LTC2288CUP#PBF - ANALOG DEVICES

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 816

10/12/14 BIT 10 TO 65 MSPS DUAL ADC

LTC2286, LTC2287, LTC2288, LTC2290, LTC2291, LTC2292, LTC2293, LTC2294,

LTC2295, LTC2296, LTC2297, LTC2298 or LTC2299

DESCRIPTION

Demonstration circuit 816 supports a family of

10/12/14 BIT 10 TO 65 MSPS DUAL ADCs. Each

assembly features one of the following devices:

LTC2286 thru LTC2298 high speed, high dynamic

range ADCs.

Several versions of the 816A demo board support-

ing the LTC2286-2288 10 BIT, LTC2290-2293 12

BIT and LTC2295-2298 14 BIT series of A/D con-

verters are listed in Table 1. Depending on the re-

quired resolution, sample rate and input frequency,

the DC816 is supplied with the appropriate A/D and

with an optimized input circuit. The circuitry on

the analog inputs is optimized for analog input fre-

quencies below 70 MHz or from 70 MHz to 140MHz

for 12 and 14 bit versions. The 10 bit versions are

configured with a wider 1MHz to 200MHz front end

as the lower resolution 10 bit converters are not as

sensitive to noise. For higher input frequencies,

contact the factory for support.

Design files for this circuit board are available.

Call the LTC factory.

LTC is a trademark of Linear Technology Corpora-

tion

Table 1.

DC816A Variants

DC816 VARIANTS ADC PART NUMBER RESOLUTION* MAXIMUM SAMPLE RATE INPUT FREQUENCY

816A-B LTC2298 14-Bit 65Msps 1MHz - 70MHz

816A-C LTC2297 14-Bit 40Msps 1MHz -70MHz

816A-D LTC2296 14-Bit 25Msps 1MHz - 70MHz

816A-E LTC2295 14-bit 10Msps 1MHz - 70MHz

816A-G LTC2298 14-Bit 65Msps 70MHz -170MHz

816A-I LTC2293 12-Bit 65Msps 1MHz - 70MHz

816A-J LTC2292 12-Bit 40Msps 1MHz - 70MHz

816A-K LTC2291 12-Bit 25Msps 1MHz - 70MHz

816A-L LTC2290 12-Bit 10Msps 1MHz - 70MHz

816A-N LTC2293 12-Bit 65Msps 70MHz -170MHz

816A-P LTC2288 10-Bit 65Msps 1MHz - 70MHz

816A-Q LTC2287 10-Bit 40Msps 1MHz - 70MHz

816A-R LTC2286 10-Bit 25Msps 1MHz - 70MHz

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 816

10/12/14 BIT 10 TO 65 MSPS DUAL ADC

Table 2.

Performance Summary (TA = 25°C)

PARAMETER CONDITION VALUE

Supply Voltage Depending on sampling rate and the A/D converter provided,

this supply must provide up to 150mA.

Optimized for 3.0V

[2.7V 3.6V min/max]

Analog input range Depending on Sense Pin Voltage 1V

to 2V

Minimum Logic High 2.4V

Logic Input Voltages

Maximum Logic Low 0.8V

Minimum Logic High @ -1.6mA 2.3V (33•••Series terminations) Logic Output Voltage

(74VCX245 output buffer, V

= 2.5V) Maximum Logic Low @ 1.6mA 0.7V (33•••Series terminations)

Sampling Frequency (Convert Clock Frequency) See Table 1

Convert Clock Level 50 • Source Impedance, AC coupled or ground referenced

(Convert Clock input is capacitor coupled on board and ter-

minated with 50•.)

P-P 

2.5V

P-P

Sine Wave

or Square wave

Resolution See Table 1

Input frequency range See Table 1

SFDR See Applicable Data Sheet

SNR See Applicable Data Sheet

QUICK START PROCEDURE

Demonstration circuit 816 is easy to set up to evalu-

ate the performance of most members of the

LTC229X family of Dual A/D converters – LTC2286,

LTC2287, LTC2288, LTC2290, LTC2291, LTC2292,

LTC2293, LTC2295, LTC2296, LTC2297, or LTC2298.

The 80 Msps (LTC2299, LTC2294 and LTC2289) and

follow-on higher sample rate versions will not be

supported by the DC718, and have a different demo

board and higher speed data collection board. Refer

to Figure 1 for proper measurement equipment setup

and follow the procedure below:

SETUP

If a DC718 QuickDATS Data Acquisition and Test Sys-

tem was supplied with the DC816 demonstration cir-

cuit, follow the DC718 Quick Start Guide to install the

required software and for connecting the DC718 to the

DC816 and to a PC running Windows98, 2000 or XP.

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 816

10/12/14 BIT 10 TO 65 MSPS DUAL ADC

Figure 1. DC816 Setup

DC816 DEMONSTRATION CIRCUIT BOARD JUMPERS

The DC816 demonstration circuit board

should have the following jumper settings

as default: (as per figure 1)

JP1: Mode: Vdd. 2s complement, Clock duty stabi-

lizer off (see data sheet for function of Mode pin.)

JP2: Sense A: Vdd, (2V P-P input range)

JP3: Sense B: Vdd, (2V P-P input range)

APPLYING POWER AND SIGNALS TO THE DC816

DEMONSTRATION CIRCUIT BOARD:

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 816

10/12/14 BIT 10 TO 65 MSPS DUAL ADC

If a DC718 is used to acquire data from the DC816,

the DC718 must FIRST be connected to a powered

USB port or provided an external 6-9V BEFORE ap-

plying +3V across the pins marked “+3.0V” and

“PWR GND” on the DC816. The DC816 demonstra-

tion circuit requires up to 200 mA depending on the

sampling rate and the A/D converter supplied.

The DC718 data collection board is powered by the

USB cable and does not require an external power

supply unless it must be connected to the PC

through an un-powered hub in which case it must

be supplied an external 6-9V on turrets G7(+) and

G1(-) or the adjacent 2.1mm power jack.

ENCODE CLOCK

NOTE: As shipped, this is not a logic compatible

input. It is terminated with 50 Ohms. For higher

conversion rates, the encode clock can be a sinu-

soidal signal. For lower conversion rates (<25

Msps), this input should be driven with a square

wave signal source, as the dvdt at the output of the

clock buffer (U3) is less than 2x that at the SMA

connector, and is inadequate both in terms of phase

noise, as well as ensuring repeatable output timing

due to differences in threshold voltages between

the ADC, and buffer U6.

Apply an encode clock to the SMA connector on the

DC816 demonstration circuit board marked “J3

CLOCK INPUT”. This input is connected to ground

through a 50• resistor R14, and followed by a

blocking capacitor. For the best noise performance,

the CLOCK INPUT must be driven with a very low

jitter source. When using a sinusoidal generator,

the amplitude should be as large as possible, up to

P-P

or 13 dBm. Using band pass 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 are taken with

10 pole LC filters made by TTE (Los Angeles, CA) to

suppress signal generator harmonics,

non-harmonically related spurs and broad band

noise. Low phase noise Agilent 8644B generators

are used with TTE band pass filters for both the

Clock input and the Analog input.

[The Encode Clock can be driven with a 2.5V to

3.3V CMOS Logic Level square wave if R14 is re-

placed with an acceptable load for the drive capabil-

ity of the logic. Note that logic devices are gener-

ally not able to drive cable. A barrel is recom-

mended for logic drive. If a cable is used, the cable

carrying the clock signal must be terminated to

maintain the signal integrity of the Encode Clock

Source and the signal source must be able to drive

the 0 to 2.5V square wave signal into 50••load••

Apply the analog input signals of interest to the

SMA connectors on the DC816 demonstration cir-

cuit board marked “ANALOG INPUT (A and B)”.

These inputs are capacitive coupled to Balun trans-

formers ETC1-1-13, or directly coupled through

Flux coupled transformers ETC1-1T.

A doubled conversion clock output is available on

pin 3 of J2 and the data samples are available on

Pins 11-37 for 14 BITS or (15-37 for 12 BITS) of J2

which can be collected via a logic analyzer, cabled

to a development system through a SHORT 2 to 4

inch long 40 pin ribbon cable or collected by the

DC718 QuickEval-II Data Acquisition Board using

the

PScope System Software

provided or down

loaded from the Linear Technology website at

http://www.linear.com/software/. If a DC718 was

provided, follow the DC718 Quick Start Guide and

the instructions below.

To start the data collection software if

“

PScope.exe

”, is installed (by default) in

\Program Files\LTC\PScope\, double click the

PScope Icon or bring up the run window under the

start menu and browse to the PScope directory and

select PScope.

Configure PScope for the appropriate variant of the

DC816 demonstration circuit by selecting the cor-

rect A/D Converter as installed on the DC816. Un-

der the “Configure” menu, go to “Device.” Under

the “Device” pull down menu, select device,

LTC2286, through LTC2298. When evaluating 12

or 10 BIT parts, select the appropriate LTC229X

part in the Device List and PScope will automati-

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 816

10/12/14 BIT 10 TO 65 MSPS DUAL ADC

cally blank the last two or four LSBs when using a

DC816 supplied with a 14 BIT part.

If everything is hooked up properly, powered and a

suitable convert clock is present, clicking the “Col-

lect” button should result in time and frequency

plots displayed in the PScope window. The two

channel mode in Pscope provides a page for each

channel, and a page showing the frequency domain

plots of both channels. An additional window called

“X-channel” displays relative phase and amplitude

of the two channels. This can be used to gauge

cross-talk, or validate relative aperture. Additional

information and help for

PScope

is available in the

DC718 Quick Start Guide and in the online help

available within the

PScope

program itself.

ANALOG INPUT NETWORK

For optimal distortion and noise performance the

RC network on the analog inputs are optimized for

different analog input frequencies on the different

versions of the DC816. For input frequencies below

about 70 MHz, the circuit in Fig. 2 is recommended

(this is installed on DC816 versions A,B,C,D,E). For

input frequencies above 70 MHz and below

170 MHz, the circuit in Fig. 3 is recommended (this

is installed on versions F,G).

For input frequencies between 170 and 250MHz,

connect the transformer outputs directly to the ADC

inputs without the RC filter. For input frequencies

between 250 MHz and 500 MHz, the circuit in Fig. 4

is recommended. For input frequencies greater

than 250 MHz contact the factory for support.

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 816

10/12/14 BIT 10 TO 65 MSPS DUAL ADC

Figure 2. Analog Front End Circuit For 1MHz < A

< 70MHz (1 of 2)

Figure 3. Analog Front End Circuit For 70MHz < A

< 170MHz (1 of 2)

Figure 4. Analog Front End Circuit For 300MHz < A

< 500MHz

Note that relative aperture measurements require removal of these networks, or the results will simply show the relative phase

through the RC network. The measure of relative phase further requires a resistive power divider, and matched cables, or the

results will be misleading. Any relative phase measurements should be confirmed by reversing the signals to confirm that the

relative delay is not due to the external network.

If relative phase measurements produce results of greater that a fractional psec, please consult the factory for

assistance.

Channel to Crosstalk on this demo board better than -110 dB below 140 MHz.

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 816

10/12/14 BIT 10 TO 65 MSPS DUAL ADC