Adjust amplitude of AD9958 output wave


     I am using the AD9958 to generate two signal at the same frequency. Channel 0 is modulated in FSK mode with a low frequency square wave applied on pin 42 (P2 used as CH0 two-level modulation input). Channel 1 is not modulated

     Now, I want to adjust the output amplitude independently on both channels.

     I make some coarse adjustment of these amplitude with variable "DAC full-scale current control" data written in CFR's. Both channels works independently: after addressing correct "Channel enable" bits in CSR, I got variation on 1-2-4-8 scales.

     I try to make fine adjustments with variable "Amplitude scale factor" data written in ACR's.but the amplitude always remain max value.the Rset = 1.91kΩ,the out pin connect to AVDD(1.8V) through 50Ω.

     Thanks for help

  • Hi,

    I think enabling manual mode would make your adjustments to take effect.

    "Manual mode allows the user to directly control the output amplitude by manually writing to the amplitude scale factor value in the ACR (Register 0x06). Manual mode is enabled by setting ACR[12] = 1 and ACR[11] = 0"

    Best regards,