Question
Which is the ramp triggering pin on the ADF4158? I couldn’t find any. The nearest guess for me would be the LE pin (load enable on the serialinterface), assuming that the last command written was to set the “Ramp ON” bit in R0. Is my assumption correct? Would it in that case be necessaryto shift-in again the 32 bits to R0 in order to repeat the same ramp? Or is it sufficient to pulse the LE pin? (I understand that the LE pin copiesthe content from the shift register to the actual data register, which makes the command effective).
Answer
The ADF4158 does not have a dedicated hardware trigger pin but your assumption on how LE works is correct. You cannot just pulse the pin – the partrequires 32 bits before the low to high LE transition. On the next reference edge the sweep will start assuming R0[31]=1.The ADF4159 can use the TXdata pin as a dedicated hardware trigger when R7[20]=1. A logic high on the TXdata pin enables the sweep.