during printed
circuit board assembly.
The green package devices are assembled with
enhanced environmental compatible lead-free,
halogen-free, and antimony-free materials. The leads
possess a matte-tin plating which is compatible with
conventional board assembly processes or newer
lead-free board assembly processes. The peak
soldering temperature should not exceed 245C during
printed circuit board assembly.
Refer to IPC/JEDEC J-Std-020B Table 5-2 for the
recommended solder reflow temperature profile
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