Digital isolation system with ADC offset calibration
First Claim
1. An analog-to-digital converter (ADC) offset calibration system in a digital isolation system having a powered circuit on a first side of a isolation barrier and an isolated circuit on a second side of the barrier, wherein digital signals are transmitted across the isolation barrier, and wherein an ADC requiring calibration is located on the second side of the isolation barrier, the ADC offset calibration system comprising:
- a digital integrator connected to receive an output signal from the ADC and to provide an integrated offset calibration signal;
a data register connected to receive and hold the integrated offset calibration signal, the data register outputting a held offset calibration signal;
a digital to analog converter having an input connected to receive the held offset calibration signal and having an output providing an analog offset calibration signal;
wherein the analog offset calibration signal is connected to an input of the ADC requiring calibration.
1 Assignment
0 Petitions
Accused Products
Abstract
A digital capacitive isolation barrier system is provided that is suitable for use in a telephone or modem where the locally powered circuits must be effectively isolated from the public telephone system, while permitting data transfer across the barrier. In particular, an automatic ADC offset calibration system is provided for determining the magnitude of the ADC offset signal required in the system during a calibration operation, and for providing the ADC offset signal during normal operation of the isolation barrier system. Fixed bias signals are also provided for the ADC and for a DAC in the system. In a preferred embodiment, the ADC is located on the isolated side of the isolation barrier, while the integrator and register that determine and hold the offset signal are located on the powered side of the isolation barrier.
57 Citations
20 Claims
-
1. An analog-to-digital converter (ADC) offset calibration system in a digital isolation system having a powered circuit on a first side of a isolation barrier and an isolated circuit on a second side of the barrier, wherein digital signals are transmitted across the isolation barrier, and wherein an ADC requiring calibration is located on the second side of the isolation barrier, the ADC offset calibration system comprising:
-
a digital integrator connected to receive an output signal from the ADC and to provide an integrated offset calibration signal; a data register connected to receive and hold the integrated offset calibration signal, the data register outputting a held offset calibration signal; a digital to analog converter having an input connected to receive the held offset calibration signal and having an output providing an analog offset calibration signal; wherein the analog offset calibration signal is connected to an input of the ADC requiring calibration. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A method of performing analog-to-digital converter (ADC) offset calibration in a digital isolation system, comprising:
-
maintaining a data input signal into an ADC being calibrated at a level of zero; integrating an output signal from the ADC being calibrated to provide an integrated offset calibration signal; holding the integrated offset calibration signal in a data register; converting the integrated offset calibration signal from a digital signal to an analog offset calibration signal; adding the analog offset calibration signal to said data input signal; and latching the integrated offset calibration signal in the data register when the output signal from the ADC becomes zero. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
-
Specification