Evaluation Board User Guide

UG-521

Rev. 0 | Page 3 of 8

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.

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.