Programmable high-speed cable with boost device
An HDMI cable carries high speed encoded data which are transmitted differentially over data channels, along with a clock. High-frequency loss and differential skew within a differential signal may be compensated by analog circuits embedded in the cable. These embedded circuits are tuned at production for best performance by observing the quality of the recovered analog signal. The embedded circuits are powered by a combination of power sources, both carried within the cable, and harvested from the high-speed signals themselves.
1. A cable for connecting a transmitting data source device to a receiving data sink device carrying differential signals including:
a boost device for boosting at least one of the differential signals, the boost device comprising:
an input circuit for receiving a raw differential signal from the data source device and outputting a recovered signal;
a deskew circuit with first adjustable parameters for processing the recovered signal into a deskewed signal;
an equalizer circuit with second adjustable parameters for processing the deskewed signal into an equalized signal; and
an output circuit for amplifying the equalized signal into a boosted signal and sending the boosted signal to the data sink device.
2. The cable as described in claim 1 , the boost device further including a parameter memory for retaining the first and second adjustable parameters.
3. The cable as described in claim 2 , wherein the cable further includes a control bus, and wherein the parameter memory is accessible from said control bus.
4. The cable as described in claim 1 , wherein the deskew circuit is an analog differential deskew circuit for adjusting an existing time skew of two polarities of the differential signal by changing the first adjustable parameters.
5. The cable as described in claim 4 , wherein the equalizer circuit comprises a circuit for adjusting a frequency response of the deskewed signal by changing the second adjustable parameters to produce the equalized signal.
6. The cable as described in claim 5 , wherein the equalizer circuit has at least two settings of the second adjustable parameters for adjusting the frequency response.
7. The cable as described in claim 4 , wherein the analog differential deskew circuit comprises:
a number of delay units arranged sequentially;
an analog selector, selecting a composite delay resulting from the delay units that are selected by the analog selector; and
analog switches inserting the composite delay into the polarities of the differential signal.
8. The cable as described in claim 7 , wherein the analog switches are inserting the composite delay into one or the other polarity of the differential signal.
9. The cable as described in claim 8 , wherein each of the analog delay units has a gain which is substantially equal to 1.0.
10. The cable as described in claim 8 , wherein each of the analog delay units comprises one or more amplifiers.
11. The cable as described in claim 10 , wherein each analog delay unit comprises:
first and second amplifiers having a common input, which is the input of the analog delay unit, and their outputs being summed to generate, the output of the analog delay unit;
the first amplifier having a gain of (1.0−Δ), and a delay equal to a predetermined delay value; and
the second amplifier having a gain of Δ and substantially the same delay as the first amplifier.
12. The cable as described in claim 11 , wherein the first amplifier is a follower stage, and the second amplifier has a shunt capacitor for setting the gain of Δ.
13. A boost device for connecting a transmitting data source device to a receiving data sink device, the transmitting data source device sending differential data signals into the boost device, the boost device boosting at least one of the differential data signals, the boost device comprising:
an input circuit for receiving a raw differential signal from the data source device and outputting a recovered signal;
a deskew circuit with first adjustable parameters for processing the recovered signal into a deskewed signal;
an equalizer circuit with second adjustable parameters for processing the deskewed signal into an equalized signal;
an output circuit for amplifying the equalized signal into a boosted signal and sending the boosted signal to the data sink device; and
a parameter memory for retaining the first and second adjustable parameter, and a control input for accessing the parameter memory.
14. A method for a sending differential signals from a transmitting data source device to a receiving data sink device through a cable that includes a boost device for boosting at least one of the differential signals, comprising the steps of:
receiving a raw differential signal from the data source device in an input circuit of the boost device and outputting a recovered signal;
processing the recovered signal in a deskew circuit with first adjustable parameters into a deskewed signal;
processing the deskewed signal in an equalizer circuit with second adjustable parameters into an equalized signal;
amplifying the equalized signal in an output circuit into a boosted signal; and
sending the boosted signal to the data sink device.
15. The method as described in claim 14 , further including the steps of:
adjusting the first and second adjustable parameters; and
storing the first and second adjustable parameters in parameter memory.
16. The method as described in claim 15 , further including a step of accessing the parameter memory from a control input.
17. The method as described in claim 14 , wherein the step of processing the recovered signal includes the step of adjusting an existing time skew of two polarities of the differential signal by changing the first adjustable parameters.
18. The method as described in claim 17 , wherein the step of processing the deskewed signal includes the step of adjusting a frequency response of the deskewed signal by changing the second adjustable parameters.
19. The method as described in claim 17 , wherein the step of changing the first adjustable parameters comprises the steps of:
arranging a number of delay units sequentially;
selecting a composite delay resulting from number of delay units; and
inserting the composite delay into the polarities of the differential signal.
20. The method as described in claim 19 , wherein the step of inserting the composite delay includes inserting the composite delay into one or the other polarity of the differential signal.