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RFMD2080

DS140110

7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical

support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.

The differential I and Q input impedance is set by 10K

 pull down resistors on each pin, so presenting 20K differential

impedance. The baseband input signals will be typically 1Vp-p differential. A common mode DC voltage between 0.5V and 1.5V

is required for optimal performance. If required the phase and amplitude of either of the I or Q signal can be adjusted to

reduce the level of the unwanted sideband signal at the modulator output.

The baseband path consists of an active low pass filter with variable capacitors. The variable capacitors provide 64 "rctune"

settings that allow the input 3dB bandwidth to be tuned from 1.5MHz to 10MHz. This is followed by a variable gain attenuator

that delivers 0dB to -20dB gain in 2dB steps. Additionally, the mixers have gain control, ranging from 0dB to -18dB in 6dB

steps giving a maximum range of 38dB. The variable gain attenuator and mixer input have DACs attached to allow DC offsets

within the baseband path to be corrected, thus reducing LO breakthrough. An isolation switch sits between the variable gain

attenuator and the mixer input to allow their offsets to be compensated separately. This may be required since the offset within

the variable gain attenuator will vary with gain and thus its DC compensation may also have to vary for optimum LO cancella-

tion.

Serial Interface

All on-chip registers in the RFMD2080 are programmed using a proprietary 3-wire serial bus which supports both write and

read operations. Synthesizer programming, device configuration and control are achieved through a mixture of hardware and

software controls. Hardware pins can be used to control ENBL, MODE and RESETX or the device can be programmed entirely

via the serial bus.

The serial data interface can be configured for 4-wire operation, by setting the '4WIRE' bit in the SDI_CTRL register high. Then

pin 26 is used as the data out pin, and pin 32 is the serial data in pin.

bb_atten

DAC

DAC

dcdac_ai

dcdac_i

I_p

I_n

cal_blank

rc_tune

bb_atten

DAC

DAC

dcdac_aq

dcdac_q

Q_p

Q_n

cal_blank

I

Q

rc_tune

rc_tune

rc_tune

10K



10K



10K



10K

