AD6644

–14–

REV. 0

AD6644ST/PCB Bill of Material

Item

Quantity

Reference

Description

1

2

C1, C2

Tantalum Chip Capacitor 10

µF

2

19

C3, C7, C8, C9, C10, C11, C16, C30, C31,

Ceramic Chip Capacitor 0508, 0.1

µF

C32, C4, C22, C23, C24, C25, C26, C27,

C28, C29

3

8

C12, C13, C14, C17, C18, C19, C20, C21

Ceramic Chip Capacitor 0508, 0.01

µF

4

1

CR1

HSMS2812 Surface Mount Diode

5

1

E3, E4, E5

3-Pin Header

6

4

F1, F2, F3, F4

Ferrite (Optional)

7

2

J1, J6

PCTB2

8

1

J2

50-Pin Double Row Header

9

1

J3

SMA Connector

10

2

J4, J5

BNC Connector

11

1

R1

Surface-Mount Resistor 1206, 100

Ω

12

1

R2

Surface-Mount Resistor 1206, 60.4

Ω

13

4

R3, R4, R5, R8

Surface-Mount Resistor 0805, 499

Ω (Optional,

DC-Coupling Only)

14

2

R6, R7

Surface-Mount Resistor 0805, 25

Ω

15

1

R9

Surface-Mount Resistor 0805, 348

Ω

16

1

R10

Surface-Mount Resistor 0805, 615

Ω

17

1

R35

Surface-Mount Resistor 0805, 49.9

Ω

18

30

R36, R37, R38, R39, R40, R41, R42, R43,

Surface-Mount Resistor 0402, 100

Ω

R44, R45, R46, R47, R48, R49, R50, R51,

R52, R53, R54, R55, R56, R57, R58, R59,

R60, R61, R62, R63, R64, R65

19

2

T2, T3

Surface-Mount Transformer Mini-Circuits T4–1, 1:4 Ratio

20

1

U1

AD6644AST 14-Bit 65 MSPS A/D Converter

21

2

U2, U7

74LCX574 Octal Latch

22

1

U3

AD8138 Single-to-Differential Amplifier (Optional – DC

Coupling Only)

23

2

U4, U6

NC7SZ32 Two Input OR Gate

24

1

U5

CTS Reeves Full-Size MX045 Crystal Clock Oscillator

EVALUATION BOARD

The evaluation board for the AD6644 is straightforward,

containing all required circuitry for evaluating the device. The

only external connections required are power supplies, clock,

and the analog inputs. The evaluation board includes the option

for an onboard clock oscillator for ENCODE.

Power to the analog supply pins of the AD6644 is connected via

the power terminal block (PCTB2). Power for the digital interface

is supplied via pin 1 of J6. The J2 connector mates directly with

SoftCell Receive Signal Processor (AD6620, AD6624) evaluation

boards, allowing complete evaluation of system performance.

The analog input is connected via a BNC connector AIN, which

is transformer-coupled to the AD6644 inputs. The transformer

has a turns ratio of 1:4 to reduce the amount of input power

required to drive the AD6644.

The Encode signal may be generated using an onboard crystal

oscillator, U5. The on-board oscillator may be replaced by an

external encode source via the SMA connector labeled OPT_CLK

or BNC connector labeled ENCODE. If an external source is

used, it must be a high-quality and very low-phase noise source.

The AD6644 output data is latched using 74LCX574 (U7, U2)

latches. The clock for these latches is determined by selecting

jumper E3–E4 or E4–E5. E3 to E5 is a just a gate delayed ver-

sion of the clock, while connecting E4 to E5 utilizes the Data

Ready of the AD6644 to latch the output data. A clock is also

distributed with the output data (J2) that is labeled BUFLAT

(Pin 19 and 20, J2).