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L9311 Fiches technique(PDF) 34 Page - Agere Systems |
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L9311 Fiches technique(HTML) 34 Page - Agere Systems |
34 / 50 page Data Sheet July 2001 Ringing Relay, and GR-909 Test Access L9311 Full-Feature SLIC with High Longitudinal Balance, 34 Agere Systems Inc. Supervision (continued) Ring Trip Ring trip is set by the value of RS1. The ring trip threshold at the ring trip inputs is ±2.5 V minimum, ±3.5 V maximum. A resistor value of 400 Ω, as shown in Figure 4, will set the ring trip current threshold to ±7.5 mA typical. Ring trip is asserted upon entering the ringing mode until the second zero crossing of ringing. This is either a positive-going zero crossing (between –40 V and –30 V at –50 V VBAT) or a negative-going zero crossing (between –10 V and –20 V at –50 V VBAT). The different threshold for positive-going and negative-going zero crossings is the result of hysteresis of approximately 20 V. The act of turning on the switch may or may not produce a ringing zero crossing, therefore, there may be a delay of up to almost one cycle of ringing or 50 ms until NSTAT is high. Ring trip will not be asserted unless the ring trip thresh- old is exceeded for two zero crossings. This is either a positive-going zero crossing (between –40 V and –30 V at –50 V VBAT) or a negative-going zero crossing (between –10 V and –20 V at –50 V VBAT). The different threshold for positive-going and negative-going zero crossings is the result of hysteresis of approximately 20 V. Note that since the ringing voltage is monitored at RSW, one zero crossing can occur at switch turn-on depending on initial conditions. Ring trip is asserted immediately if the ring trip input is 15 V ± 3 V. Ring Ground Detector In ground start applications, a common-mode current detector is used to indicate a ring ground has occurred or an off-hook has occurred. The detection threshold is set by connecting a resistor from ICM to ground. 2350/RICM (k Ω) = ITH (mA) Additionally, a filter capacitor across RICM will set the time constant of the detector. No hysteresis is associ- ated with this detector. Switching Behavior The solid-state ring relay in the L9311 device is able to provide either make-before-break or break-before- make timing with respect to switching into and out of the ring mode. If switching is done directly into and out of the ring mode, the design of the L9311 will give make-before-break switching with respect to both the ring and tip side switches. To achieve break-before- make switching, the user should via software control enter an intermediate all-off mode when switching into and out of the ring mode. The all-off state should be held a minimum of 8 ms. Make-Before-Break Operation The break switches are constructed from DMOS tran- sistors. The tip side ring return is also a DMOS transis- tor. Because the on resistance of the break switches is less than the tip side ring return switch, the break switches are physically bigger. This implies a larger gate to source capacitance, with inherently slower switching speeds since it will take longer to charge or discharge the gate to source capacitance of the break switches (to change the state of the switch). The ring access switch is a pnpn type device. The pnpn device has inherently faster switching speeds than any of the DMOS type switches. Going from the active to ring mode, the smaller tip side ring return switch and the pnpn ring access switch will change states before the larger break switches. Thus, the ring contacts are made before the line break switches are broken: make-before-break operation. Going from the ring mode to active or scan, the natural tendency is for the smaller tip side ring return DMOS to break or open, before the larger DMOS can turn on. This would not be make-before-break operation on the tip side. Thus, circuitry is added to speed up charging of the tip break switch, to speed up the turn on of that switch to give make-before-break operation on the tip side. On the ring side, going from the ring mode to the active or scan mode, the pnpn will not turn off until the ring current drops below the hold current of the pnpn device (which is typically 500 µA); this is effectively zero cur- rent for zero current turn off. This can take up to one- half cycle of ringing to occur. With this inherent delay in switching by the pnpn ring access switch, the break switches will make contact before the ring access switch breaks contact; so again, make-before-break switching is achieved. |
Numéro de pièce similaire - L9311 |
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Description similaire - L9311 |
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