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AD9833 - Not oscillating 300mv O/P

Question asked by jimbob on Sep 8, 2016
Latest reply on Sep 20, 2016 by jimbob

Hi,

 

I've pretty much copied the UG-272 schematic and made a board up, but when testing I just get a static 300mV output.

On power up there's 300mV, drops down to about 100mV, then down to 0V and back to 300mV.

I've followed the AN-1070 and followed their basic example to create a 400Hz sine wave. I'm using CCS compiler on a dspic33, below are some snip-its:

 

// SPI Config

#USE SPI (DI=PIN_F7, DO=PIN_F8, CLK=PIN_F6, ENABLE=PIN_B2, MSB_FIRST, STREAM=AD9833, ENABLE_ACTIVE=0, MODE=1, BAUD=400000, BITS=16) 

 

// setup sinewave

spi_xfer(AD9833, 0x2100, 16);
delay_ms(2000);
spi_xfer(AD9833, 0x50C7, 16);
delay_ms(200);
spi_xfer(AD9833, 0x4000, 16);
delay_ms(200);
spi_xfer(AD9833, 0xC000, 16);
delay_ms(200);
spi_xfer(AD9833, 0x2000, 16);

 

Here's my schematic, my oscillator is 16MHz so I'm not expecting to get 400Hz as per the app note. Oscillator running fine, 3V3 present and I've examined the SPI data which is correct, the only thing left to try is replace the IC, any ideas what's wrong anyone please?

 

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