RFFC5071A/2A

WIDEBAND SYNTHESIZER/VCO WITH

INTEGRATED 6 GHz MIXER

Data Sheet Rev. D, August 22, 2019 | Subject to change without notice

9 of 27

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The RFFC5071A mixer layout and pin placement has been optimized for high mixer-to-mixer isolation of greater than 60 dB. The mixers

can be set up to operate in half duplex mode (1 mixer active) or full duplex mode (both mixers active). This selection is done via control

of MODE and by setting the FULLD bit. When in full duplex mode, either PLL register bank can be used, the LO signal is routed to

both mixers.

Mode

FULLD

Active PLL Register Bank

Active Mixer

Low

0

1

1

High

0

2

2

Low

1

1

1 and 2

High

1

2

1 and 2

Serial Interface

All on-chip registers in the RFFC5071A and RFFC5072A 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. Certain functions and operations require the use of hardware controls via the ENBL, MODE, and RESETB pins in

addition to programming via the serial bus. Alternatively, there is the option to control the chip completely 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.

Hardware Control

Three hardware control pins are provided: ENBL, MODE, and RESETB.

The ENBL pin has two functions: to enable the analog circuits in the chip and to trigger the VCO auto-selection and coarse tuning

mechanisms. The VCO auto-selection and coarse tuning is initiated when the ENBL pin is taken high. Every time the frequency of the

synthesizer is reprogrammed, ENBL has to be asserted high to initiate these mechanisms and then to initiate the PLL locking. Alternatively

following the programming of a new frequency, the PLL re-lock self-clearing bit could be used.

The RESETB pin is a hardware reset control that will reset all digital circuits to their startup state when asserted low. The device includes

a power-on-reset function, so this pin should not normally be required, in which case it should be connected to the positive supply.

The MODE pin controls which mixer(s) and PLL programming register bank is active.

Serial Data Interface Control

The normal mode of operation uses the 3-wire serial data interface to program the device registers, and three extra hardware control

lines: MODE, ENBL and RESETB.

When the device is under software control, achieved by setting the SIPIN bit in the SDI_CTRL register high, then the hardware can be

controlled via the SDI_CTRL register. When this is the case, the three hardware control lines are not required. If the device is under

software control, pins 1 and 9 can be configured as general purpose outputs (GPO).