Multi-stage string DAC
First Claim
1. A string digital-to-analog converter (DAC), comprising:
- a first impedance string including a plurality of N impedance elements forming N+1 nodes;
a switch network coupled to the first impedance string including N+1 switches where each switch selectively connects a unique node of the first impedance string to an input of a second impedance string with each switch having a single input, a single output, and having more than two states including an off state and multiple on states with different switch impedances.
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Abstract
Embodiments of the present invention may provide string DAC architecture with multiple stages for efficient resolution extension. A first stage may include an impedance string (e.g., resistor string). A second stage may include a switch network with each switch having more than two states (impedance values). A third stage may include a string DAC with an impedance string with a set of corresponding switches. In multi-channel embodiments, multiple second and third stages may be provided for each channel while sharing the same first stage (i.e., impedance string). Each second stage switch networks may be controlled based on the relationship between the different channels such as MSB values. Thus, the second stage switch networks may provide different impedance values to compensate for loading effects in multi-channel, multi-stage string DAC designs.
73 Citations
28 Claims
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1. A string digital-to-analog converter (DAC), comprising:
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a first impedance string including a plurality of N impedance elements forming N+1 nodes; a switch network coupled to the first impedance string including N+1 switches where each switch selectively connects a unique node of the first impedance string to an input of a second impedance string with each switch having a single input, a single output, and having more than two states including an off state and multiple on states with different switch impedances. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A multi-channel string DAC, comprising:
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a first string corresponding to respective first portions of a plurality of digital words; a plurality of switch networks, each switch network associated with a respective channel and coupled to the first string, wherein at least one switch in each switch network has more than two states; and a plurality of channel strings, each channel string is coupled to a respective switch network and including an output terminal to output a converted analog signal for the respective channel, wherein the first string is shared by the plurality of channel strings to output the converted analog signal for each channel, wherein each channel corresponds to a separate digital word of the plurality of digital words. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. A method of converting multiple digital words into respective analog voltages in separate channels, comprising:
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receiving the multiple digital words; applying a reference voltage to a shared string; coupling multiple sets of switches to different nodes in the shared string based on first portions of the multiple digital words; configuring impedance values of the coupled switches based on a relationship between the first portions of the multiple digital words; coupling outputs of the multiple sets of switches to channel strings; and outputting the respective analog voltages for each channel, wherein the shared string is shared by the channel strings to output the analog voltages for each channel, and wherein each channel corresponds to a separate digital word of the multiple digital words. - View Dependent Claims (21, 22, 23, 24)
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25. A multi-channel digital to analog converter (DAC), comprising:
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a first stage resistor string; a plurality of second stage resistor strings, each associated with a respective channel; and a plurality of switch networks, each having switches to connect intermediate nodes of the first stage resistor string to end points of a respective second stage resistor string, wherein switches of the switch networks have multiple conductive states, wherein the first stage resistor string is shared by the plurality of second stage resistor strings to output converted analog signals for each channel, and wherein each channel corresponds to a separate digital word. - View Dependent Claims (26, 27, 28)
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Specification