Four-Pin MOSFET Load Switch With Programmable Ramp Control

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Solution Overview

Problem

Integrated circuits with load switches require additional pins for features like adjustable slew and discharge rates, temperature control, over-current protection, and short circuit protection, which increases pin count and complexity.

Innovation Solution

A four-pin configuration for MOSFET load switches is implemented, utilizing a control pin, MOSFET drain pin, MOSFET source pin, and ground pin, with programmable ramp rate and adjustable discharge achieved without extra pins through voltage-controlled current sources and in-line discharge resistors, and over-temperature and over-current protection integrated into the circuitry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If additional pins are added for adjustable slew and discharge rates, temperature control, over-current protection, and short circuit protection, then the load switch provides full features, but the pin count and device complexity increase

Engineering Contradiction:

Improvefull featuresVSAvoidpin count

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The control pin serves multiple functions by accepting different voltage levels: it controls the MOSFET on/off state, adjusts slew rate through voltage-controlled current sources, and enables adjustable discharge rates. This multi-functionality eliminates the need for separate dedicated pins for each feature.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Multiple protection features (over-temperature, over-current, short circuit protection) and control functions (slew rate adjustment, discharge control) are merged into the existing four-pin configuration. The in-line discharge resistors and integrated protection circuitry combine multiple functions within the same pin structure.

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If voltage-controlled current sources and in-line discharge resistors are used, then programmable ramp rate and adjustable discharge are achieved without extra pins, but power consumption increases

Engineering Contradiction:

Improveprogrammable ramp rateVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The circuit uses voltage-controlled current sources that dynamically adjust the ramp rate based on the control pin voltage level. This dynamic control allows programmable ramp rates without requiring additional components, as the same circuit adapts its behavior based on input voltage conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The in-line discharge resistors provide automatic discharge functionality without requiring external control circuitry. The resistors are integrated directly into the load switch path, allowing the device to self-regulate discharge rates based on the control pin state without additional power-consuming control components.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS9065435B1Reduced pin full feature load switch

Publication Date: 2015.06.23 RENESAS DESIGN TECH INC

AI summary

A four pin integrated circuit MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) load switch is disclosed that provides full features including adjustable ramp time/rate, adjustable discharge time/rate, temperature control, over-current control, and short circuit protection. In some embodiments, the adjustable ramp is based on the voltage or current input into the integrated circuit.