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CN0349 Real and Ima reading error

Question asked by bwjm on Jan 10, 2018
Latest reply on Jan 10, 2018 by R.L

Hi, i am doubtful on my readings for the real and imag data. Will need help from you guys

 

These are my test setup

I am using the CN0349 eval kit.

 

Set AD5934 to standby mode:

address 0x80: write 0xB1 

address 0x81: write 0x08 

- 2.0 V p.p

- Gain 1

- External system clock

 

Initialize sweep:

address 0x80: write 0x11

 

Start sweep:

address 0x80: write 0x21

 

Start frequency:

address 0x82, x83, x84: write 0x418937

- 2.0kH

- with MCLK = 1Mhz at U6

 

Frequency increment:

address 0x85,x86: write 0x0000

- no increment

 

Number of Increment:

address 0x88,x89: write 0x0001

-number of increment = 1

 

Number of settling time:

address 0x8A, x8B: write 0x000C

 

Readings

Rcal1: Cal resistor = 100 ohm, RFB = 100ohms

Real: 7751

Imag: 60181

Mag: 61174.03

 

Rcal2: Cal resistor = 1kohm, RFB = 100ohms

Real: 806

Imag: 64980

Mag: 64985

 

I plotted the graph out and its downward line(attached pic), which gave me a negative gradient, do not tally with the Application notes of CN0349 which is a positive gradient. 

 

Could anyone spot what have i done wrong?

 

Thank you

 

Regards

Bryan

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