L3845
TRUNK INTERFACE
ON CHIP POLARI TY GUARD
MEETS DC LINE CHARACTERISTICS OF
EITHER CCITT AND EIA RS 464 SPE CS
PULS E FUNCTION
HIGH AC IMPEDA NCE
OFF HOOK-STATU S DETECTION OUTPU T
LOW EXT E RNAL COMPO NE NT COU NT
DESCRIPTION
The circuit provides DC loop termination for ana-
log trunk lines.
The V-I characteristics is equivalent to a fixed
voltage drop (zener like characteristic) in series
with an external resistance that determines the
slope of the DC characteristic.
An external low voltage electrolytic capacitor
causes the circuit to exhibit a very high imped-
ance to all AC signal abov e a m inim um frequency
that is determined by the capacitor itself and by a
20 K nominal resistor integrated on the chip.
The Off-Hook status is detected all the time a
typic of 8 mA is flowing into the circuit. In this con-
dition a constant current generator is activated to
supply an external device (typically an optocou-
pler) without affecting the AC characteristic of the
circuit.
When Pulse Dialing is required the PULSE input
(pin 3) connected to V- causes the device to re-
duce the fixed DC voltage drop and to exhibit a
pure resistive impedance equal to the external re-
sistor.
This is advanced information on a new product now in development or undergoing evaluation. Details are subject to change without no tice .
September 2003
®
POLARITY
GUARD
DC LINE
TERMINATION OF HOOK
DETECTION
CIRCUIT
1
7
8
3
4
IN1
IN2
562
ACT DCT V-
R2 R3
R1
S1 C1
S2
V+
PULSE
HD0
D96TL263
BLOCK DIAGRAM
Minidip SO8 SO20W
(12+4+4)
ORDERING NUMBERS:
L3845B L3845D L3845-20
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ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
VLMax Line Voltage (pulse duration 10 ms max) 20 V
ILMax Line Current 150 mA
Ptot Total Power Dissipation at Tamb = 70 °C800mW
T
op Operating Temperature – 40 to + 70 °C
Tsrg, TjStorage and Junction Temperature – 55 to + 150 °C
THERMAL DATA
Symbol Parameter Minidip SO8 SO20 Unit
Rth j-amb Thermal Resistance Junction-ambient (*) Max. 80 140 to 180 50 to 70 °C/W
(*) Mounted on FR4 Boards
PIN C ONNECTION (Top view)
PULSE
HD0
NC
SUBS
SUBS
SUBS
SUBS
NC
ACT V+
NC
SUBS
SUBS
SUBS
SUBS
NC
IN1
V-1
3
2
4
5
6
7
8
9
18
17
16
15
14
12
13
11
19
10
20
DCT IN2
SO20
SO20
IN1
V-
PULSE
HD0
1
3
2
4 ACT
DCT
IN2
V+8
7
6
5
DIP8
MINIDIP and SO8
SUBS = t he pin is electrically and thermally in good contact with the chip sustrate. Connect to PCB copper tracks, for heat dissipation the
tracks shall preferably be electrically connected to pin 20 (internally bonded to the chip substrate) or left floating. A higher tra ck
density and/or area assures a Rth j-amb towards the lower limit.
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DC ELECTRICAL CHARACTERISTICS (IL = 10 mA to 100 mA, R1 = 56 Ω, S1 = Ope n, Tamb = + 25 °C,
unless otherwise specified)
Symbol Parameter Test Condition Min. Typ. Max. Unit
VLLine Voltage
(normal mode) PULSE = Open
IL = 10 mA
IL = 20 mA
IL = 100 mA
5
6
12
V
V
V
VLP Line Voltage
(pulse mode) PULSE = V–
IL = 20 mA
IL = 35 mA
IL = 80 mA
4
5.5
9.5
V
V
V
Ihn ON/OFF-Hook
Line Current Detection
Threshold
6.5 9.5 mA
Ihf OFF/ON-Hook
Line Current Detection
Threshold
59.2mA
I
OUT OFF-Hook
Output Drive Current at Pin
HDO
IL = 10 mA
IL ≥ 20 mA 1.5
1.8 mA
mA
VPM Pulse Input Low Voltage 0.8 V
IPM Pull-up Input Current at Pin
PULSE (pulse mode) IL = 100 mA
Pulse = V–20 µA
INM Imput Current at Pin Pulse
(normal mode) 3µA
AC ELECTRICAL CHARACTERISTICS (IL = 10mA to 10 0mA, R1 = 56Ω, R2 = 470KΩ, R3 = 130 KΩ,
Tamb = + 25 °C, unless otherwise specified)
Symbol Parameter Test Condition Min. Typ. Max. Unit
ZLAC Line Impedance S1 = Open, S2 = Open
C1 = 2.2mF
f = 1KHz 20 KΩ
Sending/Receiving Distortion S1 = Open, S2 = Open
f = 1KHz
VAC-L = 775mVrms
IL = 15 to 100mA 2%
Sending/Receiving Distortion S1 = Closed; S2 = Open
VAC-L = 1.3Vrms 2 %
Sending/Receiving Distortion S1 = Open; S2 = Closed
VAC-L = 1.9Vrms 2(*) %
(*) Not tested, guaranteed only by design.
APPLICAT ION IN FOR MATION
With the use of this circuit it is possible to termi-
nate an analog trunk so that all the DC current
component is flowing in the TRUNK TERMINA-
TION CIRCUIT while the AC component is de-
coupled with a low voltage capacitor and can be
used with a small and low cost audio coupler
transformer to provide the AC balancing termina-
tion and two to four wire conversion.
Therefor e it is usefull both for M ODEM and PABX
systems.
Figure 1 gives the typical application circuit ; it is
worth to note that the TRUNK TERMINATION
CIRCUIT, together with the LS5018 transient sup-
pressor provides a compact and low cost module
fully protected against lightning or overvoltages
frequently present on telephone lines.
The PULSE input when connected to V- allows
the device to reduce the Line Voltage and to
show a resistive impedance equal to R1 to the
line. When PULSE input is left open, this function
is disable.
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Figure 1: Typical Application.
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OUTLINE AND
MECHANICAL DATA
DIM. mm inch
MIN. TYP. MAX. MIN. TYP. MAX.
A 3.32 0.131
a1 0.51 0.020
B 1.15 1.65 0.045 0.065
b 0.356 0.55 0.014 0.022
b1 0.204 0.304 0.008 0.012
D 10.92 0.430
E 7.95 9.75 0.313 0.384
e2.54 0.100
e3 7.62 0.300
e4 7.62 0.300
F 6.6 0.260
I 5.08 0.200
L 3.18 3.81 0.125 0.150
Z 1.52 0.060
Minidip
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DIM. mm inch
MIN. TYP. MAX. MIN. TYP. MAX.
A 1.75 0.069
a1 0.1 0.25 0.004 0.010
a2 1.65 0.065
a3 0.65 0.85 0.026 0.033
b 0.35 0.48 0.014 0.019
b1 0.19 0.25 0.007 0.010
C 0.25 0.5 0.010 0.020
c1 45° (typ.)
D (1) 4.8 5.0 0.189 0.197
E 5.8 6.2 0.228 0.244
e 1.27 0.050
e3 3.81 0.150
F (1) 3.8 4.0 0.15 0.157
L 0.4 1.27 0.016 0.050
M 0.6 0.024
S8° (max.)
(1) D and F do not include mold flash or protrusions. Mold flash or
potrusions shall not exceed 0.15mm (.006inch).
SO8
OUTLINE AND
MECHANICAL DATA
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110
1120
A
e
B
D
E
L
KH
A1 C
SO20MEC
h x 45˚
SO20
DIM. mm inch
MIN. TYP. MAX. MIN. TYP. MAX.
A 2.35 2.65 0.093 0.104
A1 0.1 0.3 0.004 0.012
B 0.33 0.51 0.013 0.020
C 0.23 0.32 0.009 0.013
D 12.6 13 0.496 0.512
E 7.4 7.6 0.291 0.299
e 1.27 0.050
H 10 10.65 0.394 0.419
h 0.25 0.75 0.010 0.030
L 0.4 1.27 0.016 0.050
K 0˚ (min.)8˚ (max.)
OUTLINE AND
MECHANICAL DATA
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Information f urnish ed is believ ed to be accurat e and reliable. Howev er, STM icroele ctronics ass umes no respons ibilit y for the cons equences
of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is
granted by impl ication or ot herwis e under any pa tent or patent right s of STMi croelect ronics. Spec ifications mentioned i n this publ ication are
subject t o change witho ut notice. This publication s upersedes and re places all infor mation previ ously suppli ed. STMicroel ectron ics produc ts
are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.
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