AD9835 FSYNC voltage level

I'm designing a signal generator using a AD9835. I'm interfacing it via a PIC16F88, using these pins for the SPI bus: SDO=pinB2, SCK=pinB4, SS=pinB5. I connect those pins to the correspondent pins in the AD9835: pinB2->SDATA, pinB4->SCLK, pinB5->FSYNC.

I tried with the hardware and the software version of the SPI protocol (this PIC has SPI dedicated hardware), so the PIC's pins that I used can be changed.

I'm also using a 20MHz crystal for the PIC's clock and a 50MHz crystal oscillator for the AD9835.

The SDATA and the SCLK lines are working correctly, but I found that the FSYNC high voltage is only 1V, where it should be 5V as in the others. I tried disconnecting the pinB5 from the circuit and reading the values directly from it and in this case it works correctly, 5V.

Even knowing that a SPI bus doesn't need pull-up resistors, I tried nonetheless, but the result was the same, 1V.

What could be possibly happening in with the AD9835 that it forces the high voltage to 1V only?

Parents Reply Children
No Data