UG-521 Datasheet, PDF (3/8 Pages) Analog Devices – Evaluating the CN-0285 Wideband Tx Modulator Solution

Evaluation Board User Guide
EVALUATION BOARD HARDWARE
POWER SUPPLIES
The user must apply 5.5 V to the VSUPPLY power connectors
(4 mm banana connectors). An LED, D6, indicates when USB
power is available, and another LED, D5, indicates when the
main board is powered. Switch SW-EXT is used to switch in the
5.5 V supply.
IQ INPUTS
The ADL5375 has four differential IQ inputs. These are accessi-
ble from the SMA connectors and should be connected to an
appropriate analog baseband IQ source such as the Rhode &
Schwarz AMIQ. Set the dc bias voltage for the IQ inputs at 0.5 V.
RF/LO OUTPUTS
The ADL5375 RF output is ac-coupled out to the RFOUT SMA.
There are also two LO output SMA connectors that can be used
to view the filtered ADF4351 RF outputs on a spectrum analyzer.
When connecting to an analyzer, terminate the unused LO
output with a 50 Ω termination. When measuring EVM or
adjacent channel leakage current (ACLR), disconnect these LO
outputs by removing Capacitors C72 and C73 to prevent
loading the circuit.
LOOP FILTER AND CHARGE PUMP CURRENT
The loop filter schematic is included in the evaluation board
and can be found at www.analog.com/CN0285-DesignSupport.
UG-521
The default loop filter is set to 70 kHz. Using a charge pump
setting of 2.5 mA is recommended.
Figure 2. Loop Filter Layout
REFERENCE SOURCE
The 25 MHz TCXO from Rakon provides the necessary
reference signal. An external REFIN can be used if desired.
In this case, disable the on-board TCXO by removing R59.
R9 can be populated with 50 Ω to match the impedance of the
evaluation board to the external reference source.
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