Linear Technology DC1257B Guida rapida alla configurazione

dc1257bf

DEMO MANUAL DC1257B

DESCRIPTION

LTC6416

2 GHz Low Noise Differential

16-Bit ADC Buffer

Demonstration circuit 1257B features the LTC

6416, a

2GHz low noise differential 16-Bit ADC buffer driving the

LTC2208, a 16-bit 130Msps ADC. The DC1257B is sup-

plied with a bandpass filter centered at 140MHz between

the buffer and the ADC. The filter center frequency can be

changed to optimize performance at different analog input

frequencies. Both single-ended and differential configura-

tions are supported at the inputs. The DC1257B has been

Demonstration circuit 1257B is easy to set up. Refer to

Figure 1 for proper measurement equipment setup. Table 1

The DC1257B requires DC890 FastDAACs data acquisition

board with PScope System Software. The PScope System

Software is available from the Linear Technology website

at http://www.linear.com/software/.

Apply power to the DC1257B Demonstration Circuit. Apply

+3.6V across the pins marked OPT and GND, VS and GND.

The DC1257B demonstration circuit requires up to 100mA

from the OPT pin, and up to 700 mA from the VS pin.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation and PScope is a trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners.

developed from the DC996B-B, used to characterize the

LTC2208 family of ADCs.

Use the DC1257B with a DC890 FastDAACS and PScope™

software to collect time and frequency data.

Design files for this circuit board are available at

http://www.linear.com/demo

QUICK START PROCEDURE

HARDWARE SETUP

Table 1: DC1257B SMA Connector and Jumper Descriptions

J2 (AIN+) Single-Ended/Differential Input. By default, this is configured as a single-ended input. Use this connector to supply an input to

the DC1257B. When driven from a 50 signal source, no external termination necessary.

J3 (AIN–) Differential Input. Not connected by default. Capacitor C23 can be installed and C25 removed to drive the DC1257B differentially.

J4 (CLK) Single-Ended Input. This input is designed to be driven by an extremely low jitter 50 source. A sinusoidal input of up to 13dBm

is recommended.

JP1 (PGA) Programmable gain amplifier. Default to LOW Gain Mode. This sets the gain of the ADC amplifier to 1.0.

JP2 (RAND) ADC Digital Output Randomization. Default to OFF. This disables randomization.

JP3 (SHDN ADC) ADC Power Shutdown ADC. Default to EN. This results in normal operation.

JP4 (DITH) ADC Internal Dither Enable. Default to OFF. This disables internal dither.

describes the function of each SMA connector and default

settings for the jumpers on the board.

Supply power to the DC890B FastDAACS Board with an

external 6V ±0.5V 1A supply on turrets on G7(+) and G1(–)

or the adjacent 2.1mm power jack. Unless the DC890B

detects external power it will not activate the LVDS mode of

the Xilinx Spartan-III FPGA. The FPGA actively terminates

the LVDS repeaters at the outputs of the LTC2208.

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dc1257bf

DEMO MANUAL DC1257B

HARDWARE SETUP

Apply Encode Clock to the DC1257B on the SMA connector

marked “(J4) CLK". This transformer coupled input is

terminated with a 100 at the secondary and a 100 at

the ADC clock inputs. For best noise performance the clock

input must be driven with a very low jitter source. The

amplitude of the sinusoidal generator should be as large

as possible, up to 13dBm. Bandpass filters on the clock

and the analog input will improve the noise performance

by reducing the wideband noise power of the signals. Data

sheet FFT plots were taken with 10 pole LC filters made

by TTE (Los Angeles, CA) to suppress signal generator

harmonics, non-harmonically relatedspurs and broadband

noise. Low phase noise (jitter) Agilent 8644B generators

are used with TTE band pass filters for the CLK input and

Analog input.

Apply the Analog Input to the DC1257B on the SMA

connector marked "(J2) AIN+". This input is capacitively

coupled to a 1:4 Balun transformer TCM4-19+.

Start and Configure the PScope data collection software

for the FastDAACS DC890 by selecting AutoConfigure.

If the board is not detected, up-date PScope for latest

software and device list, and then select LTC2208 from the

Configure→Device menu.You can also manuallyconfigure

PScope for the LTC2208 by setting the parameters listed

in Table 2.

Table 2: PScope User Configuration for LTC2208

USER CONFIGURE

Bits 16

Channels 1

Alignment 16

FPGA Ld LVDS

Bipolar [x]

Positive Egde Clk [x]

Collect Data by clicking on the “Collect” button. Time and

frequency plots will be displayed in the PScope window.

Consult the DC890 Quick Start Guide for additional

information.

Buffer ADC Interface

The LTC6416 has been specifically designed to interface

directly with high speed A/D converters. It is possible

to drive the ADC directly from the LTC6416. In practice,

however, better SFDR may be obtained by adding a few

external components at the output of the LTC6416.

Figure 2 shows the LTC6416 being driven by a 1:4 trans-

former which provides 6 dB of voltage gain while also

performing single-ended to differential conversion. The

differential outputs of the LTC6416 are lowpass filtered

to drive the differential inputs of the LTC2208 ADC. In

many applications, an anti-alias filter like this is desir-

able to limit the wideband noise of the amplifier. This is

especially true in high performance 16-bit designs. The

minimum recommended network between the LTC6416

and the ADC is simply two 5 series resistors, which are

used to help eliminate resonances associated with the

stray capacitances of PCB traces and the stray inductance

of the internal bond wires at the ADC input, and the driver

output pins. Table 3 suggests filter components for dif-

ferent input frequencies.

Table 3. Suggested Components for the Filter

INPUT FREQUENCY LTC6416 OUTPUT

RESISTORS

R13 = R15

FILTERING CAPACITORS

C20/C22/C24

30MHz 50 5.6pF/6.8pF/5.6pF

70MHz 25 5.6pF/6.8pF/5.6pF

140MHz 25 1.5pF/1pF/1.5pF

250MHz 5 -/-/-

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dc1257bf

DEMO MANUAL DC1257B

HARDWARE SETUP

Figure 1. Demo Board DC1257B Layout

Figure 2. DC1257B Simplified Schematic with Recommended Output Termination for Driving an LTC2208 16-Bit ADC at 140MHz

V+

VCM

OUT–

6416 F05

OUT+

3.6V

2.2µF

IN+

CLHI

CLLO

IN–

LTC6416 1pF

1.5pF

3.3V

CLOCK

(130MHz)

DATA

VCM

LTC2208

AIN+

AIN–

25

GND

R36

100

R15

100

0.1µF

C39

0.01µF

50

680pF

TCM4-19+

–

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dc1257bf

DEMO MANUAL DC1257B

PARTS LIST

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

1 12 C8-C12, C19, C25, C26, C28-C31 CAP., X7R, 0.1µF, 25V, 20% 0603 AVX, 06033C104MAT2A

2 4 C13, C14, C18, C27 CAP., X5R, 0.1µF, 16V, 10% 0402 AVX, 0402YD104KAT2A

3 1 C16 CAP., X5R, 2.2µF, 6.3V, 10% 0603 AVX, 06036D225KAT2A

4 1 C17 CAP., C0G, 220pF, 16V, 10% 0402 AVX, 0402YA221KAT2A

5 2 C20, C24 CAP., C0G, 1.5pF, 50V, ±.25pf 0402 AVX, 04025A1R5CAT2A

6 1 C22 CAP., C0G, 1.0pF, 50V, ±.25pf 0402 AVX, 04025A1R0CAT2A

7 0 C21, C23 (OPT) CAP., 0603 (OPT)

8 1 C32 CAP., X5R, 10µF, 25V, 20% 1206 Taiyo Yuden, TMK316BJ106ML

9 1 C33 CAP., X5R, 10µF, 6.3V, 20% 0805 Taiyo Yuden, JMK212BJ106MG

10 5 E1, E2, E3, E5, E7 TESTPOINT, TURRET, .061" pbf MILL-MAX, 2308-2-00-80-00-00-07-0

11 2 E4, E6 TESTPOINT, TURRET, .094" pbf MILL-MAX, 2501-2-00-80-00-00-07-0

12 4 JP1, JP2, JP3, JP4 HEADER 3-PIN 0.079 SINGLE ROW SAMTEC, TMM103-02-L-S

13 4 JP1, JP2, JP3, JP4 SHUNT, .079" CENTER SAMTEC, 2SN-BK-G

14 3 J2, J3, J4 CON., SMA 50 EDGE-LAUNCH E.F. JOHNSON, 142-0701-851

15 0 L1 INDUCTOR, Ferrite Bead (OPT)

16 2 L2, L3 INDUCTOR, Ferrite Bead Murata, BLM18PG221SN1D

17 2 R3, R2 RES., CHIP, 10, 1/16W, 5% 0402 VISHAY, CRCW040210R0JNED

18 1 R4 RES., CHIP, 1k, 1/16W, 5% 0402 VISHAY, CRCW04021K00FKED

19 0 R5, R6, R8, R10-R12, R17, R18 (OPT) RES., CHIP, 0402 (OPT)

20 1 R7 RES., CHIP, 100, 1/16W, 5% 0402 VISHAY, CRCW0402100RJNED

21 2 R13, R15 RES., CHIP, 24.9, 1/16W, 1% 0402 VISHAY, CRCW040224R9FKED

22 2 R14A, R14B RES., CHIP, 100, 1/16W, 1% 0402 VISHAY, CRCW0402100FKED

23 1 R9, (Bal to#1450A) RES., CHIP, 10.0, 1/16W, 1% 0402 VISHAY, CRCW040210R0FKED

24 1 R16 RES., CHIP, 5.1k, 1/16W, 5% 0603 VISHAY, CRCW06035K10JNEA

25 2 R26, R19 RES., CHIP, 51.1, 1/16W, 1% 0402 VISHAY, CRCW040251R1FKED

26 1 R21 RES., CHIP, 100, 0.05W, 5% 0201 VISHAY, CRCW0201J100JNTD

27 3 R24, R25, R28 RES., CHIP, 4.99k, 1/16W, 1% 0603 VISHAY, CRCW06034K99FKEA

28 1 R27 RES., CHIP, 2k, 1/16W, 5% 0603 VISHAY, CRCW06032K00JNEA

29 0 R29 (OPT) RES., CHIP, 0603 (OPT)

30 1 T1 TRANSFORMER, TCM4-19+ MiNi-Circuits, TCM4-19+

31 1 T2 TRANSFORMER, ETC1-1-13, SM-22 M/A-COM, MABA-001759-000000

32 1 U1 lot#T28918.2 DC=0837 I.C. LTC2208CUP 9 × 9 QFN LINEAR, LTC2208CUP#PBF

33 1 U2 lot#J20129.1 DC=0808 I.C. LTC6416CDDB DFN 10-PIN (3 × 2) LINEAR, LTC6416CDDB#PBF

34 1 U3 I.C., 24LC025, TSSOP-8 MICROCHIP, 24LC025 I /ST

35 1 U4 see file for #'s IC., LT1963AEST-3.3 SOT-223 LINEAR, LT1963AEST-3.3#PBF

36 4 (STAND-OFF) STAND-OFF, NYLON 0.25" KEYSTONE, 8831(SNAP ON)

37 1 FAB, PRINTED CIRCUIT BOARD DEMO CIRCUIT 1257B

38 1 STENCIL STENCIL 1257B

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dc1257bf

DEMO MANUAL DC1257B

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

SCHEMATIC DIAGRAM

Figure 3. Demo Board DC1257B Schematic (Test Circuit B)

LTC2208CUP

SENSE

GND

VCM

GND

VDD

GND

AIN+

AIN−

GND

ENC+

ENC−

GND

VDD

VCM

DA6

DA5

DA4

DA3

DA2

DA1

DA0

CLKCOUTA

CLKCOUTB

OFB

DB15

DB14

DB13

DB12

DB11

DB10

PGA

RAND

MODE

LVDS

OFA

DA15

DA14

DA13

DA12

DA11

DA10

DA9

DA8

DA7

OGND

OVDD

VDD

GND

SHDN

DITH

DB0

DB1

DB2

DB3

DB4

DB5

DB6

DB7

DB8

DB9

OGND

OVDD

GND

C22

1pF

R13

24.9Ω

R15

24.9Ω

C24

1.5pF

C20

1.5pF

C16

2.2µF

C14

0.1µF

C17

680pF

R7, 100

OPT

OFF

VDD VDD

JP2

RAND

10

JP1

PGA

LOW

EXTREF

CLHI

CLLO

VDD

OVP

C12

0.1µF

C11

0.1µF

6416 F09

R28

4.99k

R25

4.99k

C31

0.1µF

R24

4.99k

R29

OPT

R27

24LC025

VCC

SCL

SDA

VSS

OFF

SHDN

JP3

SHDN ADC

JP4

DITH

VDD

C10

0.1µF

••

C30

0.1µF

R19

51.1Ω

R26

51.1Ω

C28

0.1µF

MABA-007159-000000

R21

100Ω

CLK

C29

0.1µF

GND

3.6V TO 20V

LT1963AEST-3.3

GND E5E4

OPT

IN OUT

C32

10µF

25V

C33

10µF

6.3V

L1(opt.)

BLM18PG221SN1D

VDD

VCC

OVP

LTC6416CDDB

VCC

C26

0.1µF

TCM4−19+

C25

0.1µF

C27

0.1µF

C13

0.1µF

C21

OPT

R14A

100Ω

R14B

100Ω

V+

GND

OUT+

OUT−

GND

VCM

CLHI

IN+

IN−

CLLO GND

C19

0.1µF

C23

OPT

R10

OPT

VCC

C18

0.1µF

R11

OPT

R12

OPT

VCC

R17

OPT

R18

OPT

VCM

••

100

R16

5.1k

EDGE-CON

(GOLD FINGER)

OVP

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dc1257bf

DEMO MANUAL DC1257B

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ●FAX: (408) 434-0507 ●www.linear.com

LT 0812 • PRINTED IN USA

DEMONSTRATION BOARD IMPORTANT NOTICE

Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:

This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT

OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete

in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety

measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union

directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.

If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date

of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU

OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS

FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR

ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.

The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims

arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all

appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or

agency certified (FCC, UL, CE, etc.).

No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,

customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.

LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.

Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and

observe good laboratory practice standards. Common sense is encouraged.

This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC applica-

tion engineer.

Mailing Address:

Linear Technology

1630 McCarthy Blvd.

Milpitas, CA 95035

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