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ADL5240 SPI/serial control issues

Question asked by Yann-fr on Mar 16, 2018
Latest reply on Mar 19, 2018 by Yann-fr

Hi everybody,

I'm having issues when trying to set an attenuation level on the ADL5240 DSA.

I'm in the serial mode and so using pins 31/30/29 as CLK/DATA/Latch. The SEL pin is tied to GND. D3/D4/D5 pins are also connected to GND. Pin 25 (D6) is connected to VDD (+5VDC).

Attached is a scope plot (1dB request timing diagram: yellow=CLK, green=DATA, purple=LE) of my SPI sequence.

It looks OK when compared to the ADL5240 data sheet fig35 but I don't see any effect of my RF level.

May be my problem is on D6 as I have a permanent logic high level on this pin ?

Any suggestion is welcome.

Thanks !