US 6,445,330 B1 · Capacitively coupled references for isolated analog-to-digital converter systems

Abstract

The present invention provides an alternative to Prior Art isolation techniques by providing a capacitively coupled reference voltage and a capacitively coupled gain calibration. The isolation technique of the present invention is based upon the idea of a near unity gain capacitive divider. If the load or parasitic capacitance is Cload and the isolation capacitance is Ciso, then the gain between input and output can be calculated as Vout/Vin=(Ciso)/(Ciso+Cload), which will be nearly unity (i.e., 1) when Ciso>>Cload. In addition, if Ciso>>Cload, the gain will also be largely insensitive to variations in Ciso and Cload. For example, if Cin is 100 ppm of Ciso, then a 10% variation in Ciso or Cload results in only a 10 ppm variation in the voltage gain.

Claims14

Dependent claims

An isolated analog-to-digital converter system comprising:

at least one analog-to-digital converter subsystem including an analog-to-digital converter for converting an analog signal to a digital data stream, the at least one analog-to-digital converter subsystem having a load capacitance defined as Cload;
a reference voltage subsystem for providing at least one reference voltage signal for the analog-to-digital converter;
and
an isolation subsystem for electrically isolating the at least one analog-to-digital converter subsystem from the reference voltage subsystem, the isolation subsystem comprising:
a capacitive divider having an isolation capacitance Ciso, wherein gain between input and output is calculated as Vout/Vin=(Ciso)/(Ciso+Cload).

2 more elements

A method for isolating an analog-to-digital converter comprising the steps of:

in at least one analog-to-digital converter subsystem including an analog-to-digital converter, converting an analog signal to a digital data stream, the at least one analog-to-digital converter subsystem having a load capacitance defined as Cload,
in a reference voltage subsystem, providing at least one reference voltage signal for the analog-to-digital converter, and
in an isolation subsystem, electrically isolating the at least one analog-to-digital converter subsystem from the reference voltage subsystem, said step of electrically isolating further comprising the step of:
isolating the reference voltage subsystem from the at least one analog-to-digital converter subsystem using a capacitive divider having an isolation capacitance Ciso, wherein gain between input and output is calculated as Vout/Vin=(Ciso)/(Ciso+Cload).

1 more element

Dependencies are inferred from the claim text.

Capacitively coupled references for isolated analog-to-digital converter systems

Life of this patent

Capacitively coupled references for isolated analog-to-digital converter systems

Life of this patent

Abstract

Claims14