CPC7591BATR

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1. Description

The CPC7591BATR is a member of IXYS Integrated Circuits Division’s next generation Line Card Access Switch (LCAS) family. This monolithic 4-pole solid state switch is available in a 16-pin SOIC package. It provides the necessary functions to replace the 2-Form-C electromechanical ringing relay and it’s associated snubber circuitry on traditional analog line cards or contemporary integrated voice and data (IVD) line cards found in Central Office (CO), Access, and PBX equipment. Because this device contains solid state switches for tip and ring line break and for ringing injection/return, it requires only a +5 V supply for operation and TTL logic-level inputs for control. The CPC7591 provides stable start-up conditioning during system power up and for hot plug insertion applications. Once active, the inputs respond to traditional TTL logic levels, enabling the CPC7591 to be used with 3.3V-only logic. For negative transient voltage protection the CPC7591BA version includes SCRs to provide voltage fold-back protection for the SLIC and subsequent circuitry, while the CPC7591BB version utilizes clamping diodes to the VBAT pin. For positive transient voltage protection all versions provide clamping diodes to the FGND pin.

2. Features

    1. TTL Logic Level Inputs for 3.3V Logic Interfaces

    2. Smart Logic for Power Up / Hot Plug State Control

    3. Improved Switch dV/dt Immunity of 500 V/s

    4. Monolithic IC Reliability

    5. Low, Matched RON

    6. Eliminates the Need for Zero-Cross Switching

    7. Flexible Switch Timing for Transition from Ringing Mode to Idle/Talk Mode.

    8. Clean, Bounce-Free Switching

    9. Tertiary Protection Consisting of Integrated Current Limiting, Voltage Clamping, and Thermal Shutdown for SLIC Protection

  10. 5V Operation with Power Consumption < 10 mW

  11. Intelligent Battery Monitor

  12. Latched Logic-Level Inputs, no External Drive Circuitry

  13. Small 16-pin SOIC

3. Applications

    1. VoIP Gateways

    2. Central office (CO)

    3. Digital Loop Carrier (DLC)

    4. PBX Systems

    5. Digitally Added Main Line (DAML)

    6. Hybrid Fiber Coax (HFC)

    7. Fiber in the Loop (FITL)

    8. Pair Gain System

    9. Channel Banks

4. Pin configuration

5. Pin description

6. Function Description

    1. Introduction

        CPC7591 has three states:

        - Talk. The disconnection switches SW1 and SW2 are closed, and the ringing switches SW3 and SW4 are opened.

        - Ringtones. The ringing switches SW3 and SW4 are closed, and the disconnection switches SW1 and SW2 are open.

        - Close all. All switches are turned on.

CPC7591 provides simple TTL level logic input control for switching from the ringing state to the call state by opening before closing and opening before breaking. The solid-state switch structure means that when there is no pulse ringing, a noise rhythm or ringing trip occurs when switching, and no external zero-crossing switch circuit is required. The state control is input through TTL logic level, so no additional driving circuit is necessary. The linear disconnect switches SW1 and SW2 have extremely low RON and excellent matching characteristics. Ringing switch, SW4, It has a minimum open-circuit contact breakdown voltage of 465 V at +25C, which is high enough and has adequate protection to prevent breakdown fault conditions during transients. Integrated into CPC7591 is an overvoltage Clamping circuit, active current limit and thermal shutdown mechanism to provide protection for SLIC in case of failure. The positive and negative lightning surge current is reduced by the current limiting circuit and the dangerous potential is transferred through the protection diode bridge away from the SLIC or the optional integrated protection SCR. Power crossover The current limit also reduces the potential and thermal shutdown circuit. To protect the CPC7591 from overvoltage faults, a secondary protector is required. The secondary protector must be limited to The TLINE and RLINE terminals are lower than the maximum breakdown voltage of the switch. To minimize the stress on the solid contacts, the use of a foldback or crowbar type secondary protector is strongly recommended. By appropriately selecting the secondary protector, the line card using CPC7591 will meet all relevant ITU, LSSGR, TIA/EIA and IEC protection requirements. CPC7591 adopts +5 V single power supply. This allows the device to have extremely low idle and almost any range of active power consumption battery voltage. The battery voltage CPC7591 used has dual functions. Protection purpose It is used as a fault condition current source for the internal integrated protection circuit.

    2. Under Voltage Switch Lock Out Circuitry

Smart logic in the CPC7591 now provides for switch state control during both power up and power loss transitions. An internal detector is used to evaluate the VDD supply to determine when to de-assert the under voltage switch lock out circuitry with a rising VDD and when to assert the under voltage switch lock out circuitry with a falling VDD. Any time unsatisfactory low VDD conditions exist, the lock out circuit overrides user switch control by blocking the information at the external input pins and conditioning internal switch commands to the all-off state. Upon restoration of VDD, the switches will remain in the all-off state until the LATCH input is pulled low. The rising VDD switch lock-out release threshold is internally set to ensure all internal logic is properly biased and functional before accepting external switch commands from the inputs to control the switch states. For a falling VDD event, the lock-out threshold is set to assure proper logic and switch behavior up to the moment the switches are forced off and external inputs are suppressed.  To facilitate hot plug insertion and system power up state control, the LATCH pin has an integrated weak pull up resistor to the VDD power rail that will hold a non-driven LATCH pin at a logic high state. This enables board designers to use the CPC7591 with FPGAs and other devices that provide high impedance outputs during power up and logic configuration. The weak pull up allows a fan out of up to 32 when the system’s LATCH control driver has a logic low minimum sink capability of 4mA.

    3. Switch Logic

The CPC7591 uses smart logic to monitor the VDD supply. Any time the VDD is below an internally set threshold, the smart logic places the control logic to the all-off state. An internal pullup on the LATCH pin locks the CPC7591 in the all-off state following start-up until the LATCH pin is pulled down to a logic low. Prior to the assertion of a logic low at the LATCH pin, the switch control inputs must be properly conditioned. 

    4. Data Latch

The CPC7591 has an integrated transparent data latch. The latch enable operation is controlled by TTL logic input levels at the LATCH pin. Data input to the latch is via the input pin INRINGING, while the output of the data latch are internal nodes used for state control. When the LATCH enable control pin is at logic 0 the data latch is transparent and the INRINGING input data control signal flows directly through the data latch to the state control circuitry. A change in INRINGING input will be reflected by a change in switch state. Whenever the LATCH enable control pin is at logic 1, the data latch is active and data is locked. Subsequent INRINGING input changes will not result in a change to the control logic or affect the existing switch state. The switches will remain in the state they were in when the LATCH pin changes from logic 0 to logic 1 and will not respond to changes in input as long as the LATCH is at logic 1. However, neither the TSD input nor the TSD output control functions are affected by the latch function. Since internal thermal shutdown control and external “All-off” control is not affected by the state of the LATCH enable input, TSD will override state control.

    5. Power Supplies

Both a +5 V supply and battery voltage are connected to the CPC7591. Switch state control is powered exclusively by the +5 V supply. As a result, the CPC7591 exhibits extremely low power consumption during active and idle states. Although battery power is not used for switch control, it is required to supply trigger current for the integrated internal protection circuitry SCR during fault conditions. This integrated SCR is designed to activate whenever the voltage at TBAT or RBAT drops 2 to 4 V below the applied voltage on the VBAT pin. Because the battery supply at this pin is required to source trigger current during negative overvoltage fault conditions at tip and ring, it is important that the net supplying this current be a low impedance path for high speed transients such as lightning. This will permit trigger currents to flow enabling the SCR to activate and thereby prevent a fault induced negative overvoltage event at the TBAT or RBAT nodes.