LE75181A PRODUCT PROFILE - Zarlink Semiconductor - (Version JPG) - Page n° 9 - PDF Catalogue | Technical Documentation

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Packet switch, Demodulator, Transceiver, Frequency divider, Network transceiver

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Le75181

Data Sheet

Table 5. Make-Before-Break Operation


INPUT	TSD	State	Timing	Break Switches 1 & 2	Ring Return Switch 3	Ring Access Switch 4
1	1/Float	Power Ringing	—	Open	Closed	Closed
0	1/Float	Make- before- break	SW4 waiting for next zero current crossing to turn off, maximum time—one-half of ringing. In this transition state, current that is limited to the dc break switch current-limit value will be sourced from the ring node of the SLIC.	Closed	Open	Closed
0	1/Float	Idle/Talk	Zero cross current has occurred.	Closed	Open	Open

Table 6. Break-Before-Make Operation


INPUT	TSD	State	Timing	Break Switches 1 & 2	Ring Return Switch 3	Ring Access Switch 4
1	1/Float	Power Ringing	—	Open	Closed	Closed
1	0	All Off	Hold this state for <25 ms. SW4 waiting for zero current to turn off.	Open	Open	Closed
0	0	All Off	Zero current has occurred and SW4 has opened. Transition on INPUT should occur during 25 ms hold.	Open	Open	Open
0	1/Float	Idle/Talk	Release break switch pair.	Closed	Open	Open

POWER SUPPLIES

Though both the 5-V and battery supplies are brought onto the Le75181 device, only the 5-V supply is required for switch operation; that is, state control is powered exclusively off of the 5-V supply. Because of this, the Le75181 device offers extremely low power dissipation, both in the Idle and Active states.

The battery voltage is not used for switch state control, but rather as a reference voltage by the integrated secondary protection circuit. When the voltage at TBAT or RBAT drops 2 V to 4 V below the battery, the integrated SCR will trigger, thus preventing fault-induced overvoltage situations at the TBAT/RBAT nodes.

LOSS OF BATTERY VOLTAGE

As an additional protection feature, the Le75181 device monitors the battery voltage. Upon loss of battery voltage, the Le75181 will automatically enter an all OFF state and remain in that state until the battery voltage is restored. The Le75181 is designed so that the device will enter the all OFF state if the battery rises above approximately -10 V and will remain off until the battery drops below approximately -15 V.

Monitoring the battery for the automatic shutdown feature will draw a small current from the battery, typically 4 uA. This will add slightly to the overall power dissipation of the device.

IMPULSE NOISE

Using the Le75181 will minimize and possibly eliminate the contribution to the overall system impulse noise that is associated with ringing access switches. Because of this characteristics of the Le75181, it may not be necessary to incorporate a zero cross switching scheme. This ultimately depends upon the characteristics of the individual system and is best evaluated at the board level.

Zarlink Semiconductor Inc.

LE75181A PRODUCT PROFILE - Zarlink Semiconductor - #9

Packet switch, Demodulator, Transceiver, Frequency divider, Network transceiver