Vertical Metal Sensing Layout for Compact DC-DC Current Measurement
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Solution Overview
Problem
Existing current sensors for switched capacitor DC-DC converters face challenges in efficiently sensing input current and output voltage/current due to ripple currents, which require complex filtering and larger component sizes.
Innovation Solution
A current sensor design that includes a sense resistor coupled between first and second terminals to receive an input current, and an amplification circuit with a gain based on the resistance of a second resistor and the ratio of the sense resistor to a first resistor, allowing for ratiometric temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional current sensing methods are used in switched capacitor DC-DC converters, then accurate current measurement can be achieved, but the physical size of the low-pass filter becomes large
Solution Approach 1:
The patent changes the parameters of the low-pass filter by using a folded cascode operational amplifier with specific compensation techniques and resistor ratios to achieve the same filtering effect with reduced component values and smaller physical area
Solution Approach 2:
The patent transitions from traditional single-path current sensing to dual-path current sensing with differential amplification, adding a spatial dimension to the measurement approach that enables compact filter design while maintaining accuracy
2Object-generated harmful factors
If dual path switching is used to reduce ripple current, then ripple current is reduced, but the complexity of the circuit increases
Solution Approach 1:
The patent merges the current sensing function with the dual-path switching operation by using a single differential amplifier to sense currents from both paths simultaneously, combining multiple functions into one integrated circuit block that reduces overall complexity
Solution Approach 2:
The operational amplifier is designed to perform multiple functions: it amplifies the differential voltage from the sense resistors, filters high-frequency ripple components, and provides temperature compensation, making it a universal component that handles multiple tasks
3Stability of the object's composition
If ratiometric temperature compensation is implemented, then temperature stability is improved, but the number of resistors and circuit complexity increase
Solution Approach 1:
The patent uses parameter changes by selecting specific resistor ratios (R1/Rs and R2/Rs) that provide automatic temperature compensation through the ratiometric relationship, where the temperature coefficients of matched resistors cancel each other out, achieving stability without additional compensation circuits
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
The proposed solution effectively reduces the physical size of the low-pass filter by half, resulting in a more compact current sensor design that conserves area while maintaining accurate current sensing.
Implementation Method 1
a sense resistor coupled between first and second terminals to receive an input current from a power source
Implementation Method 2
an amplification circuit. The amplification circuit includes: an amplifier having inputs coupled to the first and second terminals across which the sense resistor is coupled, and an output at which a voltage representative of the input is produced; a first resistor coupled to at least one of the inputs of the amplifier; and a second resistor coupled to at least one of the inputs of the amplifier. A gain of the amplification circuit is based upon a resistance of the second resistor and a ratio of a resistance of the sense resistor to a resistance of the first resistor
Implementation Method 3
The first resistor and the sense resistor are formed from same materials in a same substrate and arranged in a ratiometric relationship such that the first resistor and sense resistor change temperature substantially equally during operation and such that the first resistor and sense resistor vary substantially equally in resistance over temperature
Data Source
Figure 1~2
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Figure 7~9
AI summary
In a DC-DC converter (200'), a layout is designed to enable utilization of the conductive trace connecting the converter output node (N2) to an output bump (BB1, BB2) at which the load (RL, CL) is attached as a sense resistor (Rs). The layout forces the output current down into lower metallization levels (201) of an interconnect layer reaching the converter output node (N2) before the output current flows up into this conductive trace (212) and out through the output bump (BB1, BB2). The conductive trace (212) includes resistive pillars connected in parallel or series between the lower metallization levels (201) and a top metallization layer (207c) of the conductive trace (212), with these resistive pillars being substantially greater in resistance than the lower metallization levels (201) and the top metallization layer (207c) of the conductive trace (212).