US 9,214,950 B1Granted

Apparatus and method for temperature compensated gain and mismatch trim in subranging quantizers and analog to digital converters

AssigneeLockheed Martin Corporation

InventorsBrandon R. Davis, Toshi Omori, Lloyd F. Linder, Victoria T. Pereira

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Abstract

A flash analog to digital converter (ADC) provides a temperature compensated trim current by applying a first temperature compensated reference current across a replica resistor ladder. The reference current is mirrored to a trim digital to analog converter, which outputs a fractional portion of the temperature compensated reference current. The proportional trim current is then fed back to the reference current to provide a trimmed temperature compensated reference current. The trimmed reference current is mirrored across the output resistor ladder providing a trimmed current in which the trim varies along with temperature changes due to the trim current being a proportion of the temperature compensated reference current. A proportional trim current which varies with temperature changes is applied to the gain current trim and mismatch current trim in a DAC of a quantizing stage of a sub-ranging ADC.

Claims20

Dependent claims

An analog to digital converter (ADC) for providing a temperature compensated reference current to an output resistor ladder comprising:

an operational amplifier (opamp) having a first voltage input and a second voltage input, said opamp configured to output a modulated output signal based on a differential voltage between said first and second voltage inputs;
a first current source coupled to a replica resistor ladder, said replica resistor ladder being a replica of said output resistor ladder, said first current source configured to receive said modulated output signal and to output an adjusted reference current responsive to said modulated output signal;
a second current source configured to mirror said adjusted reference current;
a trim digital to analog converter (DAC) coupled to said second current source, said trim DAC configured to receive the mirrored adjusted reference current and to output a trim current that represents a percentage of said mirrored adjusted reference current, wherein said trim current is combined with said adjusted reference current across said replica resistor ladder at a feedback node between said first current source and said replica resistor ladder to produce a voltage level at said feedback node, said voltage level being fed back to one of said first and second inputs of said operational amplifier;
and
a temperature independent reference voltage source that is provided to the other of said first and second input of said operational amplifier that does not receive said feedback node voltage level.

3 more elements

A temperature compensated digital to analog converter (DAC) comprising:

an input for receiving a digital input signal;
an output for outputting a voltage representative of said digital input signal;
an output resistor connected between said input and said output;
an array of unit cells configured to create a current through said output resistor representative of said digital input signal;
a current gain control circuit comprising:
at least one replica unit cell configured to draw a temperature compensated reference current across at least one replica resistor, the at least one replica resistor configured to replicate said output resistor of the temperature compensated DAC, wherein said at least one replica unit cell is connected to a plurality of output unit cells for producing an output voltage level across said output resistor;
a trim DAC connected to the at least one replica cell, the trim DAC configured to receive the temperature compensated reference current and output a fractional portion of said temperature compensated reference current to produce a temperature compensated trim current, the temperature compensated trim current fed back to said temperature compensated reference current to produce an adjusted reference current;
and
an operational amplifier for amplifying an input reference voltage based on the trimmed adjusted reference current and the at least one replica resistor.

6 more elements

Dependencies are inferred from the claim text.