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HT18

HT19

Electronic Telephone Line Switch

General Description

The Supertex HT18LG and HT19LG are electronic line switch

circuits that replace the mechanical hook switch contact or a

discrete hook switch in a telephone handset or modem. They

switch the positive side of the telephone line using control inputs

that are referenced to the negative side of the line. In the off state,

they can withstand 350V on the positive input. In the on state

their series resistances are 18Ω maximum. The devices provide

current limiting determined by an external resistor. There are

three control inputs. The HKS pin turns on the hook switch when

connected to the TPG pin. This can be accomplished by using a

mechanical switch which closes when the handset is physically

off-hook. The LS pin allows a logic signal to turn on the hook

switch. The dial pulse, Pin 6, is used to turn the hook switch off

for pulse dialing. For the HT18, the dial pulse is active high (DP)

whereas for the HT19, it is active low (DP).

Features

❏ 350V breakdown voltage

❏ 18Ω maximum switch resistance

❏ Current limiting protection

❏ Operates at 2.0V input

Applications

❏ Telephone handsets

❏ Modems

❏ Fax machines

❏ Answering machines

❏ Remote meter reading

❏ Phone interface products

Absolute Maximum Ratings

V

+350V

V

+18V

DP/DP continuous input voltage

+10V

Storage temperature

–65°C to +150°C

Junction temperature

+150°C

Soldering temperature*

+300°C

Power dissipation

0.8 Watt

Notes: All voltages are referenced to ground.

*Distance of 1.6mm from case for 10 seconds.

1

2

3

4

8

7

6

5

Pin Configuration

TPG

TP

HKS

CS

GND

DP/DP *

N/C

LS

Note: See Package Outline section for dimensions.

top view

SO-8

Package Option

Dial Pulse Pin

SO-8

Breakdown Voltage

Switch Resistance

DP/DP

350V

18Ω

Active High

HT18LG

350V

18Ω

Active Low

HT19LG

Ordering Information

* For HT18, Pin 6 is DP.

For HT19, Pin 6 is DP.

12/13/01

Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products liability

indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be defective due to

workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the

Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer page on the Supertex website.