Code-controlled voltage divider
First Claim
1. A code-controlled voltage divider circuit, comprising:
- an upper resistor;
a dummy switching transistor, having a conduction path connected in series with the upper resistor between a first reference voltage and an output node, and having a control terminal biased to an on state;
a plurality of lower resistive legs, each comprising;
a lower resistor; and
a switching transistor, having a conduction path connected in series with its associated lower resistor between the output node and a second reference voltage, and having a control terminal connected to a control line, for receiving a bit of a control word.
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Accused Products
Abstract
A code-controlled voltage divider (20) is disclosed. The voltage divider (20) includes an upper portion with a resistor (22) and a dummy switching transistors (23), which is biased to be in an on-state. A lower portion of the voltage divider (20) includes multiple parallel legs, each including a resistor (24) and a corresponding switching transistor (26) that has its gate receiving one bit of a digital control word. A decoder (30) may be provided within the voltage divider (20) to generate the digital control word from an incoming code word, for example from a central processing unit (10). The lower portion resistors (24) of the voltage divider (20) are binary-weighted, and the sizes of the corresponding switching transistors (26) are binary-weighted so that the portion of the series resistance of each parallel leg that is due to the on-resistance of the switching transistor (26) is substantially constant over all of the parallel legs. The upper resistor (22) has a resistance that is related to one of the resistors (24) in the lower portion, and the size of the dummy switching transistor (23) is similarly related to the switching transistor (26) to that resistor'"'"'s switching resistor (24).
23 Citations
25 Claims
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1. A code-controlled voltage divider circuit, comprising:
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an upper resistor; a dummy switching transistor, having a conduction path connected in series with the upper resistor between a first reference voltage and an output node, and having a control terminal biased to an on state; a plurality of lower resistive legs, each comprising; a lower resistor; and a switching transistor, having a conduction path connected in series with its associated lower resistor between the output node and a second reference voltage, and having a control terminal connected to a control line, for receiving a bit of a control word. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A digital system, comprising:
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a central processing unit, for executing operations in response to program instructions, the central processing unit having an output presenting a digital code corresponding to a desired power supply voltage to be applied to at least a portion of the central processing unit; a power supply voltage controller, for generating a power supply voltage for application to the central processing unit responsive to a voltage level received at an input; and a code-controlled voltage divider, having an input receiving the digital code from the central processing unit, and having an output for presenting the voltage level to the power supply voltage controller, comprising; an upper resistor; a dummy switching transistor, having a conduction path connected in series with the upper resistor between a first reference voltage and an output node, and having a control terminal biased to an on state; a plurality of lower resistive legs, each comprising; a lower resistor; and a switching transistor, having a conduction path connected in series with its associated lower resistor between the output node and a second reference voltage, and having a control terminal connected to a control line, for receiving a bit of a control word corresponding to the digital code. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification