Voltage-to-Current Converter with Tuned Resistor Array
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Solution Overview
Problem
Conventional voltage-to-current converters in digital-to-analog converters (DACs) face inaccuracies due to on-resistance variations and leakage currents across process-voltage-temperature (PVT) conditions, leading to unstable output current and voltage references, which limits DAC performance in advanced wireless standards like LTE.
Innovation Solution
A reference-tag-tuning-based voltage-to-current converter architecture is implemented, where an amplifier with input terminals and an array of resistors adjusts gain by selecting resistors to minimize errors caused by switch leakage and on-resistance variations, using short switches to maintain minimal current flow and ensure accurate tuning voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage-to-current converter is used, then the DAC can operate, but the output current and voltage reference show large variations and inaccuracies due to on-resistance variation and leakage current across PVT conditions
Solution Approach 1:
An operational amplifier is introduced as an intermediary component to actively regulate the voltage reference node. The amplifier compensates for variations caused by switch on-resistance and leakage current by dynamically adjusting the voltage at the reference node, thereby maintaining stable and accurate output current across PVT conditions
Solution Approach 2:
The operational amplifier implements a feedback mechanism by continuously monitoring the voltage at the reference node and adjusting its output to maintain the desired voltage level. This feedback loop compensates for disturbances caused by switch parameter variations, ensuring reliable and precise current output
2Adaptability or versatility
If gain setting switches are used to adjust amplifier gain, then the DAC can be tuned, but switch leakage current and on-resistance variation cause tuning inaccuracies
Solution Approach 1:
The operational amplifier acts as a mediator between the gain setting switches and the output current. By buffering the voltage reference node, the amplifier isolates the tuning mechanism from the sensitive current output, preventing switch leakage and on-resistance variations from directly affecting tuning accuracy
Solution Approach 2:
The voltage buffer provided by the operational amplifier cushions the tuning voltage against the harmful effects of switch parameter variations before these variations can propagate to the output current. This protective buffering ensures that tuning inaccuracies are minimized
Data Source
AI summary
A converter including: an amplifier having first and second input terminals and an output terminal, the first input terminal configured to receive a reference voltage; an array of resistors configured to generate a tuning voltage; and a first plurality of switches coupled to the second input terminal of the amplifier and the array of resistors, the first plurality of switches configured to adjust a gain of the amplifier by selecting at least one resistor in the array of resistors to connect to the second input terminal of the amplifier.