Method and system for saving power in a real time hardware processing unit
The present invention provides an analog-digital hybrid architecture, which performs 256 multiplications and additions at a time. The system comprises 256 Processing Elements (PE) ( 108 ), which are arranged in a matrix form (16 rows and 16 columns). The digital inputs ( 110 ) are converted to analog signal ( 114 ) using digital to analog converters (DAC) ( 102 ). One PE ( 108 ) produces one analog output ( 115 ) which is nothing but the multiplication of the analog input ( 114 ) and the digital weight input ( 112 ). The implementation of PE is done by using i) capacitors and switches and ii) resistor and switches. The outputs from multiple PEs ( 108 ) in a column are connected together to produce one analog MAC output ( 116 ). In the similar manner, the system produces 16 MAC outputs ( 118 ) corresponding to 16 columns. Analog to digital converters (ADC) ( 104 ) are used to convert the analog MAC output ( 116 ) to digital form ( 118 ).
1. A system for saving power in a real time hardware processing unit, said system comprising:
a first circuit and a second circuit;
wherein the first circuit is substantially identical to the second circuit;
wherein the first circuit comprising:
a plurality of binary weighted capacitors;
a plurality of switches;
wherein the plurality of switches are adapted to connect the corresponding plurality of binary weighted capacitors;
a two phase non-overlapping clock signal input defined a phase one non-overlapping clock signal input, a phase two non-overlapping clock signal input;
an analog input defined a first analog input (Vinp), a second analog input (Vinn);
a plurality of digital input bits;
wherein each the digital input bit is adapted to connect the corresponding switch such that each the digital input bit is adapted to control the corresponding switch;
wherein a most significant bit of the plurality of digital input bits determines a first analog input (Vinp) if the most significant bit is zero;
wherein the most significant bit of the plurality of digital input bits determines a second analog input (Vinn) if the most significant bit is one;
the plurality of binary weighted capacitors adapted to connect the first analog input during the phase one non-overlapping clock signal input if the most significant bit of the plurality of digital inputs is zero and the plurality of digital inputs of the corresponding plurality of binary weighted capacitors are ones;
the plurality of binary weighted capacitors adapted to reset during the phase one non-overlapping clock signal input if the plurality of digital inputs of the corresponding plurality of binary weighted capacitors are zero;
or the plurality of binary weighted capacitors adapted to connect the second analog input during the phase one non-overlapping clock signal input if the most significant bit of the plurality of digital inputs is one and the plurality of digital inputs of the corresponding plurality of binary weighted capacitors are ones;
and the plurality of binary weighted capacitors adapted to reset during the phase one non-overlapping clock signal input if the plurality of digital inputs of the corresponding plurality of binary weighted capacitors are zeros;
and the plurality of capacitors adapted to connect in parallel during the phase two non-overlapping clock signal input such that the plurality of capacitors generate a first analog output( 206 a );
wherein the second circuit comprising:
a plurality of binary weighted capacitors;
a plurality of switches;
wherein the plurality of switches are adapted to connect the corresponding plurality of binary weighted capacitors;
a two phase non-overlapping clock signal input defined as a phase one non-overlapping clock signal input, a phase two non-overlapping clock signal input;
a differential analog input defined as a first analog input (Vinp), a second analog input (Vinn);
a plurality of digital input bits;
wherein each the digital input bit is adapted to connect the corresponding switch such that each the digital input bit is adapted to control the corresponding switch;
wherein a most significant bit of the plurality of digital input bits determines a second analog input (Vinn) if the most significant bit is zero;
wherein the most significant bit of the plurality of digital input bits determines a first analog input (Vinp) if the most significant bit is one;
the plurality of binary weighted capacitors adapted to connect the first analog input during the phase one non-overlapping clock signal input if the most significant bit of the plurality of digital inputs is one and the plurality of digital inputs of the corresponding plurality of binary weighted capacitors are ones;
and the plurality of binary weighted capacitors adapted to reset during the phase one non-overlapping clock signal input if the plurality of digital inputs of the corresponding plurality of binary weighted capacitors are zero; or
the plurality of binary weighted capacitors adapted to connect the second analog input during the phase one non-overlapping clock signal input if the most significant bit of the plurality of digital inputs is zero and the plurality of digital inputs of the corresponding plurality of binary weighted capacitors are ones;
and the plurality of binary weighted capacitors adapted to reset during the phase one non-overlapping clock signal input if the plurality of digital inputs of the corresponding plurality of binary weighted capacitors are zeros; and
the plurality of capacitors adapted to connect in parallel during the phase two non-overlapping clock signal input such that the plurality of capacitors generate a second analog output.
2. The system of claim 1 , wherein the analog input is a fully differential analog input.
3. The system of claim 1 , wherein the digital input is an eight bit digital input in sign magnitude form.
4. The system of claim 1 further comprising a common mode voltage (VCM), wherein the common mode voltage is adapted to connect one of a terminals of the plurality of capacitors.
5. The system of claim 1 , wherein the most significant bit of the plurality of digital input bits is a sign bit.