Each output buffer (A and B) have programmable
gain with register OUTA_POW and OUTB_POW. The RF output buffer configuration is
open-collector and requires an external pullup from RFout pin to VCC.
There are two pullup options that can be used with either resistor or inductor.
Refer to the Section 8 section for design considerations.
- Resistor pullup: placing a 50-Ω resistor pullup matches the output impedance to 50-Ω. However, maximum output power is limited. Output buffer current settings should be set to a value before output power is saturated (output power increases less for every step increase in output current value).
- Inductor pullup: placing an inductor pullup creates a resonance at the frequency of interest. This offers higher output power for the same current and higher maximum output power. However, the output impedance is higher and additional matching may be required..