MAX5018 데이터 시트보기 (PDF) - Maxim Integrated

부품명

상세내역

일치하는 목록

MAX5018

8-Bit, High-Speed DAC

Maxim Integrated 

8-Bit, High-Speed DAC

_______________Detailed Description

The MAX5018 is an ultra-high-speed video digital-to-

analog converter (DAC) capable of up to 275Msps con-

version rates. This high speed makes the device

suitable for driving 1500 x 1800 pixel displays at 70Hz

to 90Hz update rates.

The MAX5018 is separated into different conversion-

rate categories, as shown in Table 1.

The MAX5018 has ECL logic-level-compatible video

controls and data inputs. The complementary analog

output currents produced by the devices are propor-

tional to the product of the digital control and data

inputs in conjunction with the analog reference current.

The MAX5018 is segmented so that the input data’s

four MSBs are separated into a parallel thermometer

code. From here, fifteen identical current sinks are driv-

en to fabricate sixteen coarse output levels. The

remaining four LSBs drive four binary-weighted current

switches.

MSB currents are then summed with the LSBs that con-

tribute one-sixteenth of full-scale to provide the 256 dis-

tinct analog output levels.

The video-control inputs drive weighted current sinks,

which are added to the output current to produce com-

posite video-output levels. These controls (sync, blank,

reference white (force high), and bright) are required in

video applications.

A feature that similar video DACs do not have is feed-

through control. The feedthrough pin (FT) allows regis-

tered or unregistered operation of the video control and

data inputs. In registered mode, the composite func-

tions are latched to the pixel data to prevent screen-

edge distortions (generally found on unregistered video

DACs).

Table 1. The MAX5018 Family and

Speed Designations

PART

MAX5018A

MAX5018B

UPDATE

275Msps

165Msps

COMMENTS

Suitable for 1200 x 1500 to

1500 x 1800 displays at

60Hz to 90Hz update rate.

Suitable for 1024 x 1280 to

1200 x 1500 displays at

60Hz to 90Hz update rate.

__________Applications Information

General

Figure 1 shows a typical application using the MAX5018

in a color-raster circuit. The MAX5018 requires few exter-

nal components and is extremely easy to use. The

MAX5018’s very high operating speeds require good cir-

cuit layout, supply decoupling, and proper transmission-

line design. For best performance, note the following

considerations.

Input Considerations

Video-input data and controls can be directly con-

nected to the MAX5018. Note that all ECL inputs are

terminated as closely to the device as possible to

reduce ringing, crosstalk, and reflections. Maxim rec-

ommends that stripline or microstrip techniques be

used for all ECL interfaces. A convenient and common-

ly used microstrip impedance is about 130Ω, which is

easily terminated using a 330Ω resistor to VEE and a

220Ω resistor to ground. This arrangement gives a

Thevenin-equivalent termination of 130Ω to -2V without

the need for a -2V supply. Standard single in-line pack-

age (SIP) 220/330 resistor networks are available for

this purpose.

Figure 2 shows equivalent input circuits.

Output Considerations

The analog outputs are designed to directly drive a

dual 50Ω or 75Ω load-transmission system as shown in

Figure 1. The MAX5018 output source impedances are

high-impedance current sinks. The load impedance

(RL) must be 25Ω or 37.5Ω to attain standard RS-343-A

video levels. Any deviation from this impedance affects

the resulting video output levels proportionally. As with

the data interface, it is important that all analog trans-

mission lines have matched impedance throughout,

including connectors and transitions between printed

wiring and coaxial cable. The combination of matched

source-termination resistor RS and load terminator RL

minimizes reflections of both forward and reverse trav-

eling waves in the analog transmission system.

Power Considerations

The MAX5018 has two analog power-supply pins and

operates from a standard -5.2V single supply. Proper

supply bypassing augments the MAX5018’s inherent

supply-noise-rejection characteristics. As shown in

Figure 1, each supply pin should be bypassed as

close to the device as possible with 0.01µF and 10µF

capacitors.

_______________________________________________________________________________________ 5

Share Link: