ADRF6750 Analog Devices, Inc., ADRF6750 Datasheet - Page 32

• Manufacturer Part Number: ADRF6750
• Description: 950 Mhz To 1575 Mhz Quadrature Modulator With Integrated Fractional-n Pll And Vco
• Manufacturer: Analog Devices, Inc.

ADRF6750
EVALUATION BOARD
GENERAL DESCRIPTION
This board is designed to allow the user to evaluate the
performance of the ADRF6750. It contains the following:
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The evaluation board comes with associated software to allow
easy programming of the ADRF6750.
HARDWARE DESCRIPTION
For more information, refer to the circuit diagram in Figure 71.
Power Supplies
An external 5 V supply (DUT +5 V) drives both an on-chip
3.3 V regulator and the quadrature modulator.
The regulator feeds the VREG1 through VREG6 pins on the
chip with 3.3 V. These pins power the PLL circuitry.
The external reference clock generator can be driven by a 3 V
supply or by a 5 V supply. These supplies can be connected via
an SMA connector, VCO +V.
I/Q modulator with integrated fractional-N PLL and VCO
SPI and I
DC biasing and filter circuitry for the baseband inputs
Low-pass loop filter circuitry
10 MHz reference clock
Circuitry to support differential signaling to the TESTLO
inputs, including dc biasing circuitry
Circuitry to monitor the LOMON outputs
SMA connectors for power supplies and the RF output
2
C interface connectors
FEMALE
6
7
8
9
D-TYPE
9-WAY
1
2
3
4
5
Figure 70. SPI PC Cable Diagram
Rev. 0 | Page 32 of 40
DATA
CLK
GND
LE
PRINTER PORT
10
11
12
13
1
2
3
4
5
6
7
8
9
25-WAY
D-TYPE
TO PC
Recommended Decoupling for Supplies
The external 5 V supply is decoupled initially by a 10 μF capacitor
and then further by a parallel combination of 100 nF and 10 pF
capacitors that are placed as close to the DUT as possible for good
local decoupling. The regulator output should be decoupled by a
parallel combination of 10 pF and 220 μF capacitors. The 220 μF
capacitor decouples broadband noise, which leads to better phase
noise and is recommended for best performance. Case Size C
220 μF capacitors are used to minimize area. A parallel combi-
nation of 100 nF and 10 pF capacitors should be placed on each
VREGx pin. Again, these capacitors are placed as close to the pins
as possible. The impedance of all these capacitors should be low
and constant across a broad frequency range. Surface-mount
multilayered ceramic chip (MLCC) Class II capacitors provide
very low ESL and ESR, which assist in decoupling supply noise
effectively. They also provide good temperature stability and good
aging characteristics. Capacitance also changes vs. applied bias
voltage. Larger case sizes have less capacitance change vs. applied
bias voltage and also lower ESR but higher ESL. The 0603 size
capacitors provide a good compromise. X5R and X7R capacitors
are examples of these types of capacitors and are recommended
for decoupling.
SPI and I
The SPI interface connector is a 9-way, D-type connector that can
be connected to the printer port of a PC. Figure 70 shows the
PC cable diagram that must be used with the provided software.
There is also an option to use the I
receptacle connector. This is a standard I
resistors are required on the signal lines. The CS pin can be used
to set the slave address of the ADRF6750. CS high sets the slave
address to 0x60, and CS low sets the slave address to 0x40.
MALE
14
15
16
17
19
20
21
22
23
24
25
18
2
C Interface
PC
2
C interface by using the I
2
C connector. Pull-up
2
C