The following document contains information on Cypress products.

Transcription

1 The following document contains information on Cypress products.

2 Spread S pectrum Clock Generator SSCG SSCG application for 5V system

3 All Rights Reserved. The contents of this document are subject to change without notice. Customers are advised to consult with FUJITSU sales representatives before ordering. The information, such as descriptions of function and application circuit examples, in this document are presented solely for the purpose of reference to show examples of operations and uses of Fujitsu semiconductor device; Fujitsu does not warrant proper operation of the device with respect to use based on such information. When you develop equipment incorporating the device based on such information, you must assume any responsibility arising out of such use of the information. Fujitsu assumes no liability for any damages whatsoever arising out of the use of the information. Any information in this document, including descriptions of function and schematic diagrams, shall not be construed as license of the use or exercise of any intellectual property right, such as patent right or copyright, or any other right of Fujitsu or any third party or does Fujitsu warrant non-infringement of any third-party s intellectual property right or other right by using such information. Fujitsu assumes no liability for any infringement of the intellectual property rights or other rights of third parties which would result from the use of information contained herein. The products described in this document are designed, developed and manufactured as contemplated for general use, including without limitation, ordinary industrial use, general office use, personal use, and household use, but are not designed, developed and manufactured as contemplated (1) for use accompanying fatal risks or dangers that, unless extremely high safety is secured, could have a serious effect to the public, and could lead directly to death, personal injury, severe physical damage or other loss (i.e., nuclear reaction control in nuclear facility, aircraft flight control, air traffic control, mass transport control, medical life support system, missile launch control in weapon system), or (2) for use requiring extremely high reliability (i.e., submersible repeater and artificial satellite). Please note that Fujitsu will not be liable against you and/or any third party for any claims or damages arising in connection with above-mentioned uses of the products. Any semiconductor devices have an inherent chance of failure. You must protect against injury, damage or loss from such failures by incorporating safety design measures into your facility and equipment such as redundancy, fire protection, and prevention of over-current levels and other abnormal operating conditions. If any products described in this document represent goods or technologies subject to certain restrictions on export under the Foreign Exchange and Foreign Trade Law of Japan, the prior authorization by Japanese government will be required for export of those products from Japan. The company names and brand names herein are the trademarks or registered trademarks of their respective owners. Copyright 2009 FUJITSU MICRELECTRONICS LIMITED all rights reserved 1

4 Revision History Rev Date Remark /5/18 First Edition 2

5 Subject Revision History...2 Subject Introduction Application example to 5V system...5 3

6 1 Introduction The document shows the example of proposal to 5V system using 3V SSCG. (SSCG : Spread Spectrum Clock Generator). Our SSCG p roduct lineup is mainly 3V operat ion. So 5V system cannot use 3V SSC directly. So we propose to 5V system using 3V SSCG and some circuit. G 4

7 2 Application example to 5V system FUJITSU SSCG operates with not only a gener al 3-terminal regulator bu t also a simple regulator because its power consumption is a little. The amplitude of the clock output from SSCG becomes about 3V. The threshold voltage is about 1.4V in most 5V interfaces. So, 3V SSCG can be used in 5V interface in many cases. (Please confirm the specification of the device to which the clock output of SSCG is input) Moreover, if the amplitude of the clock out put becomes small, a unnecessary radiatio n noise becomes small. Th is is because the val ue of an unnecessary radiatio n is in inverse proportion to the second power of the voltage. Because of above 2-point, It is more advantageous for the EMI decrease to use regulat or and FUJITSU SSCG than 5V operation SSCG. 5V Regulator SSCG 3V 3V swing 5V operation LSI Vth=1.4V Figure 1. Circuit example of 5V system using 3V SSCG and regulator 5

8 Figure 2. shows the circuit example using a s ilicon diode as a simple regulator. A silicon diode is used for dropping 5V to 3V. R1 is in serted because the excess voltage is not impresse d to SSCG when the po wer supply is turned on. (Ple ase confirm whether the SSCG powe r supply val ue is a range of recommended operation voltage (3.0V to 3.6V) or not. C1 and C 2 are b ypass cap acitors for st able power sup ply. The value of the figure is recommended one. Please examine the best value by your system. Silicon diode VDD 5V SSCG C1 0.01µF C2 10µF R1 A range of VSS kω- 10kΩ Figure 2. Circuit example of 5V system using 3V SSCG and silicon diode 6

9 Figure 3. shows the circuit ex ample using a Light emitting di ode(led) as a silicon diode. A LED is used for dropping 5V to 3V. It is suitable to use the L ED that has 1.6V to 1.8V volt age drop for the sys tem.(about the color, red, orange, yellow or green is suitable.) Blue or white color LED cannot use because its drop voltage is over 3.0 V. LED VDD 5V SSCG C1 0.01µF C2 10µF R1 A range of VSS kω- 10kΩ Figure 3. Circuit example of 5V system using 3V SSCG and LED 7

10 Figure 4. shows the circuit example using a Zener diode as a silicon diode. Zener diode has the temperature dependence. If you use zener diode, please confirm the operation temperature range of system and zener diode. R1 5V 3V Zener VDD C1 C2 SSCG 0.01µF 10µF VSS Figure 4. Circuit example of 5V system using 3V SSCG and Zener diode - End - 8