Questions about AD9914 Digital ramp modulation(linear sweep)

Hi all,       

I would like to use AD9914 to achieve the output Sawtooth frequency rang 100MHz to 600MHz, I am not sure whether to configure pins 25, 26, 27 [PS0, PS1, PS2]. In other words,I am not sure whether to configure Single Tone Register.

I use external 100MHz crystal oscillator to multiply to 2.5GHz by internal PLL. Here is how I configure the register: CFR1(0x01,0x03,0x00,0x00)、CFR2(0x00,0x0C,0x28,0x00)、CFR3(0x00,0x44,0x11,0x50)、Digital Ramp Lower Limit Register(0x0A,0x3D,0x70,0xA4)、 Digital Ramp Upper Limit Register(0x3D,0x70,0xA3,0xD7)、Rising Digital Ramp Step Size Register(0x00,0x5E,0x5F,0x31)、Digital Ramp Rate Register(0x00,0x00,0x00,0x0F).Are these configurations correct

Here is how I configure the external pins: pin 63(DRCTL) is configured as high level, and pin 64(DRHOLD) is configured as low level.  In addition to the above configuration, do I need to configure any external pins?

Thank you.

Best,

Kedda

  • 0
    •  Analog Employees 
    on Nov 9, 2020 3:21 AM 23 days ago

    Hi Guet,

    I apologize for the late reply. If you are starting out with the part or evaluation board, I recommend to use the Single Tone Register and just see if you can successfully have an output. For sanity check, you can also use the SYNC_CLK to verify if your part have a proper clock signal propagating into the system. Where you able to successfully out a single tone output. Is that the case? Were you using an evaluation board in this?

    Regarding the digital ramp generation, I'd like you to refer to page 25 of the data sheet, figure 38. This comprehensively shows the function of the pins. DRCTL pinsa are used to set the direction of the ramp. I advise to connect them to a GPIO pin from your microcontroller for design flexibility, meaning, you can ramp up or down depending on the logic of your microcontroller.

    Thanks

    Louijie