Current-Mode MAC Unit for Linear Low-Power Signal Accumulation
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Solution Overview
Problem
Hardware systems performing MAC operations face challenges with non-linear conversions due to voltage mode DACs and voltage-to-current conversions, leading to reduced dynamic range and increased power consumption, along with the need for additional filters and active stages.
Innovation Solution
The implementation of a mixed mode analog-digital architecture using current mode devices as filters, which eliminates the need for active filters and drivers, enhancing linearity and reducing device size and power consumption, while providing a direct interface with non-volatile memory types like MRAM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage mode DACs are used to perform MAC operations, then the system can perform multiplication and addition operations, but non-linear conversions occur leading to reduced dynamic range
Solution Approach 1:
The patent replaces voltage mode DACs with current mode DACs. Current mode operation eliminates the non-linear voltage-to-current conversion stage, providing inherently linear operation. The current mode DACs directly generate current outputs that can be summed without conversion losses, thereby maintaining both high dynamic range and linearity simultaneously.
2Productivity
If voltage mode DACs with filters and active stages are used, then MAC operations can be performed, but power consumption increases
Solution Approach 1:
The patent extracts and removes the unnecessary voltage mode conversion stages and associated active filters from the system. By using current mode DACs that directly output currents, the design eliminates power-hungry voltage buffers and conversion circuits, achieving MAC operations with significantly reduced power consumption.
3Productivity
If voltage mode DACs with additional filters and active stages are used, then MAC operations can be performed, but device size increases
Solution Approach 1:
The patent removes the additional active stages and filter circuits that are required in voltage mode implementations. Current mode DACs integrate the multiplication and addition functions directly in the current summation node, eliminating the need for separate voltage buffers, active filters, and conversion stages, thereby reducing overall device area.
4Reliability
If current mode DACs are used to multiply input signal with current, then linearity is enhanced, but the system requires direct interface with non-volatile memory
Solution Approach 1:
The patent changes the operational parameter domain from voltage mode to current mode throughout the MAC unit. Current mode operation provides inherent linearity and naturally interfaces with non-volatile memory devices like MRAM that operate in the current domain, eliminating the need for voltage-to-current conversion stages and maintaining both linearity and interface compatibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves linearity and reduces power consumption and device size by eliminating the need for filters and drivers, while enabling efficient operations with non-volatile memory and improved performance in MAC operations.
Implementation Method 1
a first current mode digital-to-analog converter (DAC) configured to multiply an input signal with a first current having a first amplitude to generate a first signal
Implementation Method 2
a second current mode DAC configured to multiply the input signal with a second current having a second amplitude to generate a second signal
Implementation Method 3
a mixer configured to multiply the second signal with a clock signal to generate a third signal
Implementation Method 4
The third signal can be combined with the first signal via a current summing node to generate an output signal
Data Source
AI summary
Systems and methods to implement a multiply and accumulate (MAC) unit is described. In an example, a device can include a first current mode digital-to-analog converter (DAC) configured to multiply an input signal with a first current having a first amplitude to generate a first signal. The device can further include a second current mode DAC configured to multiply the input signal with a second current having a second amplitude to generate a second signal. The second amplitude can be less than the first amplitude. The device can further include a mixer configured to multiply the second signal with a clock signal to generate a third signal. The third signal can be combined with the first signal via a current summing node to generate an output signal. The output signal can be outputted to another device.