The TCM1520A is a monolithic ring-detection
integrated circuit designed for use in isolated or
nonisolated telephone applications. The device
uses a modified form of the Texas Instruments
BIDFET
CMOS and high-voltage bipolar input/output
circuitry. It features efficient high-voltage (40 V to
150 V) operation with a typical current drain of
1 mA.
During standby, the input impedance is
approximately 1 MΩ or greater, which prevents
any interference with parallel off-hook telephones
transmitting DTMF or voice frequencies. The
device achieves this high input impedance with an
on-chip series zener diode that does not conduct
until the voltage across AC INPUT (pins 1 and 8)
exceeds 8 V . When the voltage across pins 1 and
8 exceeds 18 V , the internal switch is closed, which bypasses the 6.8-V zener diode series resistor . This allows
more efficient power transfer to the load when the device is in the operating mode. In the operating mode, the
impedance of the device varies from 30 kΩ to 7 kΩ over the ring signal of 40 V at 16 Hz to 150 V at 68 Hz and
is reasonably independent of the output load.
†
technology to combine low-voltage
‡
The D package is available taped and reeled with suffix R
added to the device type (i.e., TCM1520ADR).
TCM1520A APPLICATION
Phone Line
TCM1520A
Electronic Telephone
or Accessory
TTL/NMOS/CMOS
Microprocessor
AVAILABLE OPTIONS
T
A
SMALL OUTLINE
TCM1520ADTCM1520AP–40°C to 85°C
AC Ring
Signal
‡
(D)
PACKAGE
PLASTIC DIP
(P)
In typical telephone applications, the TCM1520A is activated through the telephone line by a ring voltage of 40 V
at 16 Hz to 150 V at 68 Hz. The TCM1520A generates a signal suitable to drive an optocoupler or TTL, NMOS,
or CMOS logic. The 5-V OUTPUT can be used as a supply source for optocouplers or low-power logic. This
output is noninverting and is at a high level during ringing.
The TCM1520A incorporates lightning and transient protection that is designed to withstand lightning strikes
of 1.5-kV amplitude and 200-µs duration and also features built-in circuitry to avoid tapping or false triggering
due to transients.
Caution. These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive
foam during storage or handling to prevent electrostatic damage to the MOS gates.
†BIDFET – Bipolar, double-diffused, N-channel and P-channel MOS transistors on same chip. This is a patented process.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
POST OFFICE BOX 1443
• HOUSTON, TEXAS 77251–1443
Copyright 1990, Texas Instruments Incorporated
1
TCM1520A
DUAL DIFFERENTIAL COMPARATORS
SCTS005B – OCTOBER 1984 – REVISED DECEMBER 1990
functional block diagram
AC INPUT
AC INPUT
1
8
Transient
Protection
Section
Ring-Signal
Voltage Input
Section
45 V1A
Current
Sensor
Output Section
Regulated
Voltage
V
ref
5-V Series
Regulator
High-Input Impedance/
Antitapping Section
6.8 V
200 Ω
8 kΩ
18 kΩ
5
BELL TAPPING
SENSE
6
C FILTER
4
5-V OUTPUT
2
INVERTING
OUTPUT
37
COMMONCOMMON
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
†
Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: All voltage values, unless otherwise noted, are with respect to COMMON (pin 7).
Input voltage, VIrms (f = 15.3 Hz to 68 Hz) (see Note 2)40150V
Operating free-air temperature, T
NOTE 2: Input voltage is applied to AC INPUT (pins 1 and 8) through a series 2.2-kΩ± 10% resistor and a 0.47-µF ±10% capacitor. (see
Figures 1, 4, and 5.)
A
electrical characteristics over recommended operating free-air temperature range, RL = open,
C
= 10 µF (unless otherwise noted)
(fltr)
detector section
PARAMETER
V
(BR) CEX
V
OL
V
IT+
V
IT–
V
hys
V
I(on)
V
O
Z
I(off)
I
I(on)
I
I(hold)
†
All characteristics are measured with a 2.2-kΩ resistor and a 0.47-µF capacitor connected at AC INPUT (pin 1) in series with the input signal,
unless otherwise noted.
‡
All typical values are at TA = 25°C.
NOTES: 3. These parameters are measured using pulse techniques (tw ≤ 200 µs, duty cycle ≤ 5%) with C FILTER grounded.