ISL5571A ® Data Sheet January 2004 Access High Voltage Switch Features The ISL5571A is a solid state device designed to replace the electromechanical relay used on Subscriber Line Cards. The device contains two Line Break MOSFET switches, one Ring Return MOSFET switch and one Ring Access SCR switch. • Small Size/Surface-Mount Packaging The ISL5571A is pin-for-pin compatible with the Lucent L7581AAE LCAS and Clare CPCL7581A Products. Improvements include: line break switches rON match (0.5Ω Max) higher dV/dt sensitivity (5000V/µs), protection SCR hold current set to 110mA. FN4920.4 • Low Impulse Noise, Low EMI • Clean, Bounce-Free Switching • Line Break Switches - 0.5Ω Max rON Match - 28Ω Max rON • Built-In Current Limiting, Thermal Shutdown and Secondary Protection for the SLIC The line break MOSFETs have very low on resistance (<16.0Ω Typ) and Ron match (<0.05Ω Typ, 0.5Ω Max) and a blocking voltage >330V. The Ring Return MOSFET has a typical Ron of 50Ω and a blocking voltage >330V. The Ringing Access switch is implemented with a SCR device with a blocking voltage >480V. The SCR switch inherently offers low EMI connect and disconnect circuitry. All control I/Os use TTL thresholds making the device compatible with 3V logic. • Optimized for Short Loop High REN Applications The ISL5571A also includes on-chip protection in the form of an over-voltage clamping circuit, current-limited MOSFET switches, and thermal shutdown circuitry. The over-voltage clamping circuit consists of a diode bridge and SCR. Related Literature Ordering Information PART NUMBER ISL5571AIB PROT SCR TEMP RANGE (oC) Yes -40 to 85 • 3V/5V Logic-Capable I/O Applications • Central Office • HFC • PBX • FITL • DLC • DAML • Technical Brief TB363 “Guidelines for Handling and Processing Moisture Sensitive Surface Mount Devices (SMDs)” • Technical Brief TB379 “Thermal Characterization of Packages for ICs” PACKAGE TYPE 16 Ld SOIC PKG. DWG. # • Texas Instruments TISPL758LF3D Data Sheet M16.3 • Teccor Electronics Document DO-214AA Pinout ISL5571A TOP VIEW FGND 1 16 VBAT TBAT 2 15 RBAT TLINE 3 14 RLINE NC 4 13 NC NC 5 12 RRING 11 LATCH TRING 6 VDD 7 10 INPUT TSD 8 9 DGND 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright © Intersil Americas Inc. 2004. All Rights Reserved All other trademarks mentioned are the property of their respective owners. ISL5571A Block Diagram ISL5571A - 16 LEAD SOIC VBAT TRING 16 6 LINE BREAK SW1 TLINE 3 2 TBAT RING RETURN SW3 D1 D3 SCR RLINE 14 RING ACCESS SW4 D2 1 FGND D4 15 RBAT LINE BREAK SW2 7 VDD CONTROL LOGIC 12 RRING 2 11 10 9 8 LATCH INPUT DGND TSD ISL5571A Absolute Maximum Ratings TA = 25oC Thermal Information Maximum Supply Voltages (VDD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to +7V (VBAT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -19V to -100V ESD Rating (Human Body Model) . . . . . . . . . . . . . . . . . . . . . . .500V Thermal Resistance (Typical, Note 1) Die Characteristics θJA (oC/W) SOIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Maximum Junction Temperature Plastic . . . . . . . . . . . . . . . . .150oC Maximum Storage Temperature Range . . . . . . . . . -65oC to 150oC Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . .300oC (SOIC - Lead Tips Only) Substrate Potential. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VBAT Process . . . . . . . . . . . . . . . . . . . . . . . .6-inch BIMOS Bonded Wafer CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. NOTE: 1. θJA is measured with the component mounted on a low effective thermal conductivity test board in free air. See Tech Brief TB379 for details. TA = -40oC to 85oC, Unless Otherwise Specified Electrical Specifications TABLE 1. BREAK SWITCHES - ISL5571A - SW1, SW2 PARAMETER OFF-State Leakage Current: -40oC 25oC 85oC ON-Resistance: -40oC 25oC 85oC TEST CONDITION VSWITCH (DIFFERENTIAL) = -310V to GND VSWITCH (DIFFERENTIAL) = -60V to +250V VSWITCH (DIFFERENTIAL) = -320V to GND VSWITCH (DIFFERENTIAL) = -60V to +260V VSWITCH (DIFFERENTIAL) = -330V to GND VSWITCH (DIFFERENTIAL) = -60V to +270V TLINE = ±10mA, ±40mA, TBAT = -2V TLINE = ±10mA, ±40mA, TBAT = -2V TLINE = ±10mA, ±40mA, TBAT = -2V MEASURE MIN TYP MAX UNITS ISWITCH - - 1 µA ISWITCH - - 1 µA ISWITCH - - 1 µA ∆VON ∆VON ∆VON - 12 16 - 28 Ω Ω Ω 0.05 0.5 Ω - - 220 VPeak ON-Resistance Match Per ON-resistance Test Condition of SW1, SW2 Magnitude rON SW1 - rON SW2 ON-State Voltage (Note 2) Break Switches in ON-State; Iswitch = ILIMIT at 50/60Hz VON VSWITCH (ON) = ±10V VSWITCH (ON) = ±10V VSWITCH (ON) = ±10V ISWITCH ISWITCH ISWITCH 80 125 - 250 - mA mA mA Break Switches in ON-state; Ringing Access Switches OFF; Apply ±1000V at 10/1000µs Pulse; Appropriate External Secondary Protection in Place ISWITCH - 1.5 2.0 A VSWITCH (Both Poles) = ±310V Logic Inputs = GND VSWITCH (Both Poles) = ±320V Logic Inputs = GND VSWITCH (Both Poles) = ±330V Logic Inputs = GND ISWITCH - - 1 µA ISWITCH - - 1 µA ISWITCH - - 1 µA - 5000 - V/µs DC Current Limit: -40oC 25oC 85oC Dynamic Current Limit (t = <0.5µs) Isolation: -40oC 25oC 85oC dV/dt Sensitivity (Note 3) NOTES: 2. Choice of secondary protection should ensure this rating is not exceeded. 3. Applied voltage is 100VP-P square wave at 100Hz. 3 ISL5571A TABLE 2. RING RETURN SWITCH - ISL5571A - SW3 PARAMETER OFF-State Leakage Current: -40oC 25oC 85oC DC Current Limit -40oC TEST CONDITION MEASURE MIN TYP MAX UNIT S VSWITCH (DIFFERENTIAL) = -310V to GND VSWITCH (DIFFERENTIAL) = -60V to +250V VSWITCH (DIFFERENTIAL) = -320V to GND VSWITCH (DIFFERENTIAL) = -60V to +260V VSWITCH (DIFFERENTIAL) = -330V to GND VSWITCH (DIFFERENTIAL) = -60V to +270V ISWITCH - - 1 µA ISWITCH - - 1 µA ISWITCH - - 1 µA VSWITCH (ON) ISWITCH - - 350 mA VSWITCH (ON) VSWITCH (ON) ISWITCH - 200 - mA ISWITCH 120 - - mA Dynamic Current Limit (t = <0.5µs) Break Switches in OFF-State; Ringing Access Switches ON; Apply ±1000V at 10/1000µs Pulse; Appropriate External Secondary Protection in Place ISWITCH - 1.5 2.0 A ON-Resistance TLINE = 0, ±10mA ∆VON - - 100 Ω ON-State Voltage (Note 4) Ring Return Switch in ON-State; Iswitch = ILIMIT at 50/60Hz VON - - 130 VPeak VSWITCH (Both Poles) = ±310V Logic Inputs = GND VSWITCH (Both Poles) = ±320V Logic Inputs = GND VSWITCH (Both Poles) = ±330V Logic Inputs = GND ISWITCH - - 1 µA ISWITCH - - 1 µA ISWITCH - - 1 µA - 5000 - V/µs 25oC 85oC Isolation: -40oC 25oC 85oC dV/dt Sensitivity (Note 5) NOTES: 4. Choice of secondary protection should ensure this rating is not exceeded. 5. Applied voltage is 100VP-P square wave at 100Hz. TABLE 3. RING ACCESS SWITCH - ISL5571A - SW4 PARAMETER OFF-State Leakage Current: -40oC 25oC 85oC ON-Resistance TEST CONDITION MEASURE MIN TYP MAX UNITS VSWITCH (DIFFERENTIAL) = -245V to +210V VSWITCH (DIFFERENTIAL) = +245V to -210V VSWITCH (DIFFERENTIAL) = -255V to +210V VSWITCH (DIFFERENTIAL) = +255V to -210V VSWITCH (DIFFERENTIAL) = -270V to +210V VSWITCH (DIFFERENTIAL) = +270V to -210V ISWITCH - - 1 µA ISWITCH - - 1 µA ISWITCH - - 1 µA ISWITCH (ON) = ±70mA, ±80mA ∆VON - - 12 Ω ON Voltage ISWITCH (ON) = ±1mA VON - - 3 V Ring Access Switch Quiescent Current During Ringing VCC = 5V, Ring Access Switches On, All Other Switches Off IRING QUIESCENT (Note 6) - 2.0 - mA mA Steady State Current (Note 7) Surge Current (Note 7) - - 150 - - 2 A 200 - 1000 µA ISWITCH - - 1 µA ISWITCH - - 1 µA ISWITCH - - 1 µA - 5000 - V/µs Ring Access Switch On, Time Duration = 100µs Release Current Isolation: -40oC 25oC 85oC VSWITCH (Both Poles) = ±310V Logic Inputs = GND VSWITCH (Both Poles) = ±320V Logic Inputs = GND VSWITCH (Both Poles) = ±330V Logic Inputs = GND dV/dt Sensitivity (Note 8) NOTES: 6. Magnitude of the ring generator current not supplied to the ring load. IRING QUIESCENT= IRING GEN - IRING LOAD. 7. Choice of secondary protector and series current-limit resistor should ensure these ratings are not exceeded. 8. Applied voltage is 100VP-P square wave at 100Hz. 4 ISL5571A TABLE 4. LOGIC I/O ELECTRICAL CHARACTERISTICS - ISL5571A PARAMETER TEST CONDITION Digital Input Characteristics: Input Low Voltage Input High Voltage Input Leakage Current (High) Input Leakage Current (Low) MEASURE VDD = 5.5V, VBAT = -75V, VLOGIC-IN = 5V VDD = 5.5V, VBAT = -75V, VLOGIC-IN = 0V MIN TYP MAX UNITS 2.4 - - 0.8 1 1 V V µA µA MIN TYP MAX UNITS IDD, IBAT IDD, IBAT IDD - 6.6 8.8 11.0 8.5 11.5 18.2 mW mW mW IDD IDD IDD - 1.2 1.6 2.0 2.0 2.1 3.3 mA mA mA IBAT IBAT IBAT - 1.0 1.0 1.0 10 10 10 µA µA µA 115 7 125 14 135 21 oC oC ILOGIC-IN ILOGIC-IN TABLE 5. LOGIC I/O POWER REQUIREMENTS - ISL5571A PARAMETER TEST CONDITION Power Requirements: Power Dissipation VDD = 5.5V, VBAT = -48V, Idle/Talk State All OFF-State Ringing State VDD = 5.5V, Idle/Talk State All OFF-State Ringing State VBAT = -48V, Idle/Talk State All OFF-State Ringing State VDD Current VBAT Current Temp. Shutdown Requirements (Note 9) Shutdown Activation Temperature Shutdown Circuit Hysteresis MEASURE TJ NOTE: 9. The Temperature Shutdown logic pin (TSD) will be high during normal operation and low during temperature shutdown state. TABLE 6. ELECTRICAL SPECIFICATION - PROTECTION CIRCUITRY - ISL5571A PARAMETER TEST CONDITION MEASURE MIN TYP MAX UNITS Forward Voltage - - 3 V Voltage Drop at Surge Current Apply ±Dynamic Current Limit of Break Switches Forward Voltage - 5 - V - - 4 A - 50 - mA 110 - VBAT - 4V - VBAT - 2V V PARAMETERS RELATED TO DIODES Voltage Drop at Continuous Current (50Hz/60Hz) Apply ±DC Current Limit of Break Switches PARAMETERS RELATED TO PROTECTION SCR Surge Current Twice ±Dynamic Current Limit of Break Switches Gate Trigger Current -VBAT Current Hold Current mA Gate Trigger Voltage Trigger Current Reverse Leakage Current VBAT - - 1.0 µA ON-state Voltage (Note 10) 0.5A, t = 0.5µs 2.0A, t = 0.5µs - -3 -5 - V V NOTES: 10. In some instances, the typical ON-state voltage can range as low as -25V. TABLE 7. POWER SUPPLY SPECIFICATIONS SUPPLY MIN TYP MAX UNITS VDD 4.5 - 5.5 V VBAT -19 - -72 V 5 ISL5571A TABLE 8. PIN DESCRIPTIONS - ISL5571A PIN NO. PIN NAME PIN NO. PIN NAME 1 FGND Fault Ground. Internally, this pin is electrically isolated from DGND. 16 VBAT Battery Voltage. Used as a reference for protection circuit. Provides Trigger current for the protection SCR. 2 TBAT Connect to TIP on SLIC side. 15 RBAT Connect to RING on SLIC side. 3 TLINE Connect to TIP on line or phone side. 14 RLINE Connect to RING on line or phone side. 4 NC No Connection. 13 NC 5 NC No Connection. 12 RRING Connect to ringing generator. 6 TRING Connect to Return Ground for Ringing Generator. 11 LATCH Logic State Latch Control, active-high, transparent low. 7 VDD +5V supply. 10 INPUT Logic Level Input Switch Control. 8 TSD Temperature Shutdown Pin. Can be used as a logic level input or output. See Truth Table. As an output, will read +5V when device is in its operational mode and 0V in the thermal shutdown mode. In the ISL5571A, the thermal shutdown mechanism cannot be disabled. 9 DGND Digital Ground. Internally, this pin is electrically isolated from FGND. DESCRIPTION DESCRIPTION No Connection. Pinout ISL5571A TOP VIEW - 48 VDC TRING VBAT 16 6 TIP TLINE R1 VBAT RING RETURN SW3 TBAT TIP LINE BREAK SW1 D1 D3 FGND EXTERNAL CROWBAR PROTECTION † SCR D2 RBAT D4 15 RING RING LINE BREAK SW2 ACCESS SW4 RLINE R2 RRING 12 11 LATCH † † TLINE EXTERNAL PROTECTOR MAXIMUM VOLTAGE PRIOR TO SWITCHING TO THE ON STATE SHOULD NOT EXCEED 130V. RLINE EXTERNAL PROTECTOR MAXIMUM VOLTAGE PRIOR TO SWITCHING TO THE ON STATE SHOULD NOT EXCEED 220V. RING 7 CONTROL LOGIC GND VDD 10 9 8 INPUT DGND TSD RGEN RING GENERATOR BATTERY FIGURE 1. APPLICATION CIRCUIT 6 SLIC 1 14 RING TIP 2 3 RRLY + 5 VDC ISL5571A TABLE 9. TRUTH TABLE - ISL5571A LOGIC INPUTS SWITCH CONDITION RING LINE BREAK SWITCH RINGING RETURN SWITCH RING ACCESS SWITCH LATCH INPUT TSD TIP LINE BREAK SWITCH IDLE / TALK 0 0 1 or Floating (Note 11) ON ON OFF OFF POWER RINGING 0 1 1 or Floating (Note 11) OFF OFF ON ON IDLE / TALK LATCHED (Note 12) 1 0 1 or Floating (Note 11) ON ON OFF OFF POWER RINGING LATCHED (Note 12) 1 1 1 or Floating (Note 11) OFF OFF ON ON All OFF X X 0 (Note 13) OFF OFF OFF OFF LOGIC STATE NOTES: 11. Thermal shutdown mechanism is active with TSD floating or equal to 5V. 12. If the LATCH pin is low, the logic state of the device is controlled by the INPUT pin. When the LATCH pin goes high, the current logic state is latched. As long as the LATCH pin is held high, the device will no longer respond to any changes applied to the INPUT control pin. The state of the device will be permanently latched until the LATCH pin is taken low. 13. Setting TSD to a logic low overrides the LATCH and INPUT logic pins and forces all switches to turn OFF. Circuit Operation and Design Information Introduction The ISL5571A was designed to be used in subscriber line card applications. A typical application circuit is shown in Figure 1. Its main purpose is to momentarily disconnect the voice circuit (SLIC and CODEC) and connect an external ring generator to ring the phone. This function has been traditionally done by electromechanical relays. The ISL5571A offers the system designer a solid-state switching solution with distinct advantages over the electromechanical relay. These advantages are as follows: • Lower power consumption (20mW vs. 150mW for the relay) • Smaller size, surface mounted package • Bounce-Free switching • Lower impulse noise, Low EMI • Longer life • Provides current limiting, thermal shutdown, and overvoltage protection for the SLIC and CODEC Their bounce-free operation, long lifetime, small size, and low power consumption make the solid-state access switch the preferred choice over electromechanical relays whenever board area, high reliability, and heat reduction are primary concerns. The ISL5571A was designed to be a drop in replacement for the Lucent ATTL7581AAE LCAS device. The Intersil ISL5571A offers superior rON matching between the line break switches for optimal longitudinal balance, higher temperature operation (enabling continuous operation in 7 short loop, high Ringer Equivalency Number applications) and with 3V TTL logic controlled inputs. Basic Functional Description This section describes the basic operation of the ISL5571A. From the application circuit shown in Figure 1, the ISL5571A consists of four switches, the Line Break switches (SW1, SW2), the Ring Return switch (SW3), and the Ring Access switch (SW4). The Line Break switches (SW1 and SW2) open and close in unison to connect and disconnect the voice / data signal from the phone. The Ring Access switch and the Ring Return switch (SW3 and SW4) open and close in unison, to connect and disconnect the external ring generator to the phone. The ISL5571A has three possible operating states: the Idle / Talk state, the Power Ringing state, and the All OFF state. It also has a built in Logic State Latch. The Logic State Latch enables the user to latch the logic state of the ISL5571A in either the Idle / Talk state or the Power Ringing state. The three control logic pins for the ISL5571A are the INPUT pin, the TSD pin and the LATCH pin. These logic pins are controlled by TTL logic levels (0V - 0.8V for logic low and 2.4V - 5.0V for logic high). The combination of the logic levels applied at these pins determine which of the three logic states the device will be in and whether the Logic State Latch is active. The truth table for the ISL5571A is shown in Table 9. A description of each operating state and the control logic pins follows: ISL5571A Idle / Talk State (LATCH = 0, INPUT = 0, TSD = 1 or Floating) In this state the Line Break switches (SW1 and SW2) are closed (on) and the Ring Return and Ring Access switches (SW3 and SW4) are open (off). The subscriber line circuit is either on-hook or off-hook: the LATCH pin is taken low the device will again be under the control of the INPUT pin and the switches will immediately go to the state specified by the logic level at the INPUT pin. (Note: The TSD pin overrides the LATCH pin and the INPUT pin. When the TSD pin is low the ISL5571A goes to the ALL OFF state regardless of the logic levels applied at the LATCH pin and the INPUT pin.) 1. In the on-hook condition, the SLIC is monitoring the Tip and Ring lines through the Line Break switches for an offhook condition. This is called the Idle state. ISL5571A 2. In the off-hook condition, a telephone conversation between two or more parties is in progress or data is being transferred between modems. This is called the Talk state. The SLIC is providing DC power through the Line Break switches to the telephone handset for modulation. Modulated AC voice signals or data are traveling through the Line Break switches SW1 and SW2. SWITCHES LOGIC CONTROL CIRCUITRY LOGIC STATE LATCH 10 INPUT 8 TSD Power Ringing State (LATCH = 0, INPUT = 1, TSD = 1 or Floating) In this state the Line Break switches (SW1 and SW2) are open (off) and the Ring Return and Ring Access switches (SW3 and SW4) are closed (on). For ring injected ringing as shown in Figure 1, a ring generator is connected to the phone through the Ring Access switch (SW4) and returned to ground through the Ring Return switch (SW3). All OFF State (LATCH = X, INPUT = X, TSD = 0) In this state both the Line Access switches (SW1 and SW2) and the Ring Return and Ring Access switches (SW3 and SW4) are open (off). The ISL5571A will enter the All Off state when the following conditions occur: 11 LATCH FIGURE 2. BLOCK DIAGRAM OF LOGIC CONTROL INPUT Pin The INPUT pin (pin 10) is the main logic input control pin. Reference Table 9 for logic state table. When the LATCH pin is low and the TSD pin is high or floating, you can toggle back and forth between the Idle / Talk state and the Power Ringing state by changing the logic level at the INPUT pin. This is the normal operating mode of the device. NOTE: 1. The TSD pin is used as a control input and is programmed to logic low. The TSD pin overrides all other logic pins. If the TSD pin is low, the device will enter an All OFF state and will no longer respond to logic changes at the INPUT pin. 2. The device has enter thermal shutdown due to a fault condition. (Thermal Shutdown is described in the Auxiliary Functions and Features section below.) 3. If VBAT rises above -10V or disappears. While in the All OFF state, communication and power ringing are inoperable because all the ISL5571A switches are open (off). Logic State Latch (LATCH = 1, TSD = 1 or floating, INPUT = 0 or 1) A Logic State Latch is Integrated into the ISL5571A, see Figure 2. If the LATCH control pin is high and the TSD pin is high or floating, the device will no longer respond to logic level changes at the INPUT pin. The state of the switches will be determined by the logic level of the INPUT pin at the time the LATCH pin transitions from logic low to logic high. The state of the switches at the time of this transition will be permanently held as long as the LATCH pin is high. When 8 If the LATCH pin is high, the INPUT pin is no longer active and the device will no longer respond to logic changes at the INPUT pin. Latch Pin The LATCH pin (pin 11) is the control for the Logic State Latch. Reference Table 9 for logic state table. When the LATCH pin is low, the latch is disabled and the state of the ISL5571A will be determined by the logic level applied at the other logic inputs. When the LATCH pin is high, the latch is active and the logic state of the switches at the time the LATCH pin went high will be latched. As long as the LATCH pin is held high the switches will not respond to logic changes at the INPUT control pin. ISL5571A TSD Pin +I The TSD pin (pin 8) can be used as a logic level input or output. Reference Table 9 for logic state table. The TSD pin overrides all other logic pins. 2/3 rON As an input, if this pin is driven low, either by external logic applied to it or by the internal thermal shutdown circuitry, the ISL5571A device will enter the All OFF state. In the All OFF state all switches of the ISL5571A are open (off). As an output, it is capable of driving a TTL input (2.8V at 200µA). The TSD pin will read +5V when the device is in normal operating mode and 0V when the device is in thermal shutdown. This pin can be monitored on an oscilloscope to determine if the ISL5571A device has enter thermal shutdown. (Thermal Shutdown is described in the Auxiliary Functions and Features section below.) Connecting the TSD pin to 5V will have no effect on the performance of the ISL5571A device and will not disable the thermal shutdown circuitry. CURRENT LIMITING ILIMIT rON -1.5 +1.5 -V +V rON 2/3 rON ILIMIT CURRENT LIMITING -I FIGURE 3. ON STATE V-I GRAPH OF SW1, SW2 AND SW3 Auxiliary Functions and Features +I In addition to the ISL5571A main function of momentarily connecting and disconnecting an external ring generator to ring the phone, the ISL5571A device also provides surge and power-cross protection to the SLIC and CODEC. This fault protection is provided by a combination of currentlimiting circuitry, a thermal shutdown mechanism and an over-voltage clamping circuit. Another feature the device offers is a VBAT fault detection circuit. The following describes each in detail. T1 T2 -V +V T2 Current Limiting The Line Break switches (SW1 and SW2) and the Ring Return switch (SW3) are all current-limited. These switches have a DC current limiting response and a dynamic current limiting response which were built into the device to provide protection during lightning and power-cross faults. Each of these current limiting responses are explained below. DC CURRENT LIMITING RESPONSE The ON state V-I Graph for SW1, SW2, and SW3 is shown in Figure 3. It represents the DC current limiting response of the switches. The graph shows that over a certain range of positive and negative voltages, the current and voltage relationship is linear and behaves according to Ohms law (V = IR). Note: At around ±1.5V an inflection point occurs decreasing the on resistance by 2/3. The on resistance specified in the data sheet is measured in the region prior to the inflection point (between ±1.5V). When current through the switch reaches the current limit of the switch, the current is clamped and held at a constant value. The switch then operates as a constant current source. Increasing the voltage beyond this point will not change the value of the current. 9 T1 T2 > T1 -I FIGURE 4. EFFECT OF TEMPERATURE ON DC CURRENT LIMIT +I 2A 0 TIME 0.5µs FIGURE 5. DYNAMIC CURRENT LIMIT RESPONSE ISL5571A The DC current limiting response has a negative temperature coefficient. As the temperature of the device increases the DC current limit of the switch will decrease. This is illustrated in Figure 4. Figure 4 shows the V-I curves of a switch at two different die temperatures, T1 and T2. In this illustration T2 is greater in temperature than T1. This shows that when a switch is driven into current limit and held there, the current limit will decrease over time as the switch temperature increases. If the power through the switch is great enough, the temperature of the switch will continue to increase until the switch goes into thermal shutdown (Thermal Shutdown is described below). Dynamic Current Limiting Response The DC current limit response described above pertains to DC and AC voltage sources applied across the switches. The dynamic response is the response of the current limit circuit to a fast or high dv/dt pulse. The dynamic response would be seen, for example, during a lightning surge Figure 5 shows the dynamic response that is observed when SW1, SW2 or SW3 is surged with a 1000V at 10/1000µs telecom surge pulse. (Note: This surge test is done with the switch in the on state and with the appropriate external secondary protection in place.) The dynamic current limit of SW1, SW2 or SW3 will limit the current through the switch to less than 2.0A for 0.5µs as shown in Figure 5. Once the switch has turned off, the voltage at the TLine and RLine terminals will increase to a point where the external secondary protection device will trigger and crowbar the voltage at TLine and RLine to a low voltage, protecting the ISL5571A against damage. Since the Line Break switches (SW1, SW2) have this dynamic current limit feature, the internal over-voltage protection clamping circuit of the ISL5571A device will need to only protect the SLIC against a 2.0A ≤0.5µs pulse during a lightning surge. Thermal Shutdown (TSD) The ISL5571A has a built in thermal shutdown protection circuit. The thermal shutdown protection mechanism is invoked if a fault condition causes the junction temperature of the die to exceed about 150oC. Once the thermal limit is exceeded the thermal shutdown circuitry will force the switches into an All OFF state, regardless of the logic inputs. While in thermal shutdown the TSD logic pin (pin 11) will be driven low by the thermal shutdown circuit. (Note: During normal operation the TSD pin is high.) The thermal shutdown mechanism was designed to have a thermal hysteresis of about 12oC. Once in thermal shutdown the device will begin to cool down, because all the switches are off and no current flows. When the temperature of the die cools to about 138oC the ISL5571A will cycle out of thermal shutdown and the switches will close again. If the fault 10 condition is still present, the temperature of the die will again increase and this cycle will be repeated. Over Voltage Protection Clamping Circuit The ISL5571A contains an over-voltage clamping circuit on the SLIC side of the Line Break switches, see Figure 1. This clamping circuit consists of a diode bridge and SCR. During lightning surges and power-cross fault conditions this circuit will clamp the voltage at the TBAT and RBAT terminals of the SLIC to a safe level and will shunt harmful currents to ground away from the SLIC. The clamping circuit is externally connected to ground through the FGND pin (pin 1) of the device. The battery voltage of the SLIC is connected to the clamping circuit through the VBAT pin (pin 16) of the device. The operation of diode bridge and the SCR circuit is described below. DIODE BRIDGE WITH SCR (ISL5571A) During a positive lightning surge or during the positive cycle of a power-cross / induction fault, the voltage at the TBAT and RBAT terminals of the SLIC will be clamped to a diode drop above ground. The fault current will flow harmlessly through diodes D1 and D2 of the diode bridge to ground (see Figure 1). During a negative lightning surge or during the negative cycle of a power-cross / induction fault when the voltage at the TBAT and RBAT terminals reach 2V to 4V more negative than the VBAT voltage, the protection SCR will trigger and turn on. When the SCR turns on and latches, it will crowbar the voltage at the TBAT and RBAT lines to a low-voltage state, approximately 3 diode drops below ground. This lowvoltage on state will cause the current resulting from the over voltage to be safely direct to ground through diodes D3 and D4 of the diode bridge and the SCR (see Figure 1). Once the fault current decrease below the protection SCR holding current (110mA) the SCR will turn off and the SLIC will be able to return to normal operation. VBAT Fault Circuit Protection - Loss of Battery Voltage The ISL5571A device contains a VBAT fault circuit which monitors the SLIC battery voltage (VBAT). When this circuit detects that the VBAT voltage has risen above -10V, it will cause the ISL5571A to enter the All OFF state. All the switches will remain off (open) until the circuit detects that the SLIC battery voltage has dropped below -15V. Design Considerations External Protection Subscriber line card circuits using the ISL5571A require the use of an external protection circuit on the loop side or phone side of the device, see Figure 1. This protection is required to minimize the power stress on the ISL5571A during overvoltage and overcurrent conditions. When the proper external protection circuitry is used in conjunction ISL5571A with the integrated secondary protection, features offered by the ISL5571A, the application circuit will pass the AC powercross and lightning immunity tests of the following regulatory requirements: • GR 1089-CORE Ringing state to the Idle / Talk state. There is a period of time that can be as much as 25ms (1/2 cycle of the 20Hz ring signal) when both SW2 and SW4 will both be on (closed). This occurs because SW4 is an SCR and requires a zero current crossing to turn off. Protection SRC Latch-Up • ITU-T K.20 This section will discuss the issues that must be considered when designing an external protection circuit for use with the ISL5571A. The external protection circuitry should be designed to limit the peak voltages on the TLine and RLine terminals of the ISL5571A. The most potentially stressful condition concerning the ISL5571A is low level power-cross when the ISL5571A switches are closed. Under this condition, the external protection circuitry limits the voltage and corresponding power dissipation until the ISL5571A thermal shutdown circuitry opens the switches. The external protector chosen for the TLine terminal must limit at a maximum of 130V thereby limiting the power stress on the Ring Return switch (SW3). The protector chosen for the RLine terminal must limit at a maximum of 220V thereby limiting the power stress on the Line Break switch (SW2). The 220V break-over voltage of the protector on RLine is large enough to not interfere with the AC ring signal during ringing. Texas Instruments and Teccor Electronics have designed specific parts to protect solid state line card access switches. The following protectors are recommended: Texas Instruments Part Number TISPL758LF3D(TLine and RLine) Teccor Electronics Part Number P1200SC (TLine) and P2000SC (RLine) Refer to the above company’s data sheets for information on their parts and reference designs for protection of solid state line card access switches, see Related Literature section on Page One. Break-Before-Make Operation The ISL5571A device inherently has a Break-before-Make condition between the following switches: a. Between the Line Break switch SW1 and the Ring Return switch SW3 during the transition from the Idle state to the Power Ringing state. b. Between the Line Break switch SW2 and the Ring Access switch SW4 during the transition from the Idle state to the Power Ringing state. Make-Before-Break Operation The ISL5571A device could exhibit a Make-before-Break condition between the Line Break switch SW2 and the Ring Access switch SW4 during the transition from the Power 11 In the Make-before-Break condition, when transiting from the Power Ringing state to the Idle/ Talk state, during the negative cycle of the ring generator it is possible for enough current to flow that the protection SCR will turn on. This will result in shorting the ring generator and the Ring terminal of the SLIC to ground. When either SW2 or SW4 turns off, the Ring terminal of the SLIC will remain shorted to ground unless the output current limit of the SLIC is less than the holding current (110mA) of the protection SCR. The current limit of most SLICs are set well below the 110mA minimum holding current of the ISL5571A protection SCR and therefore should not be a concern. Another method to prevent latch-up of the protection SCR would be to strobe the TSD pin of the ISL5571A. as discussed in Break-Before-Make section. Ring Access Switch Quiescent Current During Ringing The Ring Access switch (SW4) is a silicon control rectifier type switch (SCR). During power ringing, the Ring Access switch will draw a nominal 2mA of current from the ring generator. This current is called IRING QUIESCENT and is equal to: IRING QUIESCENT = IRING GEN - IRING LOAD . System designers need to ensure that this additional current can be provided by the ring generator. Glossary of Acronyms AC = Alternating Current BIMOS = Bipolar Metal-Oxide Semiconductor CO = Central Office CODEC = CODer-DECoder DC = Direct Current DLC = Digital Loop Carrier DAML = Digitally Added Main Line EMI = Electromagnetic Interference ESD = Electrostatic Discharge FITL = Fiber in the Loop HFC = Hybrid Fiber Coax ICs = Integrated Circuits LCAS = Line Card Access Switch PBX = Private Branch Exchange REN = Ring Equivalency Number MOSFET = Metal-Oxide Semiconductor Field-Effect Transistor SCR = Silicon Control Rectifier SLIC = Subscriber Line Interface Circuit SMDs = Surface Mount Devices SOIC = Small Outline Integrated Circuit TSD = Thermal ShutDown TTL = Transistor-Transistor Logic ISL5571A Small Outline Plastic Packages (SOIC) N M16.3 (JEDEC MS-013-AA ISSUE C) INDEX AREA 0.25(0.010) M H B M 16 LEAD WIDE BODY SMALL OUTLINE PLASTIC PACKAGE E INCHES -B- 1 2 SYMBOL 3 L SEATING PLANE -A- h x 45o A D -C- µα e A1 B 0.10(0.004) 0.25(0.010) M C A M B S 1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of Publication Number 95. MILLIMETERS MIN MAX NOTES A 0.0926 0.1043 2.35 2.65 - 0.0040 0.0118 0.10 0.30 - B 0.013 0.0200 0.33 0.51 9 C 0.0091 0.0125 0.23 0.32 - D 0.3977 0.4133 10.10 10.50 3 E 0.2914 0.2992 7.40 7.60 4 0.050 BSC 1.27 BSC - H 0.394 0.419 10.00 10.65 - h 0.010 0.029 0.25 0.75 5 L 0.016 0.050 0.40 1.27 6 8o 0o N NOTES: MAX A1 e C MIN α 16 0o 16 7 8o Rev. 0 12/93 2. Dimensioning and tolerancing per ANSI Y14.5M-1982. 3. Dimension “D” does not include mold flash, protrusions or gate burrs. Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006 inch) per side. 4. Dimension “E” does not include interlead flash or protrusions. Interlead flash and protrusions shall not exceed 0.25mm (0.010 inch) per side. 5. The chamfer on the body is optional. If it is not present, a visual index feature must be located within the crosshatched area. 6. “L” is the length of terminal for soldering to a substrate. 7. “N” is the number of terminal positions. 8. Terminal numbers are shown for reference only. 9. The lead width “B”, as measured 0.36mm (0.014 inch) or greater above the seating plane, shall not exceed a maximum value of 0.61mm (0.024 inch) 10. Controlling dimension: MILLIMETER. Converted inch dimensions are not necessarily exact. All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems. Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries. For information regarding Intersil Corporation and its products, see www.intersil.com 12