Differences between ADF41020 and ADF4108

Question What is the differences between ADF41020 and ADF4108? Answer The ADF41020 covers 4-18GHz compared to 1-8GHz for the ADF4108. The ADF41020 is software compatible with the ADF4106/07/08.

ADF41020 volatile registers

Question In the datasheet of ADF41020 it says under “applications” mobile systems, automotive systems and handheld radios. Surely the PLL chips inside have to be non-volatile. But ADF41020 seems to have volatile registers only. Can you advise a solution? Answer The registers are volatile and will lose their content when power is removed. On the ADF41020 and our other PLL’s we have power-down modes which power-down the part ( for this software (register write) or hardware (CE pin) So if you require the register to maintain content you can bring CE low and the part powers down. When CE is brought back high the part will lock without any register writes required.

Question What type of external caps is required for charge pump caps and decoupling caps. Answer Small ceramic caps are fine (0603 or 0402 size). COG capacitors are preferred.

Layout Considerations

Question Are there any layout considerations when designing in this device. Answer The decoupling caps should be placed as close as possible to the device. RF transmission lines are required to carry the high frequency signals.

Fixed divide-by-4 prescalar

Question Are there any “gotchas” when using the part? Answer With the fixed divide-by-4 prescalar the RF frequency step size is 4x the PFD frequency.

Suitable Reference Sources

Question What reference sources are suitable? Answer This is often determined by the application. But sinusoidal, low noise references such as TCXO’s, or better OCXO’s are recommended. Clock distribution signals are also suitable.