HT18LG

HT18 HT19 Electronic Telephone Line Switch Ordering Information Package Option Breakdown Voltage 350V 350V Switch Resistance 18Ω 18Ω Dial Pulse Pin DP/DP Active High Active Low SO-8 HT18LG HT19LG Features ❏ 350V breakdown voltage ❏ 18Ω maximum switch resistance ❏ Current limiting protection ❏ Operates at 2.0V input 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). Applications ❏ Telephone handsets ❏ Modems ❏ Fax machines ❏ Answering machines ❏ Remote meter reading ❏ Phone interface products Pin Configuration Absolute Maximum Ratings VTPG, Input line voltage VTP, Output line voltag...