Circuit calibrating output driving strength of DRAM and method thereof
AssigneeVIA Technologies, Inc.
InventorChi Chang
Life of this patent
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Abstract
A circuit for calibrating the output driving strength of a DRAM and method thereof is provided. A driving strength auto-compensation circuit is used to adjust the resistance value of an output generator inside a memory control chip and match with the target output driving strength of the DRAM. Hence, the input comparator of the memory control chip can be directly used to read from the DRAM and generate an output value so that extra high gain comparators are not required for accurately calibrating the output driving strength of the DRAM. Furthermore, the circuit is easy to implement and the calibrating process can be easily performed.
Claims11
A circuit, for calibrating the output driving strength of a dynamic random access memory (DRAM), comprising:
- a driving strength auto-compensation circuit, outputting at least one auto-compensation control signal according to a reference resistor;
- an output adjustment logic circuit, for selectively receiving a data output or the auto-compensation control signal and then outputting the data output or the auto-compensation signal accordingly;
- an output generator, for generating a corresponding calibration resistance value when the auto-compensation control signal is received;
- and
- an input comparator, having an input terminal for receiving a reference voltage and another input terminal connected to the output terminal of the output generator and the DRAM, wherein the input comparator generates a compare output value for calibrating the output driving strength of the DRAM.
A method of calibrating the output driving strength of a dynamic random access memory (DRAM) through an output generator with a calibration resistance value and an input comparator, wherein one input terminal of the input comparator is connected to a reference voltage while another input terminal of the input comparator is connected to the DRAM and the output generator, the method comprising the steps of:
- turning off the output generator;
- generating a first output value according to the read-out obtained from the DRAM by the input comparator;
- calibrating the output driving strength of a pull-down driving output inside the DRAM when the first output value is a first fixed value;
- and
- calibrating the output driving strength of a pull-up driving output inside the DRAM when the first output value is a second fixed value.
Dependencies are inferred from the claim text.