VOICE CONTROL PROCESSOR LE79252 PRODUCT PREVIEW Features The voltage sense is connected before the test-out relay such that, the impedance generation is present during selftest performed with the loop disconnected The test-out relay is used to disconnect the loop during self-testing, calibration, or to measure sensing offsets The PTCs are inside the impedance feedback loop and don't degrade the longitudinal balance The test load resistor is used for self-testing and to perform limited calibration Foreign Voltage Testing Voltage range at the tip and ring port is normally VBH to VBP but extends to ±400 V when the PTCs are activated Measurement offsets can be calibrated by using the testout relay to disconnect the loop Foreign Current Testing Current range is ±60 mA total common-mode current and ±80 mA differential and common mode current per individual lead Voltage range at the tip and ring port is VBH to VBP, minus the saturation voltage at peak common-mode current The current sensing offset can be calibrated out by operating the test-out relay 3-Element Resistance Testing Current range is ±60 mA total common-mode current and ±80 mA differential and common mode current per individual lead Voltage range at the tip and ring port is VBH to VBP, minus the saturation voltage at peak common-mode current The fixed part of the current sensing offset is cancelled in the test procedure by the two point measurement The variable part of the current sensing offset can be calibrated out by operating the test-out relay Fuse Test The fuse test can be done by executing a 3-element capacitance test in high gain mode with and without the test-out relay activated Loop Resistance Test The voltage sensing offset and the feed current offset are cancelled out by doing a positive and negative polarity measurement at each current level Le79252 SLIC with Internal Ringing Test-Out Bus (optional) SA Fuse (optional) AD TLD VBP VBH (optional) Le79252 SLIC Device PTC or Resistor Disconnect Relay Secondary Protection PTC or Resistor BD RD1 TIP EMR Disconnect Relay EMR SB RING Fuse (optional) Test-Out Bus (optional) Test-Out Relay Information relating to products and services furnished herein by Zarlink Semiconductor Inc. or its subsidiaries is believed to be reliable. The products, their specifications, services and other information appearing in this publication are subject to change by Zarlink without notice. ZARLINK, ZL, and the Zarlink logo are trademarks of Zarlink Semiconductor Inc. © 2010, Zarlink Semiconductor Inc. All Rights Reserved. Publication Number 10ZS232 www.ZARLINK.com