AD9552 Automatic VCO Calibration

Question

I have found that the AD9552 PCBZ eval board appears to not be enacting automatic VCO calibration, contrary to the datasheet. When I have the board configured for manual control through the dip switches (configured to use a 10 MHz reference to generate a 156.25 MHz output, according to the manual) it initially generates the wrong frequency (typically ~152 MHz as measured by my scope). If I issue a reset by asserting/deasserting the DIP switch on S2, it begins generating the correct frequency. According to the datasheet, the VCO calibration routine should run on power-up. I suspect that it isn't, which is causing the poor frequency accuracy, and it only runs after issuing the reset manually. Is there a direct method for me to test this suspicion? 
 Additionally, when I configure the board for PC Control, every time I power on the board and read Register 0x0E, it reads back as b'01110 1 00, indicating that SPI control of VCO calibration is enabled. Is there a way to test whether the default register map setting of address 0x0E has somehow been changed? I don't see any documentation on the "USB EEPROM Enable" feature, is it possible that this setting is being loaded from EEPROM?

pminc48 · Accepted Answer

Hi, 
 
 This is from the data sheet rev E, page 17: 
 
 The eval board comes with an installed 26MHz crystal resonator. You seem to want to use a 10MHz reference clock. Please make sure that when you power up the board, the 10MHz clock is applied. The schematic of the REF pin on the eval board is that of a dc coupled input. So you need to apply a 10MHz CMOS clock that has at least 1.62V high level and max 0.52V low level. 
 If you want, please send me the stp configuration file you use, so I can play with it in the lab myself. 
 The register 0x0E being 0x74: this is not the default value (0x70), so this means the register is changed when the chip is configured. The default values of the registers are in the Register Map section of the data sheet, page 23. 
 Not clear to me what "USB EEPROM enable" feature you are referring to. Please point me in the right direction 
 Petre)

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AD9552 Automatic VCO Calibration