Analog Devices AD9768 Datasheet

Ultrahigh Speed IC

FEATURES 5 ns Settling Time 100 MSPS Update Rate 20 mA Output Current ECL-Compatible 40 MHz Multiplying Mode

APPLICATIONS Raster Scan & Vector Graphic Displays High Speed Waveform Generation Digital VCOs Ultrafast Digital Attenuators

GENERAL DESCRIPTION

The Analog Devices AD9768SD D/A converter is a monolithic current-output converter which can accept 8 bits of ECL-level digital input voltages and convert them into analog signals at update rates as high as 100 MSPS. In addition to its use as a standard D/A converter, it can also be utilized as a two-quadrant multiplying D/A at multiplying bandwidths as high as 40 MHz.

An inherently low glitch design is used, and the complementary current outputs are suitable for driving transmission lines directly. Nominal full-scale output is 20 mA, which corresponds to a 1 volt drop across a 50 Ω load, or ±1 volt across 100 Ω returned to +1 volt. The actual output current is determined by the on-chip reference voltage (V current setting resistor, R

Full-scale output current I calculated with the equation:

The setting resistor R both have low temperature coefficients. A complementary

is also provided.

OUT

SET

OUT

=4×

OUT

and the output load resistor should

SET

< –1.26 V) and an external

REF

with digital “1” at all inputs is

RET–VREF

SET

D/A Converter

AD9768

FUNCTIONAL BLOCK DIAGRAM

The reference voltage source is a modified bandgap type and is nominally –1.26 volts. This reference supply requires no external regulation. To reduce the possibility of noise generation and/or instability, Pin 15 (REFERENCE OUT) can be decoupled using a high-quality ceramic chip capacitor. Stabilization of the internal loop amplifier is by a single capacitor connected from Pin 17 (COMPENSATION) to ground. The minimum value for this capacitor is 3900 pF, although a 0.01 µF ceramic chip capacitor is recommended.

The incredible speed characteristics of the AD9768SD D/A converter make it attractive for a wide range of high speed applications. The ability of the unit to operate as a twoquadrant multiplying D/A converter adds another dimension to its usefulness and makes the AD9768SD a truly versatile device.

AD9768SE PIN CONNECTIONS

AD9768JD/SD PIN CONNECTIONS

REV. A

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703

(typical @ +258C under following conditions unless otherwise noted; nominal digital

AD9768–SPECIFICA TIONS

Parameter Unit AD9768SJD/SD/SE

RESOLUTION(FS = FULL SCALE) Bits 8 LSB WEIGHT (CURRENT) µA78 ACCURACY

TEMPERATURE COEFFICIENTS

DIGITAL DATA INPUTS

OUTPUT

SPEED PERFORMANCE

REFERENCE

VOLTAGE-MULTIPLYING MODE4 (See Figure 2)

Differential Nonlinearity ± % FS 0.2 Integral Nonlinearity ± % FS 0.2 Monotonicity Guaranteed Zero Offset (lnitial) µA60

Zero Offset ppm/°C 1.5 Reference Voltage (–1.26 V) ppm/°C70

Logic Compatibility ECL Logic Voltage Levels “l” = V –0.9 “0” = V –1.7 Coding Binary (BIN) = Unipolar Out

Current (Unipolar) FS mA (max) 2 to 20 (30) I

(@ Pin 13)

OUT

All Digital “1” Input mA 20 All Digital “0” Input mA 0

(@ Pin 14)

OUT

All Digital “l” Input mA 0 All Digital “0” Input mA 20

Compliance V (Pin 13) –0.7 to +3.0 Impedance Ω (±15%) 750

Settling Time (to 0.2% FS) Slew Rate V/µs 400 Update Rate MSPS 100 Rise Time ns 1.8 Glitch Energy pV-sec 200

Internal, Monolithic External, Variable

Voltage-Multiplying Mode V (max) 0 to –1.1 (–2) Current-Multiplying Mode mA (max) 0 to –5 (–7.5 )

VM Range (at Pin 16) V ± 0.5 VM Center V –0.6 Resistance (at Pin 16) kΩ 800 Transfer Function – Measured at Pin 13; Digital “0” Applied

Large Signal Bandwidth (–3 dB Point) kHz 250

Offset Binary (OBN) = Bipolar Out

V (Pin 14) –1.1 to +3.0

ns 5

V –1.26

to Bits 1-8: –0.1 VM Input = 0 mA I –1.1 VM Input = 0 mA I Measured at Pin 13; Digital “1” Applied to Bits 1-8: –0.1 VM Input = 1 mA I –1.1 VM Input = 20 mA I

input levels; nominal power supplies; RL = 50 V; R

OUT OUT

OUT

= 220 V; V

SET

RET

= 0 V)

Parameter Unit AD9768SJD/SD/SE

CURRENT-MULTIPLYING MODE

(See Figure 4)

IM Range (at Pins 17 & 18) mA 0 to 5 Resistance (at Pin 18) Ω 160 Transfer Function – Measured at Pin 13; Digital “0” Applied

Large Signal Bandwidth (–3dB Point) MHz 40

POWER REQUIREMENTS

–5.2 V ±0.25 mA (max) 66(70) +5.0 V ±0.25 mA (max) 14(15) Power Dissipation mW (max) 410(430) Power Supply Sensitivity

TEMPERATURE RANGES

Operating

AD9768JD °C 0 to +70 AD9768SD/SE °C –55 to +125

Storage °C –55 to +150

THERMAL RESlSTANCE

Junction to Air, θJA (Free Air) °C/W 90 Junction to Case, θ

PACKAGE OPTION

Ceramic (D-18) AD9768JD

LCC (E-20A) AD9768SE

NOTES

Relative to FS, including linearity (within voltage compliance limits).

Worst case settling time; includes FS and Most Significant Bit (MSB) transitions.

Applies when operating AD9768 as standard D/A.

Based on RL = 50 ohms; R

1% change in either power supply voltage causes 0.07% change in analog output.

Case temperature.

Maximum junction temperature 125°C.

D = Ceramic DIP, E = Leadless Ceramic Chip Carrier.

Specifications subject to change without notice.

= 220 ohms; V

SET

to Bits 1-8: 1 mA IM Input = 0 mA I 5 mA IM Input = 0 mA I Measured at Pin 13; Digital “1” Applied to Bits 1-8: 1 mA IM Input = 4 mA I 5 mA IM Input = 20 mA I

OUT OUT

OUT

%/% 0.07

°C/W 20

AD9768SD

= 0 V.

RET

AD9768SD D/A Schematic

–2–

REV. A

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