Power On Reset Circuit Current Offset Stabilization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power on reset (POR) circuits exhibit a wide spread in operational threshold due to process corner and temperature variations, leading to inconsistent Vana voltage at which the POR output signal is asserted.
Innovation Solution
A POR circuit design incorporating a current summing junction with a bandgap current source and a variable current source, where the bandgap current is constant above a first voltage threshold, and the variable current varies with supply voltage, offsetting each other at the current summing junction to stabilize the POR output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional POR circuit uses MOSFET threshold voltages to determine operational threshold, then the circuit structure is simple, but the operational threshold exhibits wide spread with process corner and temperature
Solution Approach 1:
The patent changes the fundamental parameter used for threshold determination from MOSFET voltage thresholds to a current-based comparison mechanism. By using a bandgap reference voltage to generate a stable reference current and comparing it with a voltage-dependent current at the summing junction, the circuit achieves temperature and process-independent operation. This parameter change from voltage-threshold-based to current-comparison-based operation resolves the contradiction between simple structure and reliable consistent threshold.
2Ease of manufacture
If a POR circuit uses MOSFET threshold voltages for operation, then the implementation is straightforward, but the POR output signal assertion voltage varies widely across process and temperature
Solution Approach 1:
The patent introduces a bandgap reference voltage as an intermediary element that mediates between the supply voltage and the threshold determination mechanism. The bandgap reference, being temperature and process independent, generates a stable reference current that serves as a consistent comparison基准. This intermediary reference current allows the circuit to maintain precise and consistent POR assertion voltage across varying process and temperature conditions while remaining manufacturable.
3Device complexity
If a POR circuit relies on transistor threshold voltages, then the design is simple, but the operational threshold lacks precision and consistency
Solution Approach 1:
The patent substitutes the mechanical/electrical property of MOSFET threshold voltages with an electromagnetic field-based bandgap reference voltage mechanism. The bandgap reference operates on the principle of compensating for temperature effects through the combination of positive temperature coefficient (PTAT) and negative temperature coefficient (NTAT) components, creating a voltage that is inherently immune to temperature and process variations. This substitution replaces the imprecise transistor threshold mechanism with a precision reference system.
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 achieves a consistent POR output signal by stabilizing the operational threshold across different temperature and process corners, ensuring the POR output signal is asserted at a precise Vana voltage, as demonstrated by the simulated performance data showing close high and low transition voltage levels across temperature and process extremes.
Implementation Method 1
a bandgap current source circuit configured to generate a bandgap current applied to the current summing junction, wherein a magnitude the bandgap current is constant for a supply voltage which exceeds a first voltage threshold
Implementation Method 2
the variable current is offset against the bandgap current at the current summing junction
Data Source
AI summary
A Schmitt trigger circuit having an input coupled to a current summing junction. A trickle current source generates a trickle current applied to the current summing junction. A bandgap current source generates a bandgap current applied to the current summing junction (wherein the bandgap current is fixed when a supply voltage exceeds a threshold). A variable current source generates a variable current applied to the current summing junction (wherein the variable current varies dependent on the supply voltage). At the current summing junction, the variable current is offset against the trickle and bandgap currents with respect to generating a voltage that is sensed at the Schmitt trigger circuit input.