Hi,
I am currently powering the VCC_VCO pin from the internal LDO (pins 6 and 7 connected), but I am supplying the VCC_LDO pin from a 5V regulator (LT3045). I realized after the board was fabricated that I should have either supplied the output of the external regulator to both VCC_LDO and VCC_VCO (tying pin 7 to pin 8 and disabling the internal LDO) OR connected the VCC_LDO to the 6V unregulated supply.
Can I just short pins 6, 7, and 8 together and power them from the external regulator? Will this damage the device? Should the LDO be enabled or disabled in that case? What about the fact that the LDO is enabled on startup?
Also, with 5.0Vdc on VCC_LDO, I am getting 4.46V from the LDO and to the VCC_VCO pin. Is this normal? The data sheet says that VCC_VCO should be between 4.75 and 5.25 volts.
In any case, the output of my N-Divider/2 MUXOUT setting is around 13.5-13.7 MHz, and will not lock to my 10 MHz reference signal.
Thanks,
Dr. Jim Aarestad
University of New Mexico
