Datenblatt-Suchmaschine für elektronische Bauteile |
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ISL5586FCM Datenblatt(PDF) 8 Page - Intersil Corporation |
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ISL5586FCM Datenblatt(HTML) 8 Page - Intersil Corporation |
8 / 20 page 4-8 To allow for proper ring trip operation, the transient current limit setting should be set at least 25% higher than the peak ring trip current setting. Setting the transient current 25% higher should account for programming tolerances of both the ring trip threshold and the transient current limit. If loop current is larger than ring trip current (low REN applications) then the transient current limit should be set at least 35% higher than the loop current setting. The slightly higher offset accounts for the slope of the loop current limit function. Attention to detail should be exercised when programming the transient current limit setting. If ring trip detect does not occur while ringing, then re-examine the transient current limit and ring trip threshold settings. Low Power Standby Mode Overview The low power standby mode (LPS, 000) should be used in conjunction with the high battery during idle line conditions. The SLIC is designed to operate from the high battery during this mode so MTU compliance can be met. Most of the internal circuitry is powered down, resulting in low power dissipation. If MTU compliance is not required during idle line conditions, the device may be operated from the low battery which will decrease the standby power dissipation. 2-Wire Interface In the LPS mode, the 2-wire interface is maintained with internal switches, resistors, and voltage references. The Tip and Ring amplifiers are turned off to conserve power. The device will provide MTU compliance, loop current, and loop supervision. Figure 2 represents the internal circuitry providing the 2-wire interface when in this mode of operation. MTU Compliance Maintenance Termination Unit or MTU compliance places DC voltage requirements on the 2-wire terminals during idle line conditions. The minimum idle voltage for compliance is 42.75V. The high side of the MTU range is 56V. The voltage is expressed as the difference between Tip and Ring. The Tip voltage is held near ground through a 600 Ω resistor and switch. The Ring voltage is nominally limited to -49V by the MTU reference. A switch and 600 Ω resistor connect the MTU reference to the Ring terminal. When the high battery voltage exceeds the MTU reference of -49V, the Ring terminal will be clamped by the internal reference. The same Ring relationships apply when operating from the low battery. For operating battery voltages (VBH) less than or equal to the internal MTU reference, the Ring voltage will be approximately 4.5 volts more positive than VBH. Loop Current In the LPS mode, the device is capable of providing DC current to a load through a path of resistors and switches. The current available for switch hook detect is a function of the off hook loop resistance (RLOOP). This includes the off hook phone resistance and copper loop resistance. The current available during LPS is given by Equation 15. Internal current limiting of the standby switches will limit the maximum current to approximately 23mA. The longitudinal current capability is guaranteed to be greater than or equal to 10mARMS per pin. When longitudinal currents exceed this level, false off hook detection may occur. The reduction in longitudinal current capability with respect to the Forward Active mode is a result of turning off the Tip and Ring amplifiers. On Hook Power Dissipation The on hook power dissipation of the SLIC in the LPS mode is determined by the operating voltages and quiescent currents and is calculated below. TABLE 1. DEVICE INTERFACES DURING LPS INTERFACE ON OFF NOTES Receive - x AC transmission, impedance matching and ringing are disabled during this mode. Ringing - x Transmit - x 2-Wire x - Amplifiers disabled. Loop Detect x - Switch hook. FIGURE 3. LPS 2-WIRE INTERFACE CIRCUIT DIAGRAM TIP AMP RING AMP TIP RING MTU REF GND 600 Ω 600 Ω I LOOP 1 – 49 – () – () 600 600 R LOOP ++ () ⁄ = (EQ. 15) P LPS V BH I BH Q × V BL I BL Q × V CC I CC Q × ++ = (EQ. 16) ISL5586 |
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Ähnliche Beschreibung - ISL5586FCM |
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