TCM1520A

RING DETECTOR

SCTS005B – OCTOBER 1984 – REVISED DECEMBER 1990

Copyright

1

POST OFFICE BOX 655303

POST OFFICE BOX 1443

CMOS

description

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

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 M

Ω 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 k

Ω 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.

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.

1

2

3

4

8

7

6

5

AC INPUT

INVERTING OUTPUT

COMMON

5-V OUTPUT

AC INPUT

COMMON

C FILTER

BELL TAPPING SENSE

D OR P PACKAGE

(TOP VIEW)

TCM1520A APPLICATION

Phone Line

AC Ring

Signal

TCM1520A

Electronic Telephone

or Accessory

TTL /NMOS/CMOS

Microprocessor

AVAILABLE OPTIONS

PACKAGE

SMALL OUTLINE

(D)‡

PLASTIC DIP

(P)

TCM1520AD

TCM1520AP

–40

°C to 85°C

TA

‡ The D package is available taped and reeled with suffix R

added to the device type (i.e., TCM1520ADR).

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.