Rainbow-electronics MAX5887 Manual de usuario descargar pdf (Pagina 10)

MAX5887

3.3V, 14-Bit, 500Msps High Dynamic

Performance DAC with Differential LVDS Inputs

10 ______________________________________________________________________________________

plane, IOUTP should be selected as the output, with

IOUTN connected to AGND. Note that a single-ended

output configuration has a higher 2nd-order harmonic

distortion at high output frequencies than a differential

output configuration.

Figure 3 displays a simplified diagram of the internal

output structure of the MAX5887.

Clock Inputs (CLKP, CLKN)

The MAX5887 features a flexible differential clock input

(CLKP, CLKN) operating from separate supplies

(VCLK, CLKGND) to achieve the lowest possible jitter

performance. The two clock inputs can be driven from

a single-ended or a differential clock source. For sin-

gle-ended operation, CLKP should be driven by a logic

source, while CLKN should be bypassed to AGND with

a 0.1µF capacitor.

The CLKP and CLKN pins are internally biased to 1.5V.

This allows the user to AC-couple clock sources directly

to the device without external resistors to define the DC

level. The input resistance of CLKP and CLKN is >5kΩ.

See Figure 4 for a convenient and quick way to apply a

differential signal created from a single-ended source

(e.g., HP 8662A signal generator) and a wideband

transformer. These inputs can also be driven from an

LVDS-compatible clock source; however, it is recom-

mended to use sinewave or AC-coupled ECL drive for

best performance.

Data Timing Relationship

Figure 5 shows the timing relationship between differ-

ential, digital LVDS data, clock, and output signals. The

MAX5887 features a 1.8ns hold, a -0.8ns setup, and a

1.8ns propagation delay time. There is a 4-clock-cycle

latency between CLKP/CLKN transitioning high/low and

IOUTP/IOUTN.

LVDS-Compatible Digital Inputs

(B0P–B13P, B0N–B13N)

The MAX5887 features LVDS receivers on the bus input

interface. These LVDS inputs (B0P/N through B13P/N)

allow for a low-differential voltage swing with low con-

stant power consumption across a large range of

0.1µF

1.2V

REFERENCE

10kΩ

REF

SET

DACREF

FSADJ

REFIO

REF

= V

REFIO

SET

CURRENT-STEERING

DAC

IOUTP

IOUTN

Figure 2. Reference Architecture, Internal Reference

Configuration

OUT

IOUTN IOUTP

CURRENT

SOURCES

CURRENT

SWITCHES

Figure 3. Simplified Analog Output Structure

SINGLE-ENDED

CLOCK SOURCE

(e.g., HP 8662A)

1:1

WIDEBAND RF TRANSFORMER

PERFORMS SINGLE-ENDED TO

DIFFERENTIAL CONVERSION.

DAC

CLKP

0.1µF

CLKN

CLKGND

25Ω

Figure 4. Differential Clock Signal Generation

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 16 17 18

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