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What would cause the CP to go out of range after calibration?

Question asked by achernock on Jan 23, 2018
Latest reply on Jan 23, 2018 by sripad

My customer is using an AD9361 transceiver on an FMCOMMS5 eval board.  For various reasons, they’re writing their own driver for the device, but want to initialize the device in essentially the same way as Analog’s driver.

 

So far, their driver is able to complete the calibration of the baseband PLL and the Rx RF charge pump.  Then they try to do the Rx RF VCO calibration, but it never completes, and reg 0x247 bit 7 indicates that the charge pump is overrange.

 

I’ve attached a list of the register writes and reads that they're doing, and the header code they're using.  They defined the functions atd_write and atd_read for writing and reading to the device regs over SPI.  The SPI interface is functioning without any problems as far as they can see. 

 

Do you have any thoughts on what would cause the overrange and the failure of the RF VCO cal?  Any advice would be appreciated.

 

The first two calibrations return the following results.

 

BBPLL VCO cal:                  reg 0x05E = 0x80, so BBPLL VCO cal is good

RF synth CP cal:                 reg 0x244 = 0xA8, so CP cal is done and valid, cal word = 8

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