The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> Help me for problems with HEF4751V https://designers-guide.org/forum/YaBB.pl?num=1078209053 Message started by Ivan Dachev on Mar 1st, 2004, 10:30pm |
Title: Help me for problems with HEF4751V Post by Ivan Dachev on Mar 1st, 2004, 10:30pm Hello, I have one problem using HEF4750V and HEF4751V HEF4750V is Frequency synthesizer form Philips http://www.semiconductors.philips.com/acrobat/datasheets/HEF4750V_CNV_3.pdf HEF4751V is Universal divider form Philips http://www.semiconductors.philips.com/acrobat/datasheets/HEF4751V_CNV_3.pdf First at all I want to say that I have working synthesizer with above schemes. I make it working on radio bands 1.8Mhz 3.5Mhz 7Mhz ... 28.5Mhz The channels are to 1Khz and I using DAC to make sub channels to 10Hz It works fine but has some errors. I control the universal divider HEF4751V and DAC with PIC16F84. In this PLL synthesizer the value of N, by which the output frequency is divided in order to compare it with the reference frequency(1Khz) is construct by this formula N = A - B or N = A - B + 10^6 (if A - B < 0) A and B is numbers which can be programmed in HEF4751V In my synthesizer I use only A number. I put for A number this 35.600Mhz + 3.5Mhz = 39.100Mhz for my VCO. in this situation N = 39.100 - (B=0) THE PROBLEM: I read in some other design of such synthesizer that I can program B number in such way that I can just put in A direct frequency as 3.5Mhz and N will be 39.100! By my calculation B must be this B = A - N + 10^6 = 3 500 - 39 100 + 10^6 = 964 400 Problem is that when I put this B = 964 400 in HEF4751V my PLL is locket but the channels do not change :( for example on 1.8 3.5 and 7Mhz it locks near on 40.500Mhz I change A but it stay on one frequency Has some one do such synthesizer and can help to me with above problem? |
The Designer's Guide Community Forum » Powered by YaBB 2.2.2! YaBB © 2000-2008. All Rights Reserved. |