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Passive Electrical Detent for External Power Supply Modes

IP.com Disclosure Number: IPCOM000237633D
Publication Date: 2014-Jun-27
Document File: 5 page(s) / 114K

Publishing Venue

The IP.com Prior Art Database

Related People

Mark Pude: INVENTOR

Abstract

This publication describes a passive electrical detent switch for power supplies that may or may not be provided by an external source. In this context, an electrical detent is in some ways analogous to the well-known mechanical detent that resists or arrests mechanical movement to some extent. Similarly, a passive electrical detent holds a voltage at a certain level until overridden or disabled. In the case that the supply is provided externally, the external supply may override and disable the detent and drive the supply to its desired value. In the case that the supply is generated internally, the detent will hold the supply in a known and driven state until the active shorting switch can be enabled.

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Passive Electrical Detent for External Power Supply Modes

Passive Electrical Detent for External Power Supply Modes


1. Inventor: Mark Pude

2. Synaptics Incorporated, San Jose, CA, USA


3. Short Summary

V1-V2 > VT, Detent = 0 V1-V2 < VT, Detent = 0 Otherwise, Detent = 1

Enable

Short

Figure 1. Active short switch and proposed passive electrical detent short switch

This publication describes a passive electrical detent switch for power supplies that may or may not be provided by an external source. In this context, an electrical detent is in some ways analogous to the well-known mechanical detent that resists or arrests mechanical movement to some extent. Similarly, a passive electrical detent holds a voltage at a certain level until overridden or disabled. In the case that the supply is provided externally, the external supply may override and disable the detent and drive the supply to its desired value. In the case that the supply is generated internally, the detent will hold the supply in a known and driven state until the active shorting switch can be enabled.


4. Some Problems Solved

Touch Display Driver Integrated Circuit (TDDI) is an integrated circuit that is configured to both update a display and capacitive sensing on the display. There are several power supplies relevant to TDDI operation that are generated internally on chip. Often, they are disabled by shorting one supply to another (e.g. VDDA, a power supply supplied internally or externally, may be shorted to VDDDC, a power supply supplied externally). This behavior is defined by the design and reset behavior of the part. If a power supply like VDDA is provided externally, however, the internal disable state may be in Copyright © 2014 Synaptics Incorporated, All Rights Reserved.

Page: 1 of 5

Information contained in this publication is provided as-is, with no express or implied warranties, including any warranty of merchantability, fitness for any particular purpose, or non-infringement. Synaptics Incorporated assumes no liability whatsoever for any use of the information contained herein, including any liability for intellectual property infringement. This publication conveys no express or implied licenses to any intellectual property rights belonging to Synaptics or any other party. Synaptics may, from time to time and at its sole option, update the information contained herein without notice.

Mark Pude

Supply 1

Main switch

  Supply Comparator

V1

V2

Detent switch

Detent

Supply 2


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Passive Electrical Detent for External Power Supply Modes

contention with the Integrated Circuit's (IC) disable state (e.g. an external supply might short VDDA to GND while disabled, in contention with the IC driving it to VDDDC). This means that until the IC knows if it is in external or internal mode, no assumptions should be made about the disable state of supplies that may be externally provided and the supplies should be undriven internally. In the case that the application in...