Negative-Input Load Switch Using Pin-Reused Level Shifting

Solution Overview

Problem

Conventional integrated load switches require additional circuitry and pins for negative input applications, increasing cost and complexity.

Innovation Solution

An integrated circuit with a load switch that uses a negative input voltage, employing control circuitry with a level shifter and slew rate controller to manage the enable signal, utilizing the ground pin as a positive supply rail and the input pin as an internal ground, thereby eliminating the need for extra pins or circuitry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional integrated load switches use both positive and negative supplies for negative input applications, then the load switch can operate with negative inputs, but additional pins and internal circuitry are required, increasing cost and complexity

Engineering Contradiction:

Improvecapability to handle negative inputsVSAvoidnumber of pins and internal circuitry

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The control circuitry is designed to perform multiple functions using the same pins. The ground pin serves dual purposes as both a ground reference and a positive supply rail for the control circuitry, while the input pin serves as both the negative voltage input and an internal ground reference. This multi-functionality eliminates the need for separate dedicated pins for positive and negative supplies, reducing pin count and device complexity while maintaining the capability to handle negative inputs

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If conventional integrated load switches use both positive and negative supplies, then negative input operation is supported, but the cost increases due to extra pins and circuitry

Engineering Contradiction:

Improvesupport for negative input applicationsVSAvoidmanufacturing cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The control circuitry is designed to perform multiple functions using the same pins. The ground pin serves dual purposes as both a ground reference and a positive supply rail for the control circuitry, while the input pin serves as both the negative voltage input and an internal ground reference. This multi-functionality eliminates the need for separate dedicated pins for positive and negative supplies, reducing pin count and device complexity while maintaining the capability to handle negative inputs

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8854097B2Load switch

Publication Date: 2014.10.07 TEXAS INSTRUMENTS INC

AI summary

An IC generally comprises enable pin, ground pin, input pin, output pin, load switch, control circuitry, and level shifter. Load switch is coupled between the input pin and output pin and receives a negative voltage through the input pin. The control circuitry is coupled to the enable pin, the ground pin, and the load switch and controls the load switch and uses ground pin as positive supply rail and input pin as an internal ground. Voltage applied to the input terminal is negative, enabling pulling of the gate of a transistor of a level shifter to ground turns transistor as “on,” enabling a negative output signal to be provided through output pin VOUT. Therefore, the output signal (at output pin VOUT) can be ground (applied to the ground pin GND) when the transistor is “off” and can be the negative voltage (applied to the input pin VIN) when transistor is “on.”