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L9215A Datasheet(PDF) 5 Page - Agere Systems |
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L9215A Datasheet(HTML) 5 Page - Agere Systems |
5 / 50 page Data Sheet September 2001 Short-Loop Sine Wave Ringing SLIC L9215A/G Agere Systems Inc. 5 Description (continued) Forward and reverse battery active modes are used for off-hook conditions. Since this device is designed for short-loop applications, the lower-voltage VBAT2 is applied during the forward and reverse active states. Battery reversal is quiet, without breaking the ac path. Rate of battery reversal may be ramped to control switching time. The magnitude of the overhead voltage in the forward and reverse active modes has a typical default value of 6.0 V, allowing for an undistorted signal of 3.14 dBm into 900 Ω. This overhead can be increased to accom- modate higher signal levels and/or PPM. The ring trip detector is turned off during active modes to conserve power. Because on-hook transmission is not allowed in the scan mode, an on-hook transmission mode is defined. This mode is functionally similar to the active mode, except the tip ring voltage is derived from the higher VBAT1 rather than VBAT2. In the on-hook transmission modes with a primary bat- tery whose magnitude is greater than a nominal 51 V, the magnitude of the tip-to-ground and ring-to- ground voltage is clamped at less than 56.5 V. To minimize on-hook power, a low-power scan mode is available. In this mode, all functions except off-hook supervision are turned off to conserve power. On-hook transmission is not allowed in the scan mode. In the scan mode with a primary battery whose magni- tude is greater than a nominal 51 V, the magnitude of the tip-to-ground and ring-to-ground voltage is clamped at less than 56.5 V. A forward disconnect mode is provided, where all cir- cuits are turned off and power is denied to the loop. The device offers a ring mode, in which a power ring signal is provided to the tip/ring pair. During the ring mode, a user-supplied, low-voltage ring signal (ac cou- pled) is input to the device’s RINGIN input. This signal is amplified to produce the power ring signal. This signal may be a sine wave or filtered square wave to produce a sine wave on trapezoidal output. Ring trip detector and common-mode current detector are active during the ring mode. This feature eliminates the need for a separate external ring relay, associated external circuitry, and a bulk ring- ing generator. See the Applications section of this data sheet for more information. PPM is injected at the PPMIN pin (ac coupled). This is a high-impedance input that controls the PPM differential voltage on tip and ring. The PPM signal may be present at this pin at all times; however, PPM will only be transmitted to tip and ring during a PPM active mode. There are forward and reverse active, and for- ward and reverse on-hook transmission modes with PPM active. No PPM shaping is done by the device. It is assumed that a shaped PPM input is presented to PPMIN. The maximum allowed PPM current at the 200 Ω ac meter pulse load to avoid saturation of the device’s internal AAC amplifier is 3 mArms. This signal level is sufficient to provide a minimum 200 mVrms to the 200 Ω PPM load under maximum specified dc loop conditions. Above 3 mArms PPM current, external meter pulse rejection may be required. See the Appli- cations section of this data sheet for more information if on-hook transmission of PPM is required. Sufficient overhead to accommodate on-hook transmission must be programmed by the user at the OVH input. Both the ring trip and loop closure supervision func- tions are included. The loop closure has a fixed typical 10.5 mA on- to off-hook threshold in the active mode and a fixed 11.5 mA on- to off-hook threshold from the scan mode. In either case, there is a 2 mA hysteresis. The ring trip detector requires only a single-pole filter at the input, minimizing external components. The ring trip threshold at a given battery voltage is fixed. Typical ring trip threshold is 42.5 mA for a –75 V VBAT1. |
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