DESIGN STRUCTURE FOR RADIATION HARDENED PROGRAMMABLE PHASE FREQUENCY DIVIDER CIRCUIT
A design structure embodied in a machine readable medium includes information for designing, manufacturing and/or testing a programmable phase frequency divider circuit implemented in CMOS technology for space applications. The programmable phase frequency divider consists of three radiation hardened D-type flip flops and combinational logic circuits to provide the feedback controls that allow programmable frequency division ratios from 1 to 8. The radiation hardened D-type flip flop circuits are designed to keep on running properly at GHz frequencies even after a single event upset (SEU) hit. The novel D-type flip flop circuits each have two pairs of complementary inputs and outputs to mitigate SEU'S. The combinational logic circuits are designed to utilize the complementary outputs in such a way that only one of the four dual complementary inputs to any D-type flip flop gets flipped at most after an SEU hit.
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This application is a continuation-in-part of pending U.S. patent application Ser. No. 11/419,008, filed May 18, 2006 and claims the benefit thereof.
BACKGROUND OF THE INVENTION1. Field of the Invention
The invention relates to a radiation hardened programmable phase frequency divider for implementation in deep submicron CMOS technology, and particularly to a design structure embodied in a machine readable medium for designing, manufacturing and/or testing the radiation hardened programmable phase frequency divider circuit.
2. Background Information
CMOS circuits used in space applications are subject to single event upsets (SEU's) as a result of exposure to radiation consisting of alpha particles or neutrons. The charge induced by a single SEU hit can be as high as 1 picoCoulomb (pC), and can have a 2 miliAmpere (1 nA) amplitude with a 1 nanosecond (ns) period. When a programmable phase frequency divider (PPFD) used in such a space application is running at a frequency lower than 200 Megahertz (MHz), an SEU hit with 1 pC charge may not always cause a soft error if the timing of the SEU does not fall within the window for the set and hold times of any of the flip flops in the PPFD. In such case, a dual interlocked cell (DICE) type flip flop design, such as the one described in Weizhong Wang and Haiyan Gong,” Sense Amplifier Based RADHARD Flip Flop Design,” IEEE Transactions on Nuclear Science, Vol. 51, No. 6 (December 2004), may be used. However, a PPFD fabricated in deep micron technology can run at frequencies in the Gigahertz (GHZ) range. In this case, the vulnerable timing window for set and hold of the PPFD's D-type flip flops (DFF's) will always be covered by the typical 1 ns period of an SEU hit. Under these circumstances, what is required is an innovative radiation hardening technique to ensure that the PPFD continues to function properly in a radiation environment.
SUMMARY OF THE INVENTIONIt is, therefore, a principle object of this invention to provide a radiation hardened programmable phase frequency divider designed for deep submicron CMOS technology.
It is another object of the invention to provide a radiation hardened programmable phase frequency divider that solves the above mentioned problems.
It is a further object of the invention to provide a design structure embodied in a machine readable medium in which information relating to the design, manufacture and/or testing of the radiation hardened programmable phase frequency divider resides.
These and other objects of the present invention are accomplished by the radiation hardened programmable phase frequency divider for deep submicron CMOS technology that is disclosed herein.
In a first aspect of the invention, a radiation hardened master latch includes: a first master latch half circuit having a clock input, first and second complementary data inputs, complementary feedback inputs and complementary data outputs; and a second master latch half circuit identical to the first master latch half circuit and having a clock input, first and second complementary data inputs, complementary feedback inputs and complementary data outputs. In the master latch, the respective clock inputs of the first and second master latch half circuits are connected together in parallel; the respective first and second complementary data inputs of the first and second master latch half circuits are connected together in parallel; the complementary data outputs of the first master latch half circuit are cross connected to the complementary feedback inputs of the second master latch half circuit; and the complementary data outputs of the second master latch half circuit are cross connected to the complementary feedback inputs of the first master latch half circuit. In the absence of SEU's, the first and second complementary data inputs to the master latch have nominally the same input voltage levels. Operation of the master latch is immune to a single event upset affecting at most one of the four complementary data inputs to the master latch. The master latch half circuits are preferably implemented in CMOS technology capable of operating at GHz frequencies.
In another aspect of the invention, a radiation hardened slave latch includes: a first slave latch half circuit having first and second complementary data inputs, complementary feedback inputs and complementary data outputs; and a second slave latch half circuit identical to the first slave latch half circuit and having first and second complementary data inputs, complementary feedback inputs and complementary data outputs. In the slave latch, the first complementary data inputs of the first slave latch half circuit and the second complementary data inputs of the second slave latch half circuit are connected together in parallel; the second complementary data inputs of the first slave latch half circuit and the first complementary data inputs of the second slave latch half circuit are connected together in parallel; the complementary data outputs of the first slave latch half circuit are cross connected to the complementary feedback inputs of the second master latch half circuit; and the complementary data outputs of the second master latch half circuit are cross connected to the complementary feedback inputs of the first master latch half circuit. In the absence of SEU's, the first and second complementary data inputs to the slave latch have nominally the same input voltage levels. Operation of the slave latch is immune to a single event upset affecting at most one of the four complementary data inputs to the slave latch. The slave latch half circuits are preferably implemented in CMOS technology capable of operating at GHz frequencies.
In yet another aspect of the invention, a radiation hardened D-type flip flop includes: a master latch, as described above, having a clock input, first and second complementary data inputs, and first and second complementary data outputs; and a slave latch, as described above, having first and second complementary data inputs, and first and second complementary data outputs. In the D-type flip flop, the first complementary data outputs of the master latch are connected to the first complementary data inputs of the slave latch, and the first complementary data outputs of the master latch are connected to the first complementary data inputs of the slave latch. In the absence of SEU's, the first and second complementary data inputs to the D-type flip flop have nominally the same input voltage levels. Operation of the D-type flip flop is immune to a single event upset affecting at most one of the four complementary data inputs to the slave latch. The master latch and slave latch circuits are preferably implemented in CMOS technology capable of operating at GHz frequencies.
In a further aspect of the invention, a radiation hardened programmable phase frequency divider is comprised of: a plurality of D-type flip flops, as described above, each having a clock input, first and second complementary data inputs, and first and second complementary data outputs; a first combinational logic block connected to the first complementary data inputs and the first complementary data outputs of the plurality of D-type flip flops; and a second combinational logic block identical to the first combinational logic block, and connected to the second complementary data inputs and the second complementary data outputs of the plurality of D-type flip flops. The clock inputs of the plurality of D-type flip flops are connected to a common clock source. The first and second combinational logic blocks are adapted to provide for frequency division of the clock source in accordance with a division number inputted to the combinational logic blocks. The inventive programmable phase frequency divider also preferably includes a third combinational logic block connected to the first combinational logic block for outputting a pulse train representing the clock source frequency divided in accordance with the division number. The plurality of D-type flip flops and the combinational logic blocks are preferably implemented in CMOS technology capable of operating at GHz frequencies.
In yet a further aspect of the invention, the radiation hardened programmable phase frequency divider resides in a design structure embodied in a machine readable medium storing information for designing, manufacturing and/or testing the programmable phase frequency divider circuit. The design structure may comprise a netlist which describes the programmable phase frequency divider circuit. The design structure may also reside on the machine readable medium as a data format used for the exchange of layout data for integrated circuits. Further, the design structure may include test data files, characterization data, verification data and/or design specifications.
The invention will now be described in more detail by way of example with reference to the embodiments shown in the accompanying figures. It should be kept in mind that the following described embodiments are only presented by way of example and should not be construed as limiting the inventive concept to any particular physical configuration.
Further, if used and unless otherwise stated, the terms “upper,” “lower,” “front,” “back,” “over,” “under,” and similar such terms are not to be construed as limiting the invention to a particular orientation. Instead, these terms are used only on a relative basis.
The present invention is directed to a radiation hardened (RADHARD) programmable phase frequency divider designed to be implemented in deep submicron CMOS technology.
In a preferred embodiment, a PPFD consists of 3 RADHARD D-type flip flops (DFF's) and combinational logic circuits to provide the feedback controls that allow programmable frequency division ratios from 1 to 8. The RADHARD DFF circuits are designed to keep on running properly at GHz frequencies even after a SEU hit. The novel DFF circuits each have two pairs of complementary inputs and outputs to mitigate single event upsets. The combinational logics are designed to utilize the complementary outputs in such a way that only one of two pairs of complementary inputs to any DFF gets flipped at most after an SEU hit. Therefore, a RADHARD PPFD that is immune to SEU's is achieved. A detailed description of the preferred embodiment follows.
RADHARD Flip Flop Design
Transistors T9 and T11 each have one drain-source region coupled to the high voltage source VDD and the other source-drain region coupled to output Q. Similarly, transistor T8 and T10 each have one drain-source region coupled to the high voltage source VDD and the other source-drain region coupled to complementary output QB. An equalization transistor T12 has one drain-source region coupled to output Q and its second drain source region to complementary output QB. The gates of transistors T10, T11 and T12 are coupled to the clock input CLK through an inverter 12.
Transistors T4, T5, T6 and T7 form half of the master latch's interconnected flip flop circuits. Transistors T6 and T7 each have one drain-source region coupled to output Q and the other source-drain region coupled to a data node DATA. Transistors T4 and T5 each have one drain-source region coupled to complementary output QB and the other source-drain region coupled to a complementary data node DATAB. The gates of T5 and T6 are cross coupled to the outputs Q and QB, respectively. The feedback input Q_DUAL from the other half of the master latch is coupled the gates of both T4 and T8. In similar fashion, the complementary feedback input QB_DUAL from the other half of the master latch is coupled the gates of both T7 and T9.
The data input portion of the master latch half circuit includes transistors T0, T1, T2, T3, T13, T14 and T15. The clock input is coupled to the gates of both T13 and T14 through an inverter 14. One drain-source region of each of T13 and T14 is coupled to a low voltage, which is at ground potential GND in the preferred embodiment. The second drain source region of T13 is connected to node N1 and the second drain-source region of T14 is connected to node N2. One drain-source region of each of T3 and T0 is coupled to node N1, and the second drain source regions of T3 and T0 are connected to data nodes DATA and DATAB, respectively. Similarly one drain-source region of each of T2 and T1 is coupled to node N2, and the second drain source regions of T2 and T1 are connected to data nodes DATA and DATAB, respectively. An equalization transistor T15 has one drain-source region coupled to data node DATA and its second drain source region to complementary data node DATAB. The gate of T15 is coupled to the high potential VDD. To complete the circuit, complementary data inputs DIN_0 and DINB_0 are coupled to the gates of transistors T0 and T3, respectively, while dual complementary data inputs DIN_1 and DINB_1 are coupled to the gates of T1 and T2, respectively.
In normal operation, the inputs DIN_0, DIN_1 have the same voltage level, while DINB_0, DINB_1 have the same voltage level that is complementary to DIN_0, DIN_1. When CLK is high, Q, QB are precharged to high through T10, T11 with T12 for equalization. Q_DUAL, QB_DUAL are similar to Q, QB (see
In this innovative scheme of dual complementary inputs, T0, T1, T13 and T2, T3 T14 (see the dashed line box 16 in
As shown in
The slave latch half circuit 30 shown in
With regard to the transistor string in parallel with T6, transistor T2 has one drain-source region coupled to output Q and the other drain-source region coupled to one drain-source region of transistor T1. The other drain-source region of T1 is in turn coupled to one drain-source region of transistor T0, while the other drain-source region of T0 is coupled to the low potential GND. Similarly, with regard to the transistor string in parallel with T7, transistor T5 has one drain-source region coupled to output QB and the other drain-source region coupled to one drain-source region of transistor T4. The other drain-source region of T4 is in turn coupled to one drain-source region of transistor T3, while the other drain-source region of T3 is coupled to the low potential GND.
The gate connections for the main output transistors and the parallel transistor strings are as follows: input DIN is coupled to the gates of transistors T15 and T5; input DINB is coupled to the gates of transistors T14 and T2; data line DD, at the output of NOR gate 31, is coupled to the gates of transistors T11 and T7; data line DDB, at the output of NOR gate 32, is coupled to the gates of transistors T8 and T6; output Q is coupled to the gates of transistors T12 and T3; output QB is coupled to the gates of transistors T9 and T0; feedback input Q_DUAL, from the other half of the slave latch, is coupled to the gates of transistors T13 and T4; and complementary feedback input QB_DUAL is coupled to the gates of transistors T10 and T1.
In the normal operation of the RADHARD slave latch half circuit 30, when the clock CLK is high, all four inputs, DIN_DUAL, DINB_DUAL, DIN, DINB, are pre-charged to high; all four output transistors, T6, T7, T14, T15 are turned off and all of transistors T5, T8 and T2, T11 are turned on to hold the states of outputs Q and QB. When the clock CLK transitions from high to low, T6, T15, T2, T11 will be turned on and T7, T14, T5, T8 turned off dependent on whether DINB, DINB_DUAL go to high and DIN, DIN_DUAL go to low, or vice versa. The two 2-input NOR gates 31, 32 are implemented to avoid the effect of two node flips with one sensitive node hit, as discussed in the paper by Wang and Gong, cited above.
The innovative scheme implemented in the RADHARD slave latch half circuit 30 shown in
RADHARD Programmable Frequency Divider Design
DIN=Function (Un, Un−1, . . . , U0); and
DINB=Function (Vn, Vn−1, . . . , V0),
where Ui and Vi are the complementary outputs of ith DFF.
Hence, if there is an SEU hit to a node in the combinational logic blocks, there will not be a case of two nodes flipped with one hit such that both DIN and DINB get flipped. Therefore, there will always be none or at most one of the 4 inputs getting flipped for each hit. The RADHARD DFF 50 is able to work properly even if there is one of the 4 inputs getting flipped. Consequently, the PPFD 60 employing the above described novel circuit schemes is RADHARD for SEU effects.
As shown in
Simulation results using PowerSpice™ under conditions representing all combinations of power, voltage and temperature extremes have confirmed that the above-described designs are solid and robust.
Design Structure
Design process 710 may include using a variety of inputs; for example, inputs from library elements 730 which may house a set of commonly used elements, circuits, and devices, including models, layouts, and symbolic representations, for a given manufacturing technology (e.g., different technology nodes, 32 nm, 45 nm, 90 nm, etc.), design specifications 740, characterization data 750, verification data 760, design rules 770, and test data files 785 (which may include test patterns and other testing information). Design process 710 may further include, for example, standard circuit design processes such as timing analysis, verification, design rule checking, place and route operations, etc. One of ordinary skill in the art of integrated circuit design can appreciate the extent of possible electronic design automation tools and applications used in design process 710 without deviating from the scope and spirit of the invention. The design structure of the invention is not limited to any specific design flow.
Design process 710 preferably translates an embodiment of the invention as shown in
The above-described designs provide the essential techniques for radiation hardening of combinational and sequential logic circuits required to operate at GHz frequencies. The obvious drawbacks of these techniques is larger circuit area and higher power consumption.
It should be understood that the invention is not necessarily limited to the specific process, arrangement, materials and components shown and described above, but may be susceptible to numerous variations within the scope of the invention. For example, although the above-described exemplary aspects of the invention are believed to be particularly well suited for programmable phase frequency dividers typically use in phased-locked loops, it is contemplated that the concepts of the presently disclosed sequential and combinational logic circuits can be used in other RADHARD logic systems requiring the mitigation of SEU events. Moreover, the proposed circuit schemes, while presented in the context of existing CMOS technologies; are device independent and equally applicable to other current and future logic technologies.
It will be apparent to one skilled in the art that the manner of making and using the claimed invention has been adequately disclosed in the above-written description of the preferred embodiments taken together with the drawings.
It will be understood that the above description of the preferred embodiments of the present invention are susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.
Claims
1. A design structure embodied in a machine readable medium for designing, manufacturing or testing a radiation hardened programmable phase frequency divider circuit, the programmable phase frequency divider circuit comprising:
- a plurality of radiation hardened D-type flip flops each having a clock input connected to a common clock source, first and second data inputs, first and second complementary data inputs, first and second data outputs, and first and second complementary data outputs;
- a first combinational logic block connected to the first data inputs, first complementary data inputs, first data outputs and first complementary data outputs of the plurality of D-type flip flops;
- a second combinational logic block identical to the first combinational logic block, and connected to the second data inputs, second complementary data inputs, second data outputs and second complementary data outputs of the plurality of D-type flip flops; and;
- a third combinational logic block connected to the first combinational logic block for outputting a pulse train representing the clock source frequency divided in accordance with a division number inputted to the first and second combinational logic blocks,
- wherein operation of each of the D-type flip flop is immune to a single event upset affecting at most one of its four data inputs.
2. The design structure of claim 1, wherein the data inputs, DIN, and the complementary inputs, DINB, generated by the first and second combinational logic blocks are related to the data outputs and the complementary data outputs from the D-type flip flops by the equations:
- DIN=Function (Un, Un−1,..., U0); and
- DINB=Function (Vn, Vn−1,..., VO),
- where Ui and Vi are respectively the data output and the complementary data output of the ith D-type flip flop.
3. The design structure of claim 1, wherein each of the radiation hardened D-type flip flops is comprised of:
- a master latch having a clock input, first and second data inputs, first and second complementary data inputs, first and second data outputs, and first and second complementary data outputs; and
- a slave latch having first and second data inputs, first and second complementary data inputs, first and second data outputs, and first and second complementary data outputs,
- wherein
- the clock input, first and second data inputs, and first and second complementary data inputs of the master latch serve respectively as the clock input, first and second data inputs, and first and second complementary data inputs of the D-type flip-flop,
- the first data output and the first complementary data output of the master latch are connected respectively to the first data input and the first complementary data input of the slave latch,
- the second data output and the second complementary data output of the master latch are connected respectively to the second data input and the second complementary data input of the slave latch, and
- the first and second data outputs, and first and second complementary data outputs of the slave latch serve respectively as the first and second data outputs, and first and second complementary data outputs of the D-type flip-flop.
4. The design structure of claim 3, wherein each radiation hardened master latch is comprised of:
- a first master latch half circuit having a clock input, first and second data inputs, first and second complementary data inputs, a feedback input, a complementary feedback input, a data output, and a complementary data output; and
- a second master latch half circuit identical to the first master latch half circuit and having a clock input, first and second data inputs, first and second complementary data inputs, a feedback input, a complementary feedback input, a data output, and a complementary data output,
- wherein
- the respective clock inputs of the first and second master latch half circuits are connected together in parallel, and serve as the clock input to the master latch,
- the respective first and second data inputs and first and second complementary data inputs of the first and second master latch half circuits are connected together in parallel, and serve respectively as the first and second data inputs and first and second complementary data inputs of the master latch,
- the data output and the complementary data output of the first master latch half circuit are connected respectively to the feedback input and the complementary feedback input of the second master latch half circuit,
- the data output and the complementary data output of the second master latch half circuit are connected respectively to the feedback input and the complementary feedback input of the first master latch half circuit.
- the data output and the complementary data output of the first master latch half circuit serve respectively as the first data output and the first complementary data output of the master latch, and
- the data output and the complementary data output of the second master latch half circuit serve respectively as the second data output and the second complementary data output of the master latch.
5. The design structure of claim 4, wherein each of the master latch half circuits is comprised of:
- first and second pre-charging transistors each having one drain-source region coupled to a high voltage source and the other source-drain region coupled to the data output;
- third and fourth pre-charging transistors each having one drain-source region coupled to the high voltage source and the other source-drain region coupled to the complementary data output;
- a first equalization transistor having one drain-source region coupled to the data output and the other drain source region coupled to the complementary data output, the gates of first equalization transistor and the second and third pre-charging transistors all being coupled to the clock input through a first inverter;
- first and second latch transistors each having one drain-source region coupled to the data output and the other source-drain region coupled to a first data node;
- third and fourth latch transistors each having one drain-source region coupled to the complementary data output and the other source-drain region coupled to a second data node, the gates of the third and second latch transistors being cross coupled to the data output and the complementary data output, respectively, the gates of both the fourth latch transistor and the fourth pre-charging transistor being coupled to the feedback input, and the gates of both the first latch transistor and the first pre-charging transistor being coupled to the complementary feedback input;
- a first clocking transistor having one drain-source region coupled to ground potential, the other drain-source region coupled to a first clocking node and the gate coupled to the clock input through a second inverter;
- a second clocking transistor having one drain-source region coupled to ground potential, the other drain-source region coupled to a second clocking node and the gate coupled to the gate of the first clocking transistor;
- a first data input transistor having one drain-source region coupled to the first data node, the other drain-source region coupled to the first clocking node and the gate coupled to the first complementary data input;
- a second data input transistor having one drain-source region coupled to the first data node, the other drain-source region coupled to the second clocking node and the gate coupled to the second complementary data input;
- a third data input transistor having one drain-source region coupled to the second data node, the other drain-source region coupled to the second clocking node and the gate coupled to the second data input;
- a fourth data input transistor having one drain-source region coupled to the second data node, the other drain-source region coupled to the first clocking node and the gate coupled to the first data input;
- a second equalization transistor having one drain-source region coupled to the first data node, the other drain-source region coupled to the second data node and the gate coupled to the high potential.
6. The design structure of claim 3, wherein each radiation hardened slave latch is comprised of:
- a first slave latch half circuit having first and second data inputs, first and second complementary data inputs, a feedback input, a complementary feedback input, a data output, and a complementary data output; and
- a second slave latch half circuit identical to the first slave latch half circuit and having first and second data inputs, first and second complementary data inputs, a feedback input, a complementary feedback input, a data output, and a complementary data output,
- wherein
- the first data input and the first complementary data input of the first slave latch half circuit are respective connected in parallel with second data input and the second complementary data input of the second slave latch half circuit, and serve respectively as the second data input and second complementary data input of the slave latch,
- the second data input and the second complementary data input of the first slave latch half circuit are respectively connected in parallel with the first data input and the first complementary data input of the second slave latch half circuit, and serve respectively as the first data input and first complementary data input of the slave latch,
- the data output and the complementary data output of the first slave latch half circuit are connected respectively to the feedback input and the complementary feedback input of the second slave latch half circuit,
- the data output and the complementary data output of the second slave latch half circuit are connected respectively to the feedback input and complementary feedback input of the first slave latch half circuit,
- the data output and the complementary data output of the first slave latch half circuit serve respectively as the first data output and the first complementary data output of the slave latch, and
- the data output and the complementary data output of the second slave latch half circuit serve respectively as the second data output and the second complementary data output of the slave latch.
7. The design structure of claim 6, wherein each of the slave latch half circuits is comprised of:
- a first NOR gate having a first input coupled to the first complementary data input and a second input coupled to the second complementary data input;
- a second NOR gate having a first input coupled to the first data input and a second input coupled to the second data input;
- a first output transistor having one drain-source region coupled to a source of high potential and the other drain-source region coupled to the data output;
- a second output transistor having one drain-source region coupled to the data output and the other drain-source region coupled to ground potential;
- a third output transistor having one drain-source region coupled to the source of high potential and the second drain-source region coupled to the complementary data output;
- a fourth output transistor having one drain-source region coupled to the first complementary output and the other drain-source region coupled to ground potential;
- a first series string of three transistors connected in with parallel with the first output transistor, the first string including a first transistor having one drain-source region coupled to the source of high potential, a second transistor having one drain-source region coupled to the other drain-source region of the first transistor, and a third transistor having one drain-source region coupled to the other drain-source region of the second transistor and the other drain-source region coupled to the data output;
- a second series string of three transistors connected in with parallel with the second output transistor, the second string including a first transistor having one drain-source region coupled to the data output, a second transistor having one drain-source region coupled to the other drain-source region of the first transistor, and a third transistor having one drain-source region coupled to the other drain-source region of the second transistor and the other drain-source region coupled to ground potential;
- a third series string of three transistors connected in with parallel with the third output transistor, the third string including a first transistor having one drain-source region coupled to the source of high potential, a second
- transistor having one drain-source region coupled to the other drain-source region of the first transistor, and a third transistor having one drain-source region coupled to the other drain-source region of the second transistor and the other drain-source region coupled to the complementary data output; and
- a fourth series string of three transistors connected in with parallel with the fourth output transistor, the fourth string including a first transistor having one drain-source region coupled to the complementary data output, a second transistor having one drain-source region coupled to the other drain-source region of the first transistor, and a third transistor having one drain-source region coupled to the other drain-source region of the second transistor and the other drain-source region coupled to ground potential,
- wherein
- the first data input is coupled to the gates of third output transistor and the first transistor in the fourth series string,
- the first complementary data input is coupled to the gates of the first output transistor and the first transistor in the second series string,
- output of the first NOR gate is coupled to the gates of the fourth output transistor and the third transistor in the third series string,
- output of the second NOR gate is coupled to the gates of the second output transistor and the third transistor in the second series string,
- the data output is coupled to the gates of the second transistor in the third series string and the third transistor in the fourth series string,
- the complementary output is coupled to the gates of the second transistor in the first series string and the third transistor in the second series string,
- the feedback input is coupled to the gates of the first transistor in the third series string and the second transistor in the fourth series string, and
- the complementary feedback input is coupled to the gates of the first transistor in the first series string and the second transistor in the second series string.
8. The design structure of claim 1, wherein the programmable phase frequency divider circuit is implemented in CMOS technology.
9. The design structure of claim 1, wherein the design structure comprises a netlist which describes the programmable phase frequency divider circuit.
10. The design structure of claim 1, wherein the design structure resides on the machine readable medium as a data format used for the exchange of layout data for integrated circuits.
11. The design structure of claim 1, wherein the design structure includes at least one of test data files, characterization data, verification data and design specifications.
Type: Application
Filed: Jun 4, 2008
Publication Date: Sep 25, 2008
Applicant: International Business Machines Corporation (Armonk, NY)
Inventor: William Yeh-Yung MO (Los Altos, CA)
Application Number: 12/132,863
International Classification: G06F 17/50 (20060101);