RFFC2071 Datasheet, PDF (9/23 Pages) RF Micro Devices – 2.7GHz RF SYNTHESIZER/VCO WITH INTEGRATED RF MIXER

RFFC2071/2072
Multi-Slice Mode
ENX
SDATA
SCLK
Slice2
(0)
A1 A2
Slice2
(1)
A1 A2
Vdd
Slice2
(2)
A1 A2
Vdd
Slice2
(3)
A1 A2
Vdd
Vdd
The Multi-Slice mode of operation allows up to four chips to be controlled from a common serial bus. The device address pins
(15 and 16) ADD1 and ADD2 are used to set the address of each part.
On power up, and after a reset, the devices ignore the address pins ADD1 and ADD2 and any data presented to the serial bus
will be programmed into all the devices. However, once the ADDR bit in the SDI_CTRL register is set, each device then adopts
an address according to the state of the address pins on the device.
General Purpose Outputs
The general purpose outputs (GPOs) can be controlled via the GPO register and will depend on the state of MODE since they
can be set in different states corresponding to either mixer path 1 or 2. For example, the GPOs can be used to drive LEDs or to
control external circuitry such as switches or low power LNAs.
Each GPO pin can supply approximately 20mA load current. The output voltage of the GPO high state will drop with increased
current drive by approximately 25mV/mA. Similarly the output voltage of the GPO low state will rise with increased current,
again by approximately 25mV/mA.
External Modulation
The RFFC2071 and RFFC2072 fractional-N synthesizer can be used to modulate the frequency of the VCO. There are two dedi-
cated registers, EXT_MOD and FMOD, which can be used to configure the device as a modulator. It is possible to modulate the
VCO in two ways:
1.Binary FSK
The MODSETUP bits in the EXT_MOD register are set to 11. GPO3 is then configured as an input and used to control the signal
frequency. The frequency deviation is set by the MODSTEP and MODULATION bits in the EXT_MOD and FMOD registers respec-
tively.
The modulation frequency is calculated according to the following formula:
F_MOD = 2^MODSTEP  F_PD  MODULATION  2¹⁶
Where MODULATION is a 2's complement number and F_PD is the phase detector frequency.
2.Continuous Modulation
The MODSETUP bits in the EXT_MOD register are set to 01. The frequency deviation is set by the MODSTEP and MODULATION
bits in the EXT_MOD and FMOD registers respectively. The VCO frequency is then changed by writing a new value into the MOD-
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