TRANSFORMER COUPLED CLOCK INTERFACE CIRCUIT FOR MEMORY MODULES
The invention is a clock interface circuit for high-speed computer memory modules. It provides improved timing margin due to improved rise and fall times than achieved with present JEDEC specified clock distribution and timing networks. The invention also provides for improved clock and inverse clock symmetry around VREF.
1 . A circuit comprising:
first and second clock inputs;
a transformer coupled to said first and second clock inputs;
the transformer having first and second outputs for coupling to an integrated circuit.
2 . The circuit of claim 1 further including a first DC filter disposed between the clock inputs and the transformer.
3 . The circuit of claim 2 further including a second DC filter disposed between the outputs of the transformer and the integrated circuit.
4 . The circuit of claim 3 further including a divider circuit disposed between the second DC filter and the integrated circuit.
5 . The circuit of claim 4 wherein the first and second clock inputs are differential.
6 . The circuit of claim 5 wherein the integrated circuit is a memory module.
7 . The circuit of claim 6 wherein the transformer is such that lower characteristic impedance transmission lines may be used in the circuit.
8 . The circuit of claim 7 wherein the circuit has improved margins for rise and fall time of the clock inputs.