HT18/ HT19 Electronic Telephone Line Switch Features 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 their off state, they can withstand 350V on the positive input. In their on state, they have a maximum series resistance of 18Ω. 350V breakdown voltage 18Ω maximum switch resistance Current limiting protection Operates at 2.3V input Applications ► ► ► ► ► ► Telephone handsets Modems Fax machines Answering machines Remote meter reading Telephone interface products 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). Typical Application Circuit TPG TP Tip RSEN Transient Protection HKS HT18 or HT19 CS 15V LS DP/DP Ring GND Telecom Circuit HT18/HVT19 Ordering Information Package Options Device 8-Lead SOIC (Narrow Body) HT18 HT18LG HT18LG-G HT19 HT19LG HT19LG-G -G indicates package is RoHS compliant (‘Green’) Absolute Maximum Ratings Pin Configuration Parameter Value TPG 1 VTPG, Input line voltage +350V VTP, Output line voltage +18V DP/DP continuous input voltage +10V Storage temperature GND 3 7 CS 6 DP/DP 5 LS SO-8 Note 1. For HT18, Pin 6 is DP For HT19, Pin 6 is DP +300°C Power dissipation TP (Top View) +150°C 1 HT18/ HT19 NC 4 -65°C to +150°C Junction temperature Soldering temperature HKS 2 8 0.8W Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is not implied. Continuous operation of the device at the absolute rating level may affect device reliability. All voltages are referenced to device ground. Note 1. Distance of 1.6mm from case for 10 seconds. Electrical Characteristics (T =25°C unless otherwise specified) J Symbol Parameter VTPG High voltage positive supply ITPQ Input leakage current RSW TPG to TP switch resistance Min Typ Max Units - - 350 V - - 2.0 - - 200 - - 18 - - 18 - - 30 - - 75 - - 100 µA Conditions ITPG = 500µA, HKS, LS, DP/DP = open circuit VTPG = 100V, HKS, LS, DP/DP = open circuit VTPG = 290V, HKS, LS, DP/DP = open circuit VTPG = 17V, ITPG = 180mA, SW = On Ω VTPG = 3.0V, ITPG = 20mA, SW = On VTPG = 2.3V, ITPG = 5mA, SW = On Bias current ILIM ITPG current limiting 188 250 330 mA REXT = 200Ω ± 1% IHKS HKS input current - - 200 µA VHKS = 40V -70V ILS, IDP LS and DP logic input current - - 30 µA VLS = 3.0V, VDP = 3.0V IDP DP output current - - -30 µA VDP = 0V 2 µA VTPG = 5.0V, SW = On ITPG - ITP VTPG = 10V, SW = On HT18/HVT19 Electrical Characteristics Symbol Parameter Min Typ Max Unit VIL(HKS) Conditions HKS input low 0 - 0.2 V VTPG = 3.0V to 70V VIH(HKS) HKS input high 2.0 - VTPG V VTPG = 3.0V to 70V VIL(LS), VIL(DP) Input logic low for DP/DP and LS 0 - 0.2 V VTPG = 3.0V to 70V VIH(LS), VIH(DP) Input logic high for DP/DP and LS 1.5 - 10 V VTPG = 3.0V to 70V TON Turn on time - - 1.0 ms VTPG = 4.5V TOFF Turn off time - - 1.0 ms VTPG = 4.5V Logic Truth Table HKS LS1 DP DP Switch State H L or Z L or Z H or Z ON H H L or Z H or Z ON L or Z L or Z L or Z H or Z OFF L or Z H L or Z H or Z ON X X H L OFF Z = high impedance, open circuit X = don’t care L = logic level low H = logic level high Block Diagram (1) (8) TP TPG (2) HKS H = ON L = OFF (5) (7) CS Charge Pump and Logic Control LS (6) for HT18 DP (3) GND (6) for HT19 DP 3 HT18/HT19 Pin Description Pin Name 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. 4 NC No Connect. Open Circuit. No internal connections to the device. 5 LS Line switch input. Input logic high turns on the hook switch. Internally pulled low with a high value resistor. 6 DP 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. 6 DP 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. 7 CS Current sense input. An external resistor connected between CS and TP sets the current limit. 8 TP Positive output side of a telephone line. Zener protection to prevent this output from rising above 18V is required. 8-Lead SOIC (Narrow Body) LG Package Outline 4.90 ± 0.10 8 6.00 ± 0.20 Note 2 3.90 ± 0.10 1 5° - 15° (4 PLCS) Top View 0.17 - 0.25 0.25 - 0.50 45° Note 2 1.25 MIN 1.75 MAX 0° - 8° 0.40 - 1.27 0.10 - 0.25 1.27BSC 0.31 - 0.51 End View Side View Notes: 1. All dimensions in millimeters. Angles in degrees. 2. If the corner is not chamfered, then a Pin 1 identifier must be located within the area indicated. (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to http://www.supertex.com/packaging.html.) Doc.# DSFP-HT18_HT19 A111006 4