Digitally self-calibrating current-mode D/A converter
First Claim
Patent Images
1. An apparatus including a current cell for a digitally self-calibrating current-mode digital-to- analog converter, comprising:
- a reference signal generator configured to provide a reference signal;
a signal output terminal;
a signal comparison terminal;
a reference terminal;
a first conversion switch coupled between said signal generator and said signal output terminal;
a second conversion switch coupled between said signal generator and said reference terminal; and
a calibration switch coupled between said signal generator and said signal comparison terminal;
wherein said first conversion switch, said second conversion switch and said calibration switch selectively couple said signal generator to at least one of said signal output terminal, said signal comparison terminal and said reference terminal, and in accordance thereto, provide an output signal.
1 Assignment
0 Petitions
Accused Products
Abstract
Digital self-calibration of digital-to-digital converters includes an approach to correct for the arbitrary errors in the analog section provided that there are sufficient redundancy in the architecture. The calibration procedure is performed off-line (upon power-up or user request). The digital correction technique avoids the need of a very accurate current mirror or an extra digital-to-analog converter as a standard transfer device.
104 Citations
23 Claims
-
1. An apparatus including a current cell for a digitally self-calibrating current-mode digital-to- analog converter, comprising:
-
a reference signal generator configured to provide a reference signal; a signal output terminal; a signal comparison terminal; a reference terminal; a first conversion switch coupled between said signal generator and said signal output terminal; a second conversion switch coupled between said signal generator and said reference terminal; and a calibration switch coupled between said signal generator and said signal comparison terminal; wherein said first conversion switch, said second conversion switch and said calibration switch selectively couple said signal generator to at least one of said signal output terminal, said signal comparison terminal and said reference terminal, and in accordance thereto, provide an output signal. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. An apparatus including a digitally self-calibrating current mode digital-to-analog converter, comprising:
-
an encoder configured to receive an input signal and in accordance thereto generate an encoded signal; an output terminal; an output switch coupled to said output terminal; a calibration switch; a reference signal switch coupled to said calibration switch and said output switch; a reference signal generator coupled to said reference signal switch configured to generate a reference signal; a calibration engine coupled to said encoder configured to generate a plurality of correction coefficients; a plurality of current cells each coupled to said calibration engine, each of said current cells configured to receive said plurality of correction coefficients and in accordance thereto, generate a first and second current cell signals; a comparator having a first input terminal, a second input terminal and a comparator output terminal, said first input terminal coupled to said calibration switch, said second input terminal coupled to said plurality of current cells, and said comparator output terminal coupled to said calibration engine, said comparator configured to receive said first and second current cell signals and to selectively receive said reference signal and in accordance thereto provide a comparator output signal to said calibration engine; and a controller coupled to said encoder, said reference signal switch, said calibration switch, said output switch and said calibration engine, configured to generate one or more control signals; wherein said comparator receives said reference signal in accordance with the switching of said calibration switch and said reference signal switch, and in accordance with generate a compared signal; and
furtherwherein said output switch selectively provides an output signal to said output terminal in accordance with said one or more control signals. - View Dependent Claims (8, 9, 10)
-
-
11. An apparatus including a current mode comparator for a digitally self-calibrating current mode digital-to-analog converter, comprising:
-
a first input terminal configured to receive a first input signal; a second input terminal configured to receive a second input signal; an output terminal configured to provide an output signal, said output terminal coupled to said second input terminal; a reference terminal; a first transistor having a first terminal, a second terminal and a third terminal, said third terminal coupled to said reference terminal; a second transistor having a first terminal, a second terminal and a third terminal, said third terminal coupled to said reference terminal and said second transistor second terminal coupled to said first transistor second terminal; and a plurality of switches coupled between said first input terminal, said second input terminal and said first and second transistor first terminals; wherein said plurality of switches selectively couple said first and second input terminals to said first and second transistor first terminals and in accordance thereto providing a comparator output signal to said output terminal such that the current density of said first and second transistors are substantially constant. - View Dependent Claims (12, 13, 14, 15, 16, 17)
-
-
18. A method of digitally self-calibrating a current mode digital-to-analog converter including a plurality of current cells, said method comprising the steps of:
-
initializing a plurality of memory locations with an initialization factor; calibrating each of a plurality of current cells with a first calibration factor and in accordance thereto generating a plurality of correction coefficients, each of said correction coefficients corresponding to one of said current cells; calibrating said correction coefficients in accordance with a second calibration factor and storing each of said calibrated correction coefficients in said respective memory locations; and normalizing said plurality of calibrated correction coefficients in accordance with a normalization factor and in accordance thereto generating an output signal. - View Dependent Claims (19, 20)
-
-
21. A method of performing digital correction for a current mode digital-to-analog converter including N current cells where N is an integer, said method comprising the steps of:
-
for each ith current cell, where i=1 to N; receiving an input digital signal; comparing said input digital signal to a corresponding ith correction coefficient; if said input digital signal is larger than said corresponding ith correction coefficient, generating a first output digital signal and subtracting said ith correction coefficient from said input digital signal to generate an input digital signal for (i+1)th current cell; and if said input digital signal is not larger than said corresponding ith correction coefficient, generating a second output digital signal. - View Dependent Claims (22, 23)
-
Specification