ADF4111BCP datasheet(19/28 Pages) AD

19 / 28 page

AD8348

Rev. A | Page 19 of 28

VCMO. This forms a high-pass response for the baseband

signal path with a lower 3 dB frequency of

COFS

PASS

2650

Alternatively, the user can externally adjust the dc offset by driving

IOFS (QOFS) with a digital-to-analog converter or other voltage

source. In this case, the baseband circuit operates all the way down

to dc (fPASS = 0 Hz). The integrator output current is only 50 μA

and can be easily overridden with an external voltage source.

The nominal voltage level applied to IOFS (QOFS) to produce

a 0 V differential offset at the baseband outputs is 900 mV.

The IOFS (QOFS) pin must be connected to either a bypass

capacitor (>0.1 μF) or an external voltage source to prevent the

feedback loop from oscillating.

The feedback loop will be broken at dc if an ac-coupled baseband

filter is placed between the mixer outputs and the baseband

amplifier inputs. If an ac-coupled filter is implemented, the user

must handle the offset compensation via some external means.

ADF4111BCP 数据表(PDF) 19 Page - Analog Devices