Cypress AutoStore STK17T88 Montage- und Bedienungsanleitung

November 06, 2008 Document # 001-49947 Revision ** 1

Undershoot Effect in RTC Circuit

of 0.25μnvSRAM

Application Note Abstract

This application note describes the undershoot effect in the RTC circuit of the 256K and 1M nvSRAM in 0.25μtechnology. The

part numbers affected are CY14B256K/STK17T88 and CY14B101K/STK17TA8.

Introduction

Under certain noise conditions, the Real Time Clock (RTC)

circuit of CY14BXXXK/STK17TX8 can be disturbed to the

point that the oscillator circuit stops.

Undershoot in Application

The RTC devices in 0.25μspecify in the data sheet that

inputs may not undershoot by more than –0.5V. This is diffi-

cult to achieve in systems where signal fall times are fast (1

to 3 ns). As a result of these fast fall times, signal undershoot

greater than –0.5V is quite common.

Signal undershoot greater than –0.5V causes the ESD

diodes on the device inputs to conduct current. This current

travels through the substrate until it reaches collection points

(guard bands with substrate contacts). However, as this cur-

rent flows within the substrate, it adds noise to the overall

noise floor on the device.

Figure 1. Signal Undershoot

Effect on RTC Oscillator

The RTC oscillator circuit, which is embedded on the 256K

and 1M nvSRAM family is designed to be a very low power

circuit. To achieve this low power operation, the automatic

gain circuit of the oscillator is designed to operate on very

small currents (nano-Amperes). This makes the gain circuit

sensitive to on-chip noise, which in turn makes the RTC oscil-

lator circuit very sensitive to substrate currents caused by sig-

nal undershoot.

There have been reports of the oscillator stopping in some

customer systems. Investigation showed that these systems

all had a significant amount of undershoot. Correcting the

undershoot on the input pins corrected the problem. The

address pins A

-A

and data pin DQ

are located in the area

of the RTC oscillator circuit. Undershoot on these address

pins has the greatest effect on the RTC circuit operation. It is

recommended that customers experiencing similar problems

investigate and correct undershoot issues.

Recommendation

Undershoot can be reduced by adding a Schottky diode (V

0.4V with I

at 100 mA) connected with the anode at ground

and cathode on the signal line as close to the device pin as

possible. Layout must route the signals to connect to the

diode first then the pin if possible. The anode to ground

should go directly to the ground plane. The only signals that

require this treatment are A

, A

, and DQ

. A scope

must be used to confirm controlled undershoot as some fast

edge rates may need more effective termination. It is critical

that the voltage does not go below 0.6V as substrate currents

begin to flow.

AN49947

Associated Part Family: CY14BXXXK/STK17TX8

GET FREE SAMPLES HERE

EDS DIODE

CONDUCTION

-2V

3.3V

Conduction

ESD Diode

[+] Feedback

AN49947

Cypress Semiconductor

198 Champion Court

San Jose, CA 95134-1709

Phone: 408-943-2600

Fax: 408-943-4730

http://www.cypress.com

assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under

patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or safety applications,

unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as critical components in

life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress products

in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges.

This Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide

patentprotection(UnitedStatesandforeign), UnitedStatescopyright laws and internationaltreatyprovisions.Cypresshereby grantstolicenseeapersonal,

non-exclusive, non-transferable license to copy, use, modify, create derivative works of, and compile the Cypress Source Code and derivative works for

the sole purpose of creating custom software and or firmware in support of licensee product to be used only in conjunction with a Cypress integrated circuit

asspecifiedintheapplicableagreement.Any reproduction, modification, translation,compilation,or representation of this SourceCodeexcept asspecified

above is prohibited without the express written permission of Cypress.

Disclaimer: CYPRESS MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT

LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the right to

make changes without further notice to the materials described herein. Cypress does not assume any liability arising out of the application or use of any

product or circuit described herein. Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or

failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress' product in a life-support systems application implies

that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges.

Use may be limited by and subject to the applicable Cypress software license agreement.

November 06, 2008 Document # 001-49947 Revision ** 2

Document History

All trademarks or registered trademarks referenced herein are the property of their respective owners.

Document Title: Undershoot Effect in RTC Circuit of 0.25μ nvSRAM

Document Number: 001-49947

Revision ECN No. Orig. of

Change Submission

Date Description of Change

** 2606848 NXR 11/13/08 New application note

[+] Feedback

Andere Handbücher für AutoStore STK17T88

Dieses Handbuch passt für folgende Modelle

Inhaltsverzeichnis

Andere Cypress Computerhardware Handbücher

Cypress

Cypress UNIVERSAL CAPSENSE CY3280-BMM Bedienungsanleitung

Cypress

Cypress PSoC FirstTouch CY3270 Bedienungsanleitung

Cypress

Cypress CY62128B Bedienungsanleitung

Cypress

Cypress MB9B160R Series Bedienungsanleitung

Cypress

Cypress CY8CKIT-036 Bedienungsanleitung

Cypress

Cypress CY62138EV30 Bedienungsanleitung

Cypress

Cypress CY91590 Series Bedienungsanleitung

Cypress

Cypress CY62136VN Bedienungsanleitung

Cypress

Cypress CY8CKIT-038 Bedienungsanleitung

Cypress

Cypress CY4541 EZ-PD CCG4 Evaluation Kit Bedienungsanleitung

Cypress

Cypress CY8C22113 Bedienungsanleitung

Cypress

Cypress CY14B104L Bedienungsanleitung

Cypress

Cypress PSoC DESIGNER ImageCraft M8C Bedienungsanleitung

Cypress

Cypress PSoC CY8CKIT-029A Bedienungsanleitung

Cypress

Cypress CMIR-44 Bedienungsanleitung

Cypress

Cypress CY3240-I2USB Bedienungsanleitung

Cypress

Cypress CY8CKIT-035 Bedienungsanleitung

Cypress

Cypress 001-07160 Bedienungsanleitung

Cypress

Cypress CY62167DV18 Bedienungsanleitung

Cypress

Cypress MB2198-01 Bedienungsanleitung

Cypress

Cypress EZ-OTG CY7C67200 Bedienungsanleitung

Cypress

Cypress CY8CKIT-031 Bedienungsanleitung

Cypress

Cypress EZ-PD CCG3 Bedienungsanleitung

Cypress

Cypress AutoStore STK17T88 Bedienungsanleitung

Beliebte Computerhardware Handbücher anderer Marken

EMC2

EMC2 VNX Series Betriebsanleitung

Panasonic

Panasonic DV0PM20105 Bedienungsanleitung

Mitsubishi Electric

Mitsubishi Electric Q81BD-J61BT11 Bedienungsanleitung

Gigabyte

Gigabyte B660M DS3H AX DDR4 Bedienungsanleitung

Raidon

Raidon iT2300 Bedienungsanleitung

National Instruments

National Instruments PXI-8186 Bedienungsanleitung

Hauppauge

Hauppauge WinTV-HVR-2250 Bedienungsanleitung

Kontron

Kontron CP6002 Bedienungsanleitung

Manhattan

Manhattan 702843 Bedienungsanleitung

Aphex

Aphex 230 Bedienungsanleitung

AMD

AMD Phenom II Betriebshandbuch

Intel

Intel NUC 12 Pro Bedienungsanleitung

dbx

dbx Zone Pro 1260 Bedienungsanleitung

Galaxy

Galaxy GHDX2-2430S-24F4D Bedienungsanleitung

Intel

Intel AXXRMFBU4 Bedienungsanleitung

Kontron

Kontron DIMM-PC/MD Bedienungsanleitung

ST X-NUCLEO-SAFEA1B Betriebsanleitung

STEINWAY LYNGDORF

STEINWAY LYNGDORF SP-1 Bedienungsanleitung