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AD9910 has no signal out

Question asked by chang on Mar 20, 2018
Latest reply on Mar 22, 2018 by chang

hello everyone!in my design i use ad9910 to generate 200mhz signal .i used recomanded cricuit in the datesheet .i supply an external crystal oscillator at 20mhz.with the pll in the dds to get 1ghz reference.after power on.there is a 250mhz signal from the pin  sync_clk.a 20mhz signal from the pin refer_clkout.and the pin pll_lock has a high level looks work well.but when i test ouput signal with oscilloscope probe (10mohm)there is only a direct current at pin iout.i connect iout pin with a 50ohm res to gnd.i can not understand what happend?so i need your help thanks very much