AD9214 datasheet(15/21 Pages) AD

15 / 21 page

REV. D

AD9214

–14–

Reference Circuit

The evaluation board is configured at assembly to use the

AD9214’s on-board reference. To supply an external reference,

the user must connect the REFSENSE pin to VCC by removing

the jumper block connecting E25 to E26, and placing it between

E19 and E24. In this configuration, an external 1.25 V reference

must be connected to jumper connection E23. Jumper connections

E19–E21, E24, and resistors R13–R14 are omitted at assembly,

and not used in the evaluation of the AD9214.

Gain/Data Format

The evaluation board is assembled with the DFS/GAIN pin

connected to ground; this configures the AD9214 for a 1 V p-p

analog input range, and offset binary data format. The user may

remove this jumper and replace it to make one of the connections

described in the table below to configure the AD9214 for different

gain and output data format options.

Table III. Data Format and Gain Configuration for

Evaluation Board

DFS/GAIN

Jumper

DFS/GAIN

Differential Output Data

Placement

Connection

AIN Range

Format

E18 to E12

AGND

1 V p-p

Offset Binary

E16 to E11

AVDD

1 V p-p

Two’s Complement

E15 to E14

REF

2 V p-p

Two’s Complement

E17 to E13

Floating

2 V p-p

Offset Binary

Power-Down

The evaluation board is configured at assembly so that the

PWRDN input floats low for normal operating condition. The

user may add a jumper between option holes E5 and E6 to

connect PWRDN to AVCC, configuring the AD9214 for power-

down mode.

Encode Signal and Distribution

The encode input signal should drive SMB connector J5, which

has an on-board 50

Ω termination. A standard CMOS compatible

pulse source is recommended. Alternatively, the user can adjust

the dc level of an ac-coupled clock source by adding resistor

R11, normally omitted. J5 drives the AD9214 ENCODE input

and one gate of U12, which buffers and distributes the clock

signal to the on-board latch (U3), the reconstruction DAC

(U11), and the output data connector (U2). The board comes

assembled with timing options optimized for the DAC and latch;

the user may invert the DR signal at Pin 37 of edge connector

U2 by removing the jumper block between E34 and E35, and

reinstalling it between E35 and E36.

Analog Input

The analog input signal is connected to the evaluation board by

SMB connector J1. As configured at assembly, the signal is ac

coupled by capacitor C10 to transformer T1. This 1:1 transformer

provides a 50

Ω termination for connector J1 via 25 Ω resistors

R1 and R4. T1 also converts the signal at J1 into a differential

signal for the analog inputs of the AD9214. Resistor R3, normally

omitted, can be used to terminate J1 if the transformer is removed.

The user can reconfigure the board to drive the AD9214 single-

endedly by removing the jumper block between E1 and E3, and

replacing it between E3 and E2. In this configuration, capacitor

C2 stabilizes the self-bias of

AIN, and resistor R2 provides a

matched impedance for a 50

Ω source at J1.

Transformer T1 can be bypassed by moving the jumper normally

between E40 and E38 to connect E40 to E37, and moving the

jumper normally between E39 and E10 to connect E7 to E10.

In this configuration, the analog input of the AD9214 is driven

single ended, directly from J1; and R3 (normally omitted) should

be installed to terminate any cable connected to J1.

Using the AD8138

An optional driver circuit for the analog input, based on the

AD8138 differential amplifier, is included in the layout of the

AD9214 evaluation board. This portion of the evaluation circuit

is not populated when the board is manufactured, but can be

easily be added by the user. Resistors R5, R16, R18, and R25

are the feedback network that sets the gain of the AD8138.

Resistors R23 and R24 set the common-mode voltage at the

output of the op amp. Resistors R27 and R28, and capacitor

C15, form a low-pass filter at the output of the AD8138, limiting

its noise contribution into the AD9214.

Once the drive circuit is populated, the user should remove the

jumper block normally between E40 and E38, and place it between

E40 and E41. This will ac-couple the analog input signal from

SMB connector J1 to the AD8138 drive circuit. The user will also

need to remove the jumper blocks that normally connect E39 to

E10 and E1 to E3 to remove transformer T1 from the circuit.

DAC Reconstruction Circuit

The data available at output connector U2 is also reconstructed by

DAC U11, the AD9752. This 12-bit, high-speed digital-to-analog

converter is included as a tool in setting up and debugging the

evaluation board. It should not be used to measure the per-

formance of the AD9214, as its performance will not accurately

reflect the performance of the ADC. The DAC’s output, available

at J2, will drive 50

Ω. The user can add a jumper block between

E8 and E9 to activate the SLEEP function of the DAC.

AD9214 Datasheet(PDF) 15 Page - Analog Devices

AD9214 Datasheet(HTML) 15 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Datasheet Download

Link URL