Hybrid digital-to-analog conversion system

摘要

A digital-to-analog conversion (DAC) circuit has a resistor ladder circuit controlled by high order bits and a resistor string circuit controlled by low order bits. The resistor ladder circuit includes a stem resistor and a branch resistor. The stem resistor has a stem resistance, and the branch resistor has a branch resistance that is substantially equal to two times of the stem resistance. The resistor string circuit includes a string current source, a string resistor, and a bridge resistor. The string current source is configured to generate a string current that is based on a ratio of a reference voltage divided by a predetermined resistance. The string resistor has a string resistance that corresponds to the predetermined resistance, and it is configured to selectively receive the string current based on a selection signal decoded from the low order bits.

主权项

1. A digital-to-analog conversion (DAC) circuit comprising:
a string current source configured to generate a string current based on a ratio of a reference voltage divided by a predetermined resistance, the string current source having a string current output lead to deliver the string current; a resistor string having a string resistor coupled across a high string node and a low string node, the string resistor having a string resistance based on the predetermined resistance; a string switch circuit coupled to the string current output lead, the string switch circuit configured to selectively deliver the string current to the string resistor based on a digital input signal; and a bridge resistor coupled between the high string node of the resistor string and a string output node outside of the resistor string, the bridge resistor having a bridge resistance based on the string resistance.