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ADAPTIVE DC BIAS COMPENSATION FOR A/D CONVERTERS

IP.com Disclosure Number: IPCOM000005812D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2001-Nov-08
Document File: 1 page(s) / 55K

Publishing Venue

Motorola

Related People

Kha Le: AUTHOR [+4]

Abstract

In telecommunications applications, it is often necessary to transmit very low frequency information for sub audible signaling and data which requires DC coupling of circuit stages or large coupling capacitors, The response time to DC transient pulses should be kept at a minimum to allow recovery of the system after turn on of pulsed systems such as battery savers where the power supply line is strobed. To allow for transmission of sub audible information and fast recovery time for telecommunications systems using A/D conversion an adaptive system has been developed shown in figure 1 that reads the DC level of the input signal (without modula- tion) and stores that level digitally. Any DC level change caused by make tolerance or temperature change is nulled out.

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MOTOROLA Technical Developments Volume 9 August 1989

ADAPTIVE DC BIAS COMPENSATION FOR A/D CONVERTERS

by Kha Le, King Lee, Fred Martin, 8 John Wetters

   In telecommunications applications, it is often necessary to transmit very low frequency information for sub audible signaling and data which requires DC coupling of circuit stages or large coupling capacitors, The response time to DC transient pulses should be kept at a minimum to allow recovery of the system after turn on of pulsed systems such as battery savers where the power supply line is strobed. To allow for transmission of sub audible information and fast recovery time for telecommunications systems using A/D conversion an adaptive system has been developed shown in figure 1 that reads the DC level of the input signal (without modula- tion) and stores that level digitally. Any DC level change caused by make tolerance or temperature change is nulled out.

   As shown in figure 1, inputs to the circuit are a signal input, Clock and power up signal, that comes from an external source such as a microprocessor controller. The AID converts the analog information of the input signal to a series of digital words that is divided into clock periods from the clock input. After a "power up" signal is received by the circuit, the enable trigger circuit stores n bits of ouput from the a/d that is processed from the signal input port without any information transmission (no modulation, just DC level from the preceding st...