3

Block Diagram

TPG

TP

CS

GND

HKS

LS

DP

H = ON

L = OFF

Charge Pump

&

Logic Control

(1)

(2)

(5)

(6) for HT18

(6) for HT19

(8)

(7)

(3)

DP

Pin Description

Pin # Symb

Description

1

TPG

Positive input side of a telephone line, typically Tip side.

2

HKS

Hookswitch input. Connect HKS to TPG to turn on the hook switch. Internally pulled low with a high value resistor.

3

GND

Device ground. Negative side of a telephone line, typically Ring side.

4NC

No Connect. Open Circuit. No internal connections to the device.

5LS

Line switch input. Input logic high turns on the hook switch. Internally pulled low with a high value resistor.

6DP

For HT18. Dial pulse input. Input logic high turns off the hook switch. Used for pulse dialing. Internally pulled low with a

high value resistor.

6DP

For HT19. Dial pulse input. Input logic low turns off the hook switch. Used for pulse dialing. Internally pulled high with a

high value resistor.

7CS

Current sense input. An external resistor connected between CS and TP sets the current limit.

8TP

Positive output side of a telephone line. Zener protection to prevent this output from rising above 18V is required.

HT18/HT19

Typical Application Circuit

Tip

Ring

Transient

Protection

TPG

HKS

GND

DP/DP

LS

CS

15V

HT18

or

HT19

Telecom

Circuit

TP

1235 Bordeaux Drive, Sunnyvale, CA 94089

TEL: (408) 744-0100 • FAX: (408) 222-4895

www.supertex.com

12/13/010

©2001 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.