Adaptive Body Bias in Voltage Regulators for Latch-Up Control
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Solution Overview
Problem
Existing voltage regulators, such as low drop-out (LDO) regulators, face inefficiencies due to limitations in gate-to-source voltage and potential latch-up conditions, especially when combined with switching regulators in battery-powered devices.
Innovation Solution
A voltage regulator design incorporating a p-type metal oxide semiconductor field effect transistor (PMOS) with a back-gate biased by a complementary to absolute temperature (CTAT) current generator, which adjusts the threshold voltage to improve efficiency and reduce latch-up risks, using a trimmable resistor and CTAT current to manage back-gate biasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional LDO regulator uses a standard gate-to-source voltage configuration, then the circuit is simple, but the load current capacity is limited and voltage headroom is reduced
Solution Approach 1:
The patent introduces a back-gate biasing dimension to the conventional LDO regulator by adding a CTAT current generator that applies a voltage to the back-gate of the pass transistor. This additional control dimension allows independent adjustment of threshold voltage without affecting the main gate-to-source voltage, thereby increasing load current capacity and voltage headroom while maintaining circuit simplicity
Solution Approach 2:
The patent changes the electrical parameters of the pass transistor by introducing a back-gate bias voltage generated by the CTAT current generator. This parameter change dynamically adjusts the threshold voltage of the pass transistor, enabling higher load current capacity and improved voltage headroom without significantly increasing overall circuit complexity
2Productivity
If the gate-to-source voltage is increased to improve load current capacity, then productivity improves, but the risk of latch-up conditions increases
Solution Approach 1:
The patent changes the threshold voltage parameter of the pass transistor by applying a back-gate bias voltage from the CTAT current generator. This allows the transistor to operate at higher current densities without exceeding the safe gate-to-source voltage limits, thereby increasing load current capacity while maintaining reliability and preventing latch-up conditions
Solution Approach 2:
The patent segments the voltage control function into two independent parts: the main gate-to-source voltage control for basic operation and the back-gate bias voltage control for threshold voltage adjustment. This segmentation allows optimization of load current capacity through back-gate biasing without compromising reliability, as each control path can be independently optimized
3Use of energy by moving object
If a switching regulator is combined with an LDO regulator to improve efficiency, then energy efficiency improves, but the gate-to-source voltage limitation becomes more critical
Solution Approach 1:
The patent changes the threshold voltage parameter of the pass transistor through back-gate biasing, which effectively increases the available gate-to-source voltage for driving the transistor. This allows the LDO regulator to operate efficiently in combination with a switching regulator, maintaining high energy efficiency while overcoming the gate-to-source voltage limitation through parameter adjustment
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
Enhances load current capacity and voltage headroom while reducing latch-up potential, thereby improving efficiency and performance in battery-powered devices.
Implementation Method 1
A CTAT current generator circuit is coupled to the resistor and configured to generate a CTAT current to bias the first resistor
Implementation Method 2
the threshold voltage of the drive transistor can be lowered. Lowering the drive transistor's threshold voltage permits the drive transistor to be turned on with a lower gate-to-source voltage
Data Source
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AI summary
In described examples, a voltage regulator (100) includes a pass transistor (108) coupled to an input voltage node (VTNB) and an output voltage node (109). The voltage regulator (100) also includes a drive transistor (102) coupled to a control input of the pass transistor (108) and a first resistor (RSB) coupled between a source and a back gate of the drive transistor (102). The voltage regulator (100) further includes a complementary to absolute temperature (CTAT) current generator (110) circuit coupled to the first resistor (RSB) and configured to generate a CTAT current to bias the first resistor (RSB).