Preliminary Technical Data
EVAL-AD5934EB
Rev. PrC | Page 5 of 32
Link No.
Function
LK11
The on-board voltage reference ADR423 (U4) can be supplied with an external supply voltage at Terminal Block J6-1.
Alternatively, the input voltage can be supplied to the reference by the 5 V available through the USB connector (J1). By
inserting LK11, LK5, LK4, and LK10, the AD5934 is completely powered from the USB supply; however, it is recommended to
power the three supply pins of the part from an external precision voltage source for best results.
LK12
This link is used to connect the high performance 16 MHz crystal oscillator (Y2) to Pin 8 (MCLK) of the AD5934.
•
When Link 12 (LK12) is inserted and Link 3 (LK3) is removed, the on-board crystal oscillator is connected to the MCLK pin.
•
When Link 12 (LK12) is removed, Link 3 (LK3) should be inserted and an external clock should be applied to the CLK1 SMB
connector.
SMB JUMPER FUNCTIONS
Table 3. SMB Jumper Function Descriptions
SMB Function
CLK 1
The user must apply an external clock signal to Pin 8 (MCLK) of the AD5934 for the internal DDS core and ADC.
When Link 3 is inserted and Link 12 is removed, the external clock signal applied at the CLK1 SMB connector is connected to
Pin 8 (MCLK). Alternatively, if Link 3 is removed and Link 12 is inserted, the on-board high performance 16 MHz surface-mount
crystal can be used to clock the system.
CLK 2
This link is for test purposes only.
VOUT
The user connects one end of the impedance being analyzed (Z
UNKNOWN
) to this connector and the other end across the VIN
SMB connector. The signal present at this connector can either be the excitation voltage output from Pin 6 of the AD5934 or
an amplified version, depending on the status of LK1, LK2, and LK6, assuming the presence of a user-supplied external op amp at
U1 (see Figure 1).
VIN
This connector takes the response signal current from across the impedance being analyzed (Z
UNKNOWN
), which is connected
between the VIN and VOUT SMB connectors, and provides a path back to the input pin (VIN, Pin 5). Link 7 must be inserted for
the path to be complete. The external feedback resistor (RFB) has one point connected to this signal path, as shown in the
board schematic (see the Evaluation Board Schematic section) and Figure 2.
LINK SETUP CONDITIONS
Table 4. Default Link Positions (Refer to Figure 2 )
Link Position Function
LK1,
LK2
Removed
External Amplifier U1 (optional) connected to VOUT is disconnected. AD5934 VOUT is directly connected to the SMB
connector VOUT.
LK3
Removed
Used in conjunction with Link 12 (LK12). Optional user-supplied clock signal at CLK1 is not connected to Pin 8 (MCLK).
LK4
Inserted
AVDD1 is supplied from the ADR423 reference output.
LK5
Inserted
AVDD2 is supplied from the ADR423 reference output.
LK6
Inserted
Connects the output pin of the AD5934, VOUT, to the VOUT SMB connector.
LK7
Inserted
Connects the input pin of the AD5934, VIN, to the VIN SMB connector.
LK8,
LK9
Inserted
Connects a 15 pF capacitor across the input and output pins of the AD5934. These links are for board manufacturing
test purposes only and should be removed when completing a sweep with impedance Z
UNKNOWN
connected between
the SMB connectors, VOUT and VIN.
LK10
Inserted
DVDD is supplied from the ADR423 reference output.
LK11 Inserted
Connects the 5.0 V supplied from the USB hub of the user PC to the supply input (VDD, Pin 2 of U4) of the on-board
ADR423 reference.
LK12
Inserted
Connects the output of the on-board 16 MHz oscillator to Pin 8 (MCLK) of the AD5934.