TRF371125: Fast gain control problem

Part Number: TRF371125

I use the RF371125 in my project.

Baseband gain is set to 15dB (register 1 bits 16-12).

Fast gain control bit (EN_FASTGAIN, register 1 bit 27) is set to "1" .

When switching the logic inputs Gain_B0, Gain_B1 and Gain_B2 (Fast gain input) from "000" to "111" I get a 7dB amplitude jump at the output regardless the state of Fast-gain control multiplier bit (register 1 bit 28).

The input test signal is at a low amplitude so it has at least 20 dB dynamic range to higher or lower signal so there enough margin from gain compression or noise floor.

Why can't I get a 14 dB gain jump when Fast-gain control multiplier bit (Register1 bit28) is "1" and I switch the fast gain inputs between "000" and "111"? What am I doing wrong?

Victor Koren

2 Replies