Programmable two-way fast DVC control circuit
A linear regulator which has a pass device coupled between an input voltage level and an output node, a voltage divider circuit for generating a feedback voltage that depends on an output voltage at the output node, and an operational amplifier for controlling the pass device, the operational amplifier receiving the feedback voltage and a reference voltage at its inputs is presented. The operational amplifier has: an input stage that receives the feedback voltage and the reference voltage at its inputs, an amplifier stage that receives an output of the input stage at its input, and a current injection circuit for sourcing current into an intermediate node between the input stage and the amplifier stage, or sinking a current from the intermediate node. The disclosure further relates to a corresponding method of operating a linear regulator.
1. A linear regulator, comprising:
a pass device coupled between an input voltage level and an output node;
a voltage divider circuit for generating a feedback voltage that depends on an output voltage at the output node; and
an operational amplifier for controlling the pass device, the operational amplifier receiving the feedback voltage and a reference voltage at its inputs,
wherein the operational amplifier comprises:
an input stage that receives the feedback voltage and the reference voltage at its inputs;
an amplifier stage that receives an output of the input stage at its input;
a current injection circuit for sourcing current into an intermediate node between the input stage and the amplifier stage, or sinking a current from the intermediate node; and
a Miller capacitance that is formed between the intermediate node and the output node,
wherein the current injection circuit is for compensating for current flowing through the Miller capacitance,
wherein the voltage divider circuit comprises a variable resistance element that is arranged such that varying a resistance of the variable resistance element changes a divider ratio of the voltage divider circuit, and
wherein the current injection circuit and the variable resistance element operate under control of the same control signal.
2. The linear regulator according to claim 1 , wherein the current injection circuit comprises a controllable current source for sourcing a current into the intermediate node and/or a controllable current sink for sinking a current from the intermediate node.
3. The linear regulator according to claim 2 , wherein the controllable current source and the controllable current sink are iDACs.
4. The linear regulator according to claim 1 , wherein the voltage divider circuit has a variable divider ratio; and
wherein the current injection circuit is jointly controlled with the voltage divider circuit.
5. The linear regulator according to claim 1 , wherein the current injection circuit and the variable resistance element are jointly controlled such that the current injection circuit sources current to the intermediate node when the divider ratio is increased.
6. The linear regulator according to claim 1 , wherein the current injection circuit and the variable resistance element are jointly controlled such that the current injection circuit sinks current from the intermediate node when the divider ratio is decreased.
7. The linear regulator according to claim 1 , wherein the current injection circuit is controlled in such manner that it sinks current from the intermediate node during ramp-up of the output voltage.
8. The linear regulator according to claim 1 , wherein the current injection circuit is controlled in such manner that it sources current to the intermediate node during ramp-down of the output voltage.
9. A method of operating a linear regulator, wherein the linear regulator comprises:
a pass device coupled between an input voltage level and an output node;
a voltage divider circuit for generating a feedback voltage that depends on an output voltage at the output node; and
an operational amplifier for controlling the pass device, wherein the operational amplifier receives the feedback voltage and a reference voltage at its inputs and comprises: an input stage that receives the feedback voltage and the reference voltage at its inputs, an amplifier stage that receives an output of the input stage at its input, and a Miller capacitance that is formed between an intermediate node between the input stage and the amplifier stage and the output node,
the method comprising:
sourcing a current into the intermediate node, or sinking a current from the intermediate node, for compensating for current flowing through the Miller capacitance,
wherein the voltage divider circuit comprises a variable resistance element that is arranged such that varying a resistance of the variable resistance element changes a divider ratio of the voltage divider circuit, and
the method further comprising:
operating the variable resistance element and a current injection circuit for sourcing or sinking of the current under control of the same control signal.
10. The method according to claim 9 , wherein the current is sourced into the intermediate node by a controllable current source for sourcing the current into the intermediate node and/or the current is sunk from the intermediate node by a controllable current sink for sinking the current from the intermediate node.
11. The method according to claim 10 , wherein the controllable current source and the controllable current sink are iDACs.
12. The method according to claim 9 , wherein the voltage divider circuit has a variable divider ratio; and
the method comprises:
jointly controlling the voltage divider circuit and a current injection circuit for sourcing or sinking of the current.
13. The method according to claim 9 , comprising:
sourcing current to the intermediate node when the divider ratio is increased.
14. The method according to claim 9 , comprising:
sinking current from the intermediate node when the divider ratio is decreased.