Sampling
There is disclosed current-mode time-interleaved sampling circuitry configured to be driven by substantially sinusoidal clock signals. Such circuitry may be incorporated in ADC circuitry, for example as integrated circuitry on an IC chip. The disclosed circuitry is capable of calibrating itself without being taken off-line.
1. Current-mode circuitry for sampling a current signal, the circuitry comprising:
a root node configured to receive the current signal;
a plurality of first-tier nodes, each of the plurality of first-tier nodes being conductively connectable directly to the root node;
a plurality of subsequent-tier nodes that are provided for each of the first-tier nodes, each of the plurality of subsequent-tier nodes being conductively connectable indirectly to the root node along a respective path via the corresponding first-tier node; and
a steering circuit configured to control connections between the root node and the subsequent-tier nodes so that different packets of charge making up the current signal are steered along different ones of the paths over time;
wherein the steering circuit is configured to employ sinusoidal control signals to control the connections between the root node and the first-tier nodes.
2. The current-mode circuitry of claim 1 , wherein: the steering circuit is configured to employ switched-logic control signals to control connections between the first-tier nodes and the subsequent-tier nodes.
3. The current-mode circuitry of claim 2 , wherein the control signals for controlling the connections between the first-tier nodes and the subsequent-tier nodes have larger peak-to-peak voltages than the peak-to-peak voltages of the control signals for controlling connections between the root node and the first-tier nodes, or longer on-times than the on-times of the control signals for controlling the connections between the root node and the first-tier nodes.
4. The current-mode circuitry of claim 1 , comprising:
a generating circuit configured to generate a sample value for, and on the basis of a characteristic of, each of the packets of charge passing through the subsequent-tier nodes, each sample value being indicative of a value of the current signal corresponding to its packet of charge.
5. Analogue-to-digital conversion circuitry, comprising the current-mode circuitry according to claim 1 .
6. Integrated circuitry, comprising the current-mode circuitry according to claim 1 .
7. An IC chip, comprising the current-mode circuitry according to claim 1 .
8. A method of sampling a current signal in current-mode circuitry, the circuitry having a root node configured to receive the current signal, a plurality of first-tier nodes conductively connectable directly to the root node, and a plurality of subsequent-tier nodes for each of the first-tier nodes, each of the plurality of subsequent-tier nodes being conductively connectable indirectly to the root node along a respective path via the corresponding first-tier node, the method comprising:
controlling connections between the root node and the subsequent-tier nodes so that different packets of charge making up the current signal are steered along different ones of the paths over time; and
employing sinusoidal control signals to control the connections between the root node and the first-tier nodes.
9. The current-mode circuitry of claim 1 , further comprising a reset circuit coupled to one of the first-tier or subsequent-tier nodes, and configured, during a period between successive packets or charge for the one of the first-tier or subsequent-tier nodes, to bring a voltage potential of the one of the first-tier or subsequent-tier nodes to a particular value.